POWERED INTERCOM

AZAHARI BIN MORSHlDI

Universiti Malaysia Sarawak 2000

TK 78815 A992 2000

P KHl OMA r M AKLUM A T 1 hilI1AI a~lul1l1 U d~IlI~ I IJK~I II ~1 L t

[[[I [[ ii [[~ [I1[~[j~l[n[[ ~I [[ [ 1 [[1111 0000 0 8 1 657

POWERED INTERCOM

Z II-IH BI lOR HIOI

Tcsis DI~emukakan -tpada Fa~lIlt i keJumtcraaJl Unler~iti 1 a la~sia SaraW k

Scbagai McmClluhi Seballagian danpada Syarat Penganllgcrahan SarJan~ Muda KeJ unllcraan

Dengan Kepujian (KeJuruleraan Elcktronik dan Telekol11l1nikasi) 2000

--- shy

Borang Penyeruha n rcsis l ni(~r$iti ~tal ~sia Sara

BORANG PE~ YERA HAN TESI S

Juuu l POIercd In terc o m

SEl-IIrIGAn~l _ _ 97middotlt)8-_____

Say AZ l iAR] 6 1 IORSIIiDI (HI Rl F Br~AR)

111Cftgalu rncmbcnarbn 1i~S Inl dlompall dl Pu()1 joJIIClma 1ai lumllt Aildcmil LunCfIl1t Milla~~13 ~arn ~ dcngdO ~ aralmiddots~ arat 1cgunun 501)111 hen~UI

1i3lnnhk 1~r1~S PfOJcI adJlm dl bouh nama pcllull5 mchllillan penuh~1 soJb3S]1 prOj hCriamJ dan dlh l3OI alel U~Il middotS blmlll~na ~tlal 11 Icpunyaan UN It )

2 N3dhl1n Salmun d dJlnm bcnlUI kCr1JJS ill UI rm lni ham a bolLh lil hu l deuSlIn ~clxnargtl ll Ixnuli J ndJ JKnuJis

J Puoo t KhlWllCU r- 1L(UlULIt ad~(lIil II IMAS dibc bullbull arian mCnlbLlJt ~aJmm wlNL pCllgaJIbullbull 11 IIIcrdl 1113 pmji hama holch Ihterhnl311 dClIgi3l1 kcbcnnnlll ~nuhs Oayaran lQ~ all1 3dnlnh rncngtlut ladl1f

~ J ng dIPCrSCIUJUIlclll) bull (ja tnCmhJUll11Uido mCll1bCIIJrlall Il~rpUSlltlI~aI1 l11Cmbu)[ salman h~1111~ IUUJll Uti IbJ~n b1hlll pcnu~aran III lIn1ara nllluSl JX-1Igullan IlnaJ i

h bullbull S13 Io1l1dIlln l )

c=J ~IIIT I r1cngandUJlgl l1l al1 Utllot ~ nng bcrtblJlh 1l~luma(an Olau ~c(lCnun~Jn

~13Il~~t3 ~pcm ~an8 lcmlalluh dt daltm middotIA kAHsr RAt ll ~t71l

[=J TER HA lJ I~ lcngdlldunBi mlIum-a t 1 ERHAD -13 IdAI dd-ntuLtn old orKoOlSlI bold bullbull d IlljUiot rcnclldlbn djJlanhallJ

~ TlDAK ITRHAl)

D-hlan kh

__-==ltl~-cl~ J TAM)ArANGAt- r[NUI IS ) (T~NDATANGA)J lfYF I IA

I S42 [()rollg G I

En A J -~ha ljd OUlIlllln

Tankh

PI(ln~ ~Ol liOik b ntn n 1n1II Mn t Pmek Ini SI l rl a bu T EI-tIlltO ~ 1 1l IlImplrln Unit Ib ripuhl p ihllk hCrIuuJ orttll ni-fh l hcdcnnn drn~ltn m(n~(nll klo )(I lI h 1tll1 pob nil proj eJ In i wri u m dhktln ~h~lIi ~U l IT l11I1J rERUAI)

P KHl OMA r M AKLUM A T 1 hilI1AI a~lul1l1 U d~IlI~ I IJK~I II ~1 L t

[[[I [[ ii [[~ [I1[~[j~l[n[[ ~I [[ [ 1 [[1111 0000 0 8 1 657

POWERED INTERCOM

Z II-IH BI lOR HIOI

Tcsis DI~emukakan -tpada Fa~lIlt i keJumtcraaJl Unler~iti 1 a la~sia SaraW k

Scbagai McmClluhi Seballagian danpada Syarat Penganllgcrahan SarJan~ Muda KeJ unllcraan

Dengan Kepujian (KeJuruleraan Elcktronik dan Telekol11l1nikasi) 2000

--- shy

Borang Penyeruha n rcsis l ni(~r$iti ~tal ~sia Sara

BORANG PE~ YERA HAN TESI S

Juuu l POIercd In terc o m

SEl-IIrIGAn~l _ _ 97middotlt)8-_____

Say AZ l iAR] 6 1 IORSIIiDI (HI Rl F Br~AR)

111Cftgalu rncmbcnarbn 1i~S Inl dlompall dl Pu()1 joJIIClma 1ai lumllt Aildcmil LunCfIl1t Milla~~13 ~arn ~ dcngdO ~ aralmiddots~ arat 1cgunun 501)111 hen~UI

1i3lnnhk 1~r1~S PfOJcI adJlm dl bouh nama pcllull5 mchllillan penuh~1 soJb3S]1 prOj hCriamJ dan dlh l3OI alel U~Il middotS blmlll~na ~tlal 11 Icpunyaan UN It )

2 N3dhl1n Salmun d dJlnm bcnlUI kCr1JJS ill UI rm lni ham a bolLh lil hu l deuSlIn ~clxnargtl ll Ixnuli J ndJ JKnuJis

J Puoo t KhlWllCU r- 1L(UlULIt ad~(lIil II IMAS dibc bullbull arian mCnlbLlJt ~aJmm wlNL pCllgaJIbullbull 11 IIIcrdl 1113 pmji hama holch Ihterhnl311 dClIgi3l1 kcbcnnnlll ~nuhs Oayaran lQ~ all1 3dnlnh rncngtlut ladl1f

~ J ng dIPCrSCIUJUIlclll) bull (ja tnCmhJUll11Uido mCll1bCIIJrlall Il~rpUSlltlI~aI1 l11Cmbu)[ salman h~1111~ IUUJll Uti IbJ~n b1hlll pcnu~aran III lIn1ara nllluSl JX-1Igullan IlnaJ i

h bullbull S13 Io1l1dIlln l )

c=J ~IIIT I r1cngandUJlgl l1l al1 Utllot ~ nng bcrtblJlh 1l~luma(an Olau ~c(lCnun~Jn

~13Il~~t3 ~pcm ~an8 lcmlalluh dt daltm middotIA kAHsr RAt ll ~t71l

[=J TER HA lJ I~ lcngdlldunBi mlIum-a t 1 ERHAD -13 IdAI dd-ntuLtn old orKoOlSlI bold bullbull d IlljUiot rcnclldlbn djJlanhallJ

~ TlDAK ITRHAl)

D-hlan kh

__-==ltl~-cl~ J TAM)ArANGAt- r[NUI IS ) (T~NDATANGA)J lfYF I IA

I S42 [()rollg G I

En A J -~ha ljd OUlIlllln

Tankh

PI(ln~ ~Ol liOik b ntn n 1n1II Mn t Pmek Ini SI l rl a bu T EI-tIlltO ~ 1 1l IlImplrln Unit Ib ripuhl p ihllk hCrIuuJ orttll ni-fh l hcdcnnn drn~ltn m(n~(nll klo )(I lI h 1tll1 pob nil proj eJ In i wri u m dhktln ~h~lIi ~U l IT l11I1J rERUAI)

Borang Penyeruha n rcsis l ni(~r$iti ~tal ~sia Sara

BORANG PE~ YERA HAN TESI S

Juuu l POIercd In terc o m

SEl-IIrIGAn~l _ _ 97middotlt)8-_____

Say AZ l iAR] 6 1 IORSIIiDI (HI Rl F Br~AR)

111Cftgalu rncmbcnarbn 1i~S Inl dlompall dl Pu()1 joJIIClma 1ai lumllt Aildcmil LunCfIl1t Milla~~13 ~arn ~ dcngdO ~ aralmiddots~ arat 1cgunun 501)111 hen~UI

1i3lnnhk 1~r1~S PfOJcI adJlm dl bouh nama pcllull5 mchllillan penuh~1 soJb3S]1 prOj hCriamJ dan dlh l3OI alel U~Il middotS blmlll~na ~tlal 11 Icpunyaan UN It )

2 N3dhl1n Salmun d dJlnm bcnlUI kCr1JJS ill UI rm lni ham a bolLh lil hu l deuSlIn ~clxnargtl ll Ixnuli J ndJ JKnuJis

J Puoo t KhlWllCU r- 1L(UlULIt ad~(lIil II IMAS dibc bullbull arian mCnlbLlJt ~aJmm wlNL pCllgaJIbullbull 11 IIIcrdl 1113 pmji hama holch Ihterhnl311 dClIgi3l1 kcbcnnnlll ~nuhs Oayaran lQ~ all1 3dnlnh rncngtlut ladl1f

~ J ng dIPCrSCIUJUIlclll) bull (ja tnCmhJUll11Uido mCll1bCIIJrlall Il~rpUSlltlI~aI1 l11Cmbu)[ salman h~1111~ IUUJll Uti IbJ~n b1hlll pcnu~aran III lIn1ara nllluSl JX-1Igullan IlnaJ i

h bullbull S13 Io1l1dIlln l )

c=J ~IIIT I r1cngandUJlgl l1l al1 Utllot ~ nng bcrtblJlh 1l~luma(an Olau ~c(lCnun~Jn

~13Il~~t3 ~pcm ~an8 lcmlalluh dt daltm middotIA kAHsr RAt ll ~t71l

[=J TER HA lJ I~ lcngdlldunBi mlIum-a t 1 ERHAD -13 IdAI dd-ntuLtn old orKoOlSlI bold bullbull d IlljUiot rcnclldlbn djJlanhallJ

~ TlDAK ITRHAl)

D-hlan kh

__-==ltl~-cl~ J TAM)ArANGAt- r[NUI IS ) (T~NDATANGA)J lfYF I IA

I S42 [()rollg G I

En A J -~ha ljd OUlIlllln

Tankh

PI(ln~ ~Ol liOik b ntn n 1n1II Mn t Pmek Ini SI l rl a bu T EI-tIlltO ~ 1 1l IlImplrln Unit Ib ripuhl p ihllk hCrIuuJ orttll ni-fh l hcdcnnn drn~ltn m(n~(nll klo )(I lI h 1tll1 pob nil proj eJ In i wri u m dhktln ~h~lIi ~U l IT l11I1J rERUAI)

--

l -jlIA S 15OC 02

27 Inc uO()

Pcnguru Pw nt KIi J111 il t Mak lul11a t Abdc111ik Unive rsili Malaysia Sarawak

P lIJIL

Tcs is pellljar - iha ri Bin Morshilli

Tesis p~laiar ini adalah dikategorikan sebagai tes is terhad se lal11a I tahUI1_ In i adaluh ke rana makl1l111at yilng tc rk andu ng mcrupakan nwk ilimal sc benlr _iabatun kcrajaan di mana ka iian di buat

l~ ian _ te rima kasih

- rlrJ~K HI DMAT l NTUK NEG ARA-

Ya ng be nar

~~ En AImiddotK halid Hi Olhm 1n Kellla Program Kcjurlilc raan Eleklroni k dan Teleko mllnikasi

b_p_ Dekan

-

Perakuan Penye l ia

Tes is illi lelah d ibaca dall d isahkJ n okh

_----6-~ cJ lt (~ ILOOO

Ln i-Khalid Hj Olhman Penye ii(l

Acknowledgement

First of a ll I would like to tban k to God fo r giVin g me the sl r~J1 h i lJ1d

a bility to comple te the report a nd project for a bout 2 cmcstcrs A lo t of

c hallenges and prob le ms have been encountered dU rin g Ih e resea rches a nd

implementation o f the project No t forgotte n my beloved fDmi l ~ fu r gi in c lhe

morale supports and e ncou rltlgement Without the m Il IS middotltIY rilllllul t lor 11K

to handle the s itu a tions I wou ld a lso like to express m y grn ltudc to tI( people

wh o a r e In volved in th e project e it her it is direct ly o r mdll n Ilv e ~r(C I tlly l iJne

who are n amed belowshy

0 Kad im S u a idi (Dean of Engineering)

Mr AI-Kh a lid Hj Othman (Lecturer a nd S upe rvisor)

En Wan Abu Bakar amp En Zakana (l ab Assistants)

Mo reover I wou ld a lso like to take this opportllnilv 10 Ih lnk lo th e

u ndergradu ate sch olar s tudents under Faculty o f Engil eel illl Imiddot-ho hn I rcd

the report an d gave good comm en ts Thank you

ABSTRACT

Powered In Llt com is one of the n ew techn ologies 111 r l~ (ntn munic] OJ)

sys tem It m eans that the intercom is usin g th e power suppl) for the medium

It is mo re s imilar to the wireless intercom wh e re th ere is 11 lt) n ec middotd of c ~ rr

cables or technical kil to link to the other inte rcoms PowfTcd inlCleom -1

transmit and receive th e data in bo th way but not ll the Sl lnc me il If

duplex) Powered intercom is SUItab le use for house a nd dbo nice where 11ll

distance between the intercom is about 1500 fee l The po-elcrlI11IC I(Om 11 J

channels which it can be a dded up to 8 ch ann el (most appropnll() FCT

ch a nne l can communicate with each oth er by chmgin f Illl dl ~l l1 lwl smiddot Ilc h

Thus i t is more re liable rather th a n the presen t in tercom here- there is onl

one (m aster) which can con tac t the o thers hile the re~1 ol lv rltccI e I he dJW

(multiplexe r system) For further details about lhe ffCl tl1res a pp lic rio n d(s

circuils a nd im plementation for the Powered inlercom ill be lu cil ell a ll dzed

and wi ll be di sc u ssed in th is report

-- --

ABSTRAK

_

Powered intercom adalah salah smu tekno logi wg l(f hal ll d ldm

sistem kOlTIllnikasi Dengan erti kata lalll ia men of(u nalcan Sl lmbtT k il(lgtltl

sebagal medium perantaraan La m enyerLtp a l dcnf~an in l t J(ol n t rlrl p I rl r

dim ana kabe l dan kebolehan tekmkal tidak dipcrlukan d ll) m pCIW Jlll buJl111

a nt ara in tercom dengan yang lain Powered inlercom bolch rncng h l l] r eLm

m cncri m a data te lapi tidak di daJam satu m asa (scparu h d uplex) 1T[(ci

inte rcom a m a t sesu a i untuk kegunaan di rllmah ulLl pejltJiJd l d im altl j II ilk

antara satu intercorn dengan yang lain ialah ki ra -kJra 1500 k ltJl i ra JU Jl

m empllnya i 3 salura n dimana ia bolh ditingka tka n sebanya k S salu rall (ami l

sesuai) Setiap salUl-an boleh menghublln gi anta ra s at Lt sami Llin des

m en ukarkan s ui sn ya Olch itu ia lebill berkesan b Ibcll1 ci IllR 1 11 [( s ed 1lt11

dimallCl h anya satu yang dapat men ghantar dla Unt lrl m d dll lll] l

selanjutnya m engenai ciri-ClIi aplikasi dan pCmaS8 I1~ltHl a ka n ~lthT-llgk an ltlgi

el i d a lam laporan in

IUltI hrdmRI ~hklurnal ~adtl1l1 11 tK 111 Ml ~ - AI 1_

Conte nt

Chapt e r 1 Introduction

11 Introduc tion 12 Objectives an d a im of the project

Cha pt e r 2 Lit e r a ture Review

2 1 2 1 2 12

2 2 2 21 22 2 22 3 22 4 225

23 2 3 1 232

24 24 2 4 2

2 5 25 1 252

26 26 1

Wha t is communication Block Diaf middotam C h an n el Charac te ristics

Baseba nd s ign al types An a logu ej Digi tal sIgn als Base band and tcrmmalogy Class ification of modula tion types Advantages modu lation Analogue modulation

Multiplexing Frequen cy Trans mitte r Autom o tic Frequency Control of FM gene ral()r

Frequen cy Modula ted Radio Receiver Genelmiddotal Compon ent Des ign

Di s to rti o n And Noise Delay Di sto rtion No ise

Sign a l to No ise Ra tio Baseba nd System s

Page

2

1(1

I I 14 14 14

16 20 )_

J 1 14

11 c7

4

32

Chapter 3 Schematic Design and Components

3 1 SchematJc Design Components and Block diagram

Chapter 4 Results and Analysis

4 1 Power Supply 2 C-MOS Digital inverter (CD 4069)

43 Tone Decode r (LM567) 44 Audio Amplifier (LM386)

45 Outpu t of th e system

Conclusion and Recommendations Chapter 5

511

59

(0 62

11 )

hll 71

7 2

List of Figures

Figure Description Page

2 1 Block d iagram of communi cation sys te m

22 0 Classes o f s ign al I I

22 1 Frequ ency Divis ion MuJti plex concept IIgt

222 Frequen cy Division Multi p lexing

(a ) FM (b)FDM (c) Baseband s pctrum lY

23 1 Basic FM Generato r 21

2 32 Im proved PM Generato r l

233 PM gen erator wilh AFC circu it 2 1

234 Block d iagram of Lim ite r r ~-

235 Diagram uf Preampli fier 26

2 36 Im provement of symmetric clippe r 27

2 3 7 Charac teri s tic of frequen cy to am pli tude H

2 38 The u se of double-tu ned circui t 30

bull 124 1 Block d iagram of domes tic recelver ~

242 Fosley Seeley Discrimina lo r 3Y

243 Diagra m of Quadrature de tec to r -to

2 4 4 Phase shift 4 1

245 Block d iagram of gtbase Locked loop 43

25 I Typicl l ifferentlal de lay H

252 Typical Amplitu de vs Frequency respon se 46

255 Probabili ty of Bit Erro r in

261 Baseband System 33

57Schem a ti c Design O [ Powered In te rcom3 0

- 1 3 1 1 Block diagram o[ in tercom system shy

4 1 0 (a ) Sch em a ti c power s upp ly

roIb) Physical -ollage regulator

6 4 1(a) Inpu t powe r s u p ply s ign a l

6 1 4 J (b) Outpu t s ignal

024 2(a ) Gate tra n s fer

142 ()) Power d iss ipa tion vs Frequ ency

42(c) S ign a l Input of inve rter 03

1)442(d) S ignal oUlput of inverte r

(54 3 (a ) S ign al mput of lone decode r

fgt)4 3 ()) S ign al of ca pac itor timin g

6r43(c) S ignal of resistor tim ing

Uh43 (c) S ign al [ter through 2 K res is to r

(I4 3 (e) S ig11 a l after throu gh 2 2 K resisto r

h7 Signal after thro ugh 27 K res is tor 43(f)

(g43(g) Outp u t of tone decod er

6944 I(a) Inpu t (+) of ampli fie r

4 4 lib) In pu t ( ) of ampli fi er I))

44 I (e) Ou tput Sign al of a mplifie r 70

70 44 fel) VolLage source of amplifi er

4 5 Sys te m ou tput s ignal 7

List Of Tables

Table Dcscript Ion

9Frequency band21

12 22 1 Types of Baseband Signal

253 Requirement fo r two or mUltipoint 46

254 Requirem ent for two or multJ point for

47Envelope del ay distortion

Chapter 1

Introduction of Powered Intercom Project

Introduction

A vast n e twork telecommunicatIOn llllks spans tltc in duS Trilaquolt zcd

COU ntne of the world carrymg telephone te legraph tclcvi ion n e5

p h ologra phs a nd ra dio programs ThIS n e twork IS con stro n llv heing

exp a nded a nd n ew invention s are increasin g its capaCIty ltIt breathtnllt lI1g

ra te The re were m any proble ms we have en cou ntered in th e bq~i l I inf( bu t

s lowly soluti on s have been found We have learn ed to li se the IlI1 llts m o re

e ffi c ie ntly a nd th e cos ts have dropped dramatIc a lly Nowodays there ltIre

m a n y typ es of links that has been use d to com mUI1lCCllr an ti Ilslng the

power su pply to co mmunicate is a new method

Inter com technology has been found 111 ea rlv 1 9~) Os ami s lowl It s

b een expanded to be used in local area network nor WIde lea network

Powered inter com is a new technology where It is slmi l r to lIinkss

intercom However wlreless lntercom IS a system there ~() Ineo n e C(Ul

communicate w1th each other 111 the same small a r ea (h ousr n bllil cll llg)

without using wire d links but for powered intcrcnm SOIneon e ju s t need to

plu g it to th e power supply without worryll1g on h ow to lin k the Inl r](om

By u s ing thi s techno logy it is more con venien t for the c u stomer tu put the

in tercom system s w ith ou t worrym g how to Ill s t ltl ll (mess) w lr(d) and n1lll(

o rganized Neve rtheless a lot o f problems to imple m ent this 1lt11lc o f

sys te m s

For th IS thesis the c haracteris tics on th~ powtrn ml errC)m ~11 1 hI

s tudied befo re Implement the product Neve rth eless thi S repo rt is Iso

s tudy case all the advan ced of telecommuI1Ication s

Chapter 2

Literature Review of Powered Intercom Project

21 WHAT IS COMMUNICATION

211 THE BLOCK DIAGRAM OF A COMMUNICATION SYSTEM

Fi gure 20 shows a cOllullonly used model Il) 1 Cl l l ll 1l l J11 iCl li u ll sy --lun

-l lhough it - lIggcsls a system -or cOllllllunicaLion be1ccn t u ICllhdCh InL~I(t d

or sonar In I hich Ihe system input and output 111 1 be localed 11 Ihe 11e ie

Regardless of the particular application and conli gu-iln II 11l1l1 lmli

trallsmission systems invariably involve three lllZljor sUbSYS tlll l ~~ 11l1bIl1lIloCl Ihl

channeL and d receiver In this literature review we II I lI s lul l bmiddot I h lllkill ~ t11 LLrI1l S

01 systems ror transk r of inforlllation between rcmolch IIK ll ed poi nls II is

limited to such systellls

mes sage message

sgnat

Inp~Jt

transducer T fansmlU8r

carner

Iransmll signal

R8C81ver

addl11ve nOise Interfereflce dls tNtlon res lJolllng from ba~d limlitl119 and non Ilns-cHllls S

c u lpu t ~IJnal

OIJIPll t jrr1sJu cer

Fig 2 I Block d iagram of a communic8 tion sys lcm (Rl fc 10 Re k l llU IIII

2111 Input Transducer

The vide vanety of possible sources of informatlOn refmiddota lll S III ffi JIlV (11 1 h 1r11 1

[arms [or mess a pes Regardless of their exa c t form hOW (lr IncSS rq~~e s 1Tl1 ~

be categorized as analog or digliol The former tTl) be 1ll 1l(lt-lt- cJ s fU Il CIIlt1I 1S

of a continu ous-time variable ([or example press u re t ll n pcrdl lll4 spLrch

mus iC l whereas the latter consist of discrete symbols (for rX d rnpk 1 nlt tl

text) Almost lIwanably the message produced by a sOll rce mbl be

converted bv a transducer to a for m SUItable for til c p ltrti cul r I pe f

cnrn mU111Calion system employed For CX2lillplc 111 elre t riri11

com tT1urlicarions speech waves are converted b cl nllCiUphullf Lo nll ~e

variatIons Sucl a converted 11leSsage is referred to as 111( Incssnrlf siqnu

In thi s book therefore a signal can be Interpreted as the tmiddotu idtin l1 01 a

qua n tIty often a vOlt2gC or current with ti me

2112 Transmitter

The purpose of the transmitter is to couple the mc~sI1~ Lo Llw ~ (Inll c l

Altho ugh it is not uncommon to find the input transd u ce l dll l c lv u lu plcc1

to the trans111ission medium as for example in some interLonl s stC1l1~ iL is

often nccessary to modulate a carrier wave With the s lgn 1 flillTI tile 1111111

transducer Modulation is the systematic vanation 0 1 some illlni) u ll o f Ill

carrier such as amplitude) phase or frequency in alc nrd d l1Ce 1111

function of th e n1essage slgnal There are several reasons f(gt r 11 ing (~rncr

and modulating it Important ones are (l l for ease of ra ci lduo n 1 10 red u ce

noise and interference (3) for channel assignment (4 ) for m Ultiplex ing or

transmlssion of several messages over a single chnnnc1 ln cl (5 I f J U VL rCO ITI l

equipment limitations Several of these reasons are scJf-explanHory Olhns

such as the second ill become more mcaningfui later

In additIOn to modulation other primary functions performed by the

transmi tter a r c fil tering amplillcation and coup ling th e moct u[ed s ipnaJ tu

the channel Ifor example through an antenna or o th e r 1 pprl1 pr JIC c ( ICT I

4

PIIlt1II Ihidmftl lJaklumul H~drlUil Unl c r Sl ll Nl 1aV S1lt1 S arn~n k UNIVEllt~nl MILnSr ~~ w

2 11 3 Channel

Tl w channel can have m any different for m s the most [amil iaL pc-h p is

rh e channel that exists between tlI e transmittin g an ten n a nl ) c OlTImLrLlnl

radio s tat ion and the receivIng antenna of a rad i() 111 thi 5 ch ~ nIH1 the

transmitted slgn al propagates through the 8 trn ospllfr e Dr fn e s Pju rr t il e

receli1ng antenna Hoovever it is not uncommon to Jlnd lhl~ trlnnlI1lcr

hard-wired to the receiver as in most local te lephone syste m s Th S -hlnnl

is vastly differen t from the radio example However ~ I ~ htnncls hC1H )lIe

th ing in common the signal undergoes d egradation fn ln lld I1 S ll11 tr f 1 I

receiver Although this degradatIOn may occur at ~m POlllt or 1I

communication system block diagram lt is customan iy i1 S S~t( l ~ llC d t th lil t

channe1 alone This degrad a tion often results from nOl sc rll rl qhr r lin(lt-

on-ed signals or lIlterference but also may lIlclude o lh er (hSLO I UOll cllcLh 1S

Nell such as fad lng signallcvels multiple transIniss io n P ill-h s 8nd fillr nnf

More about these unwanted perturbatIOns will be pr esented llo lll v

2114 Receiver

The receivers fu n ction is to extract the desIred messag( lrofll Imiddothe ITr-I~ I f d

signal at the ch ill1nel output and to convert It to fUI In Sl lltlhle f lll lit

output transducer Although amplification rn3 be 11IIC or ti ll IIfb l Il

atlons per[onned by the receiver especially in radio ( ()TIl11l1nllal J1) I1 ~ ) wh(n

lhe recelved Si gn al m ay be extremely weak the rn __ ~ i ll Junc lio n uf dH r L l l I C i

is to demodula ie the received signal Oft en It IS d es ire d th lI rcCCIIl rl( output be a scaled possibly delayed version of th e mcssd gc s iYIrI I I h e

modli lator mput although in some cases a morc ge n creo l rnnclo ll I Ih e

input rnessage is desired However as a result of the p re s cll (c or nO ise d nd

distortion tlus operatIOn is less than ldeal Ways of ~pprn ] hillg Illl k11

5

case of perfec t recovery wi ll be discussed as we p roceed

211 5 Output Transducer

The outpu t transdu cer completes the communicatIOn svstem This knee

converts th e el~Ll ic s Ignal at its in pu t InLO t he f rm c1csll(d hv I he svsIt m

u ser Perh aps the m os t common OUlput tran sdu cer IS 1Iucl spIkcr

However the re ar e many oth er examples s u ch as tltlpe rccorckrs pers0I w]

computers meters and cath ode-r ay tubes an d etc

212 CHANNEL CHARACTERISTICS

Noise Sources

No ise in a co mmunica tion sys tem can be cl lsslficcl Jt1 to two 1-1 lt1

categori es depend ing on its source Noise generated bv compone nt w it hll1

a co mmunication system s u ch as resis tors eicclron lubes ii nel sol U-llI(

acti ve devices is referr ed to as internal nOise The second ca tc~nr p~l( rnal

noise r esults from sources out s ide a commul11cation system 1IIclLllthr

a tmospheri c man -m a de and extrate rrestrial sou rces

Atmospheri c noise results primarily fro m SP Uri O U S )dl n wmTS

gen erated by the n a tural e lec trical d ischarges wit llll the t111uraquoph ltl

a ssocia ted with thunderstorms It is commonly rcfc rrrd to rl S 1)11( or

spitcncs Below about 100 MHz th e fi e ld s trcl12th of such radw 1 o- S IS

in ve rsely propo rtio na l to frequen cy Almosph en c II IHSC IS Lh Ii ln IZf d 011

the time do m ai n by largeamplitude s ho rt-dura tion bu rs ls lild IS nne of t illt

p rime examples o f n oise refe rred to as trl)I)[il~I(~ RecltlIlgte of llq i The

6

dependence on frequency atmospheric nOIse 8ffcrs ( CllllnWrCIltl1 A) l

broadcast radio which occupies the frequency ra n flc fm m 550 kfl lO 110

IIHiz m ore lh an it affects television and FM rd riio wlliill 11eldle in

lreq uency bands above 50 Mhz

i1a n - l11ade noise sources include high-voltage po( rl1 n ( corona dlS shy

charge COilllllUla to r-generated nOISE In electrica l lnotors aliturT10hik d

aircran 19ni t ion nOlse and switching-gear 1l00se Ign H lon n01~e (Hid

sWltching noise like atmospheric nOIse are Imru ls ivc in c Wfa uel lmpuhc

noise is Ih e predominant type of nOIse In switched vrc ll ne c hl lllwls gt11111

as lc1cphone channels For applicatlOlls such as Olee I rdJLsnli~si o I

Imp ulse noise is only an irritation factor hovrever It can 1)( ) s~ t J(Hl~

source of error in appilC3tIons involvIng transmIssion of cl lgnal el ata

Yet another importClrlL source of man -- Tn a de noist is LHlio- fr_~ qucncy

transmitters other than the one of Interest NUJSC Ju c to 1t1lcr tc nng

transmItters is commonly referred to as radlO-freq ll l1 cy in I e reTlllC( WFII

RFI IS p anicularly troublesome In SItuations 111 ~hICh i1 I ClC IIIIL dn tcllll ll IS

su bj ect to a high -density tran smitter environrrlen L -1 S Jn rnohdc

connn unications in a large city

Extraterrestrial noise sources include oLir sun and r)t l H~r ho t

heaven lv bodIes such as stars Owing to its high t Clllpcr)tlllT (tlfill(j C) md

rebliey close proximity to the earth the sun is an Intense bUI [UIIUllattiV

localized source of radio energy that extends ovcr a broad rrr-jl1lnry

spectrum Sim ilarly the stars are sources of wlde- iJalld rClth ~ntT0middot

Although m uch more distant and hence less ink n s e Ih lI1 t i l S II Il

7

nevertheless thev are collectively an importan t source o r n Oi s e IJCT 1 1 ~( n[

their vast numbers Radio stars such as quasars ltl nci p u lsm tgt t ~lbo

In l fnSe sources u f radio energy Considered a Sig ll Zll 5r1L1n c h v n~c1ln

astrCllt Omers such stars are vieved as anolher nlnSl oour( c bv

com nlun lc atlOlls l n gIneers The frequency f clngc or ~ oln r lind ( i JSIIlI C r1l)t~ C

exlends [rom a [evil megahertz to a fevv g igltlh e r t7 - 110Ih( 1 SOU l CC 01

Interference In communication systems is m u ltiple l r d ll s m ic clt)ll pt th s

These can resull from reflection off b u il d in gs th e (]rlh rp ln IK S lJleI

ShIpS or [rom refraclion by stratifications In the lranS ITlI S lt lnn Il t dlllln If

the scattering mechanism results in numerous [(fleeted (umpH1cnls be

received multipatb signal is noiselike and is ter m ed (l i(i 5e If lil e ITlUIUI l h

slgnal componen t IS composed of only one or tVO s lTnng 11 l tT tmiddotd fnv s 11 i ~

termed specular Finally signal degradatlOl1 In a corntn LtJl1 CiJ t0l1 ~ middot ~Ll nl C 1l1

occur because of random changes in attenuallOn w ilh lll 1 h e lril llSTn is SH11l

medium Such signal perturbations (disturbances) are rde n-cd Ln CiS Ji ) )

altbou g h it should be noted that specular m u itlp 1[h abo rcs llits III l l1 rlil1 ~

due to th e constructive and destructive interferen ce uf the Fltlird IIllllLlpk

signals

Typical usesFrequency Name Microwave Band (GHz)Band

Lon rnnsc n [11gnllon snnn r3 -30k l-l z c ry low frequency

Nai gatlonai 81tb rl(ilu30-300kHz Low frequen cy

IMm l imt nl liJo cli~ t I J S~ ilL Cmiddot1 11lJ1g cliree tlJ )1l flllcling COltlsl (jlla rd (( 111 111 lPnlIHLnlal IM rltIi S c IILIl m Ic c lc

nircrnfL Cllnl il l it ll

300-3000 Medium frequ en cy

ships telcgrmiddotp il tr lepllnne anu facsimd e ~llJp- flt- C iJ ~ t

3 - 30~ll-Iz High frequen cy (I-IF

VHF t eleJ~ioJl ( lhlnnltl 5 11 radio land lrdllltpOrlllinn

30-300 Very high frequency

private GHl c raft (tll t raffic cont rol laxi C Ilgt policr navlga noTlftl ltli ds

UHF tc IILgt n l hJIllll is raclto ~() n d( 11 1 I iris

03-3 Gl-lz Ultrahigh frequency 05- 10

suncd lI1lt( r ld r sw l i ite comm 1a dio ltiml le rs

20-30 30-40 40-6 0

10-2 0

s aleii lC lIlI1 lll Jldi~ alillh lc r 1l1l Cn)~1 illk~

Superhigh freq uency 60-80 3-30GI-lL

80- 100 airborn e rlc1 ar ltlpp rnarh radar middottotile r rdciar com m on

10- 124 citrrier Inn d m ollc 30-311lt] Extremel y hig h timiddotcq Rlilroad sen icc rOldOlr Iltlding

800-40 000 Infrared (80- 400) 10Hz) ~m

40k-75k Vis ible light (40-80) ~ tn Optl c01I C() llll JlL1 n11 ti (n~

GHz S vs tCln 75000- 1O~ 1 Ultrav iolet ligh t (12-40 ~ I r

G lIz wt1lltlcnq thj

Table 22 Frequ e ncy Bands With TypIcal Uses ([dc I to Reference II))

9

In ternal nOIse resu lts from th e random motIO n o f charge ca rri- in

e lect roni c com ponen ts It can be of two general types Iderrcd to s thermal

n(js e ca u sed by the random motion of free dcc rons In crmri u or or

SClnlCO n u c tor ~xci ted by th erm al agitation and shot 110 ~dtl cd by th e

runcom arrl aJ or discre te charge carriers 111 sllrh c1e lc( as lhen rllnnLc

tubes and semicondu ctor junc tion dev ices

2 2 Baseband signal types

We a re cons idering th e s ignals only a fter they have bCI OIne ek tnmiddott 1

s Igna ls s ta rt off in non-e lectncal fo rm (eg VOIce t-m per Itun) htlt 11(

been co nve rted to vo ltage u s ing some form o f tra n sdllce Ie g mluphollr middot

thermoeoll p ie)

These e lec trical sign als form the origina l Il1for lllttioll Illch i~ 10 he middot Ilt

the baseband O nce obtai ned they III always flli Il1 ln nc 01 two i)n)d

c la sses

221 Analogue signals

In these Ihe electri cal s igna l s h ows a contmu ous vari lt1l1 Ol1 II I rtmr five r a

wide ra nge of m agni tu des Ofte n th s tim e vanatton s the e Ll h tt of

an original non-elec trical signaJ (eg au preSSlll ltI nc ( I t ~gf In

microphone) so that the two arc sa Id to be ana logou s IWllce he nme of

analogue s ignal

Digital signals

IhcOsc e lec tr ica l siglla ls consi~ ( o r d iscontinuuus pu bes (or di ~It1 elel CIIIla lll ill

duc bu ciJ ltJ ngi ng tbluptl y tiom one d igi t to the nex l I lte Ire ll SI Idl ) led

S i t~lla l s as in a ld c~ prinl e r The most common type is o f cU UJC hill~ll ( lIdinL Ih Il

Perakuan Penye l ia

Tes is illi lelah d ibaca dall d isahkJ n okh

_----6-~ cJ lt (~ ILOOO

Ln i-Khalid Hj Olhman Penye ii(l

Acknowledgement

First of a ll I would like to tban k to God fo r giVin g me the sl r~J1 h i lJ1d

a bility to comple te the report a nd project for a bout 2 cmcstcrs A lo t of

c hallenges and prob le ms have been encountered dU rin g Ih e resea rches a nd

implementation o f the project No t forgotte n my beloved fDmi l ~ fu r gi in c lhe

morale supports and e ncou rltlgement Without the m Il IS middotltIY rilllllul t lor 11K

to handle the s itu a tions I wou ld a lso like to express m y grn ltudc to tI( people

wh o a r e In volved in th e project e it her it is direct ly o r mdll n Ilv e ~r(C I tlly l iJne

who are n amed belowshy

0 Kad im S u a idi (Dean of Engineering)

Mr AI-Kh a lid Hj Othman (Lecturer a nd S upe rvisor)

En Wan Abu Bakar amp En Zakana (l ab Assistants)

Mo reover I wou ld a lso like to take this opportllnilv 10 Ih lnk lo th e

u ndergradu ate sch olar s tudents under Faculty o f Engil eel illl Imiddot-ho hn I rcd

the report an d gave good comm en ts Thank you

ABSTRACT

Powered In Llt com is one of the n ew techn ologies 111 r l~ (ntn munic] OJ)

sys tem It m eans that the intercom is usin g th e power suppl) for the medium

It is mo re s imilar to the wireless intercom wh e re th ere is 11 lt) n ec middotd of c ~ rr

cables or technical kil to link to the other inte rcoms PowfTcd inlCleom -1

transmit and receive th e data in bo th way but not ll the Sl lnc me il If

duplex) Powered intercom is SUItab le use for house a nd dbo nice where 11ll

distance between the intercom is about 1500 fee l The po-elcrlI11IC I(Om 11 J

channels which it can be a dded up to 8 ch ann el (most appropnll() FCT

ch a nne l can communicate with each oth er by chmgin f Illl dl ~l l1 lwl smiddot Ilc h

Thus i t is more re liable rather th a n the presen t in tercom here- there is onl

one (m aster) which can con tac t the o thers hile the re~1 ol lv rltccI e I he dJW

(multiplexe r system) For further details about lhe ffCl tl1res a pp lic rio n d(s

circuils a nd im plementation for the Powered inlercom ill be lu cil ell a ll dzed

and wi ll be di sc u ssed in th is report

-- --

ABSTRAK

_

Powered intercom adalah salah smu tekno logi wg l(f hal ll d ldm

sistem kOlTIllnikasi Dengan erti kata lalll ia men of(u nalcan Sl lmbtT k il(lgtltl

sebagal medium perantaraan La m enyerLtp a l dcnf~an in l t J(ol n t rlrl p I rl r

dim ana kabe l dan kebolehan tekmkal tidak dipcrlukan d ll) m pCIW Jlll buJl111

a nt ara in tercom dengan yang lain Powered inlercom bolch rncng h l l] r eLm

m cncri m a data te lapi tidak di daJam satu m asa (scparu h d uplex) 1T[(ci

inte rcom a m a t sesu a i untuk kegunaan di rllmah ulLl pejltJiJd l d im altl j II ilk

antara satu intercorn dengan yang lain ialah ki ra -kJra 1500 k ltJl i ra JU Jl

m empllnya i 3 salura n dimana ia bolh ditingka tka n sebanya k S salu rall (ami l

sesuai) Setiap salUl-an boleh menghublln gi anta ra s at Lt sami Llin des

m en ukarkan s ui sn ya Olch itu ia lebill berkesan b Ibcll1 ci IllR 1 11 [( s ed 1lt11

dimallCl h anya satu yang dapat men ghantar dla Unt lrl m d dll lll] l

selanjutnya m engenai ciri-ClIi aplikasi dan pCmaS8 I1~ltHl a ka n ~lthT-llgk an ltlgi

el i d a lam laporan in

IUltI hrdmRI ~hklurnal ~adtl1l1 11 tK 111 Ml ~ - AI 1_

Conte nt

Chapt e r 1 Introduction

11 Introduc tion 12 Objectives an d a im of the project

Cha pt e r 2 Lit e r a ture Review

2 1 2 1 2 12

2 2 2 21 22 2 22 3 22 4 225

23 2 3 1 232

24 24 2 4 2

2 5 25 1 252

26 26 1

Wha t is communication Block Diaf middotam C h an n el Charac te ristics

Baseba nd s ign al types An a logu ej Digi tal sIgn als Base band and tcrmmalogy Class ification of modula tion types Advantages modu lation Analogue modulation

Multiplexing Frequen cy Trans mitte r Autom o tic Frequency Control of FM gene ral()r

Frequen cy Modula ted Radio Receiver Genelmiddotal Compon ent Des ign

Di s to rti o n And Noise Delay Di sto rtion No ise

Sign a l to No ise Ra tio Baseba nd System s

Page

2

1(1

I I 14 14 14

16 20 )_

J 1 14

11 c7

4

32

Chapter 3 Schematic Design and Components

3 1 SchematJc Design Components and Block diagram

Chapter 4 Results and Analysis

4 1 Power Supply 2 C-MOS Digital inverter (CD 4069)

43 Tone Decode r (LM567) 44 Audio Amplifier (LM386)

45 Outpu t of th e system

Conclusion and Recommendations Chapter 5

511

59

(0 62

11 )

hll 71

7 2

List of Figures

Figure Description Page

2 1 Block d iagram of communi cation sys te m

22 0 Classes o f s ign al I I

22 1 Frequ ency Divis ion MuJti plex concept IIgt

222 Frequen cy Division Multi p lexing

(a ) FM (b)FDM (c) Baseband s pctrum lY

23 1 Basic FM Generato r 21

2 32 Im proved PM Generato r l

233 PM gen erator wilh AFC circu it 2 1

234 Block d iagram of Lim ite r r ~-

235 Diagram uf Preampli fier 26

2 36 Im provement of symmetric clippe r 27

2 3 7 Charac teri s tic of frequen cy to am pli tude H

2 38 The u se of double-tu ned circui t 30

bull 124 1 Block d iagram of domes tic recelver ~

242 Fosley Seeley Discrimina lo r 3Y

243 Diagra m of Quadrature de tec to r -to

2 4 4 Phase shift 4 1

245 Block d iagram of gtbase Locked loop 43

25 I Typicl l ifferentlal de lay H

252 Typical Amplitu de vs Frequency respon se 46

255 Probabili ty of Bit Erro r in

261 Baseband System 33

57Schem a ti c Design O [ Powered In te rcom3 0

- 1 3 1 1 Block diagram o[ in tercom system shy

4 1 0 (a ) Sch em a ti c power s upp ly

roIb) Physical -ollage regulator

6 4 1(a) Inpu t powe r s u p ply s ign a l

6 1 4 J (b) Outpu t s ignal

024 2(a ) Gate tra n s fer

142 ()) Power d iss ipa tion vs Frequ ency

42(c) S ign a l Input of inve rter 03

1)442(d) S ignal oUlput of inverte r

(54 3 (a ) S ign al mput of lone decode r

fgt)4 3 ()) S ign al of ca pac itor timin g

6r43(c) S ignal of resistor tim ing

Uh43 (c) S ign al [ter through 2 K res is to r

(I4 3 (e) S ig11 a l after throu gh 2 2 K resisto r

h7 Signal after thro ugh 27 K res is tor 43(f)

(g43(g) Outp u t of tone decod er

6944 I(a) Inpu t (+) of ampli fie r

4 4 lib) In pu t ( ) of ampli fi er I))

44 I (e) Ou tput Sign al of a mplifie r 70

70 44 fel) VolLage source of amplifi er

4 5 Sys te m ou tput s ignal 7

List Of Tables

Table Dcscript Ion

9Frequency band21

12 22 1 Types of Baseband Signal

253 Requirement fo r two or mUltipoint 46

254 Requirem ent for two or multJ point for

47Envelope del ay distortion

Chapter 1

Introduction of Powered Intercom Project

Introduction

A vast n e twork telecommunicatIOn llllks spans tltc in duS Trilaquolt zcd

COU ntne of the world carrymg telephone te legraph tclcvi ion n e5

p h ologra phs a nd ra dio programs ThIS n e twork IS con stro n llv heing

exp a nded a nd n ew invention s are increasin g its capaCIty ltIt breathtnllt lI1g

ra te The re were m any proble ms we have en cou ntered in th e bq~i l I inf( bu t

s lowly soluti on s have been found We have learn ed to li se the IlI1 llts m o re

e ffi c ie ntly a nd th e cos ts have dropped dramatIc a lly Nowodays there ltIre

m a n y typ es of links that has been use d to com mUI1lCCllr an ti Ilslng the

power su pply to co mmunicate is a new method

Inter com technology has been found 111 ea rlv 1 9~) Os ami s lowl It s

b een expanded to be used in local area network nor WIde lea network

Powered inter com is a new technology where It is slmi l r to lIinkss

intercom However wlreless lntercom IS a system there ~() Ineo n e C(Ul

communicate w1th each other 111 the same small a r ea (h ousr n bllil cll llg)

without using wire d links but for powered intcrcnm SOIneon e ju s t need to

plu g it to th e power supply without worryll1g on h ow to lin k the Inl r](om

By u s ing thi s techno logy it is more con venien t for the c u stomer tu put the

in tercom system s w ith ou t worrym g how to Ill s t ltl ll (mess) w lr(d) and n1lll(

o rganized Neve rtheless a lot o f problems to imple m ent this 1lt11lc o f

sys te m s

For th IS thesis the c haracteris tics on th~ powtrn ml errC)m ~11 1 hI

s tudied befo re Implement the product Neve rth eless thi S repo rt is Iso

s tudy case all the advan ced of telecommuI1Ication s

Chapter 2

Literature Review of Powered Intercom Project

21 WHAT IS COMMUNICATION

211 THE BLOCK DIAGRAM OF A COMMUNICATION SYSTEM

Fi gure 20 shows a cOllullonly used model Il) 1 Cl l l ll 1l l J11 iCl li u ll sy --lun

-l lhough it - lIggcsls a system -or cOllllllunicaLion be1ccn t u ICllhdCh InL~I(t d

or sonar In I hich Ihe system input and output 111 1 be localed 11 Ihe 11e ie

Regardless of the particular application and conli gu-iln II 11l1l1 lmli

trallsmission systems invariably involve three lllZljor sUbSYS tlll l ~~ 11l1bIl1lIloCl Ihl

channeL and d receiver In this literature review we II I lI s lul l bmiddot I h lllkill ~ t11 LLrI1l S

01 systems ror transk r of inforlllation between rcmolch IIK ll ed poi nls II is

limited to such systellls

mes sage message

sgnat

Inp~Jt

transducer T fansmlU8r

carner

Iransmll signal

R8C81ver

addl11ve nOise Interfereflce dls tNtlon res lJolllng from ba~d limlitl119 and non Ilns-cHllls S

c u lpu t ~IJnal

OIJIPll t jrr1sJu cer

Fig 2 I Block d iagram of a communic8 tion sys lcm (Rl fc 10 Re k l llU IIII

2111 Input Transducer

The vide vanety of possible sources of informatlOn refmiddota lll S III ffi JIlV (11 1 h 1r11 1

[arms [or mess a pes Regardless of their exa c t form hOW (lr IncSS rq~~e s 1Tl1 ~

be categorized as analog or digliol The former tTl) be 1ll 1l(lt-lt- cJ s fU Il CIIlt1I 1S

of a continu ous-time variable ([or example press u re t ll n pcrdl lll4 spLrch

mus iC l whereas the latter consist of discrete symbols (for rX d rnpk 1 nlt tl

text) Almost lIwanably the message produced by a sOll rce mbl be

converted bv a transducer to a for m SUItable for til c p ltrti cul r I pe f

cnrn mU111Calion system employed For CX2lillplc 111 elre t riri11

com tT1urlicarions speech waves are converted b cl nllCiUphullf Lo nll ~e

variatIons Sucl a converted 11leSsage is referred to as 111( Incssnrlf siqnu

In thi s book therefore a signal can be Interpreted as the tmiddotu idtin l1 01 a

qua n tIty often a vOlt2gC or current with ti me

2112 Transmitter

The purpose of the transmitter is to couple the mc~sI1~ Lo Llw ~ (Inll c l

Altho ugh it is not uncommon to find the input transd u ce l dll l c lv u lu plcc1

to the trans111ission medium as for example in some interLonl s stC1l1~ iL is

often nccessary to modulate a carrier wave With the s lgn 1 flillTI tile 1111111

transducer Modulation is the systematic vanation 0 1 some illlni) u ll o f Ill

carrier such as amplitude) phase or frequency in alc nrd d l1Ce 1111

function of th e n1essage slgnal There are several reasons f(gt r 11 ing (~rncr

and modulating it Important ones are (l l for ease of ra ci lduo n 1 10 red u ce

noise and interference (3) for channel assignment (4 ) for m Ultiplex ing or

transmlssion of several messages over a single chnnnc1 ln cl (5 I f J U VL rCO ITI l

equipment limitations Several of these reasons are scJf-explanHory Olhns

such as the second ill become more mcaningfui later

In additIOn to modulation other primary functions performed by the

transmi tter a r c fil tering amplillcation and coup ling th e moct u[ed s ipnaJ tu

the channel Ifor example through an antenna or o th e r 1 pprl1 pr JIC c ( ICT I

4

PIIlt1II Ihidmftl lJaklumul H~drlUil Unl c r Sl ll Nl 1aV S1lt1 S arn~n k UNIVEllt~nl MILnSr ~~ w

2 11 3 Channel

Tl w channel can have m any different for m s the most [amil iaL pc-h p is

rh e channel that exists between tlI e transmittin g an ten n a nl ) c OlTImLrLlnl

radio s tat ion and the receivIng antenna of a rad i() 111 thi 5 ch ~ nIH1 the

transmitted slgn al propagates through the 8 trn ospllfr e Dr fn e s Pju rr t il e

receli1ng antenna Hoovever it is not uncommon to Jlnd lhl~ trlnnlI1lcr

hard-wired to the receiver as in most local te lephone syste m s Th S -hlnnl

is vastly differen t from the radio example However ~ I ~ htnncls hC1H )lIe

th ing in common the signal undergoes d egradation fn ln lld I1 S ll11 tr f 1 I

receiver Although this degradatIOn may occur at ~m POlllt or 1I

communication system block diagram lt is customan iy i1 S S~t( l ~ llC d t th lil t

channe1 alone This degrad a tion often results from nOl sc rll rl qhr r lin(lt-

on-ed signals or lIlterference but also may lIlclude o lh er (hSLO I UOll cllcLh 1S

Nell such as fad lng signallcvels multiple transIniss io n P ill-h s 8nd fillr nnf

More about these unwanted perturbatIOns will be pr esented llo lll v

2114 Receiver

The receivers fu n ction is to extract the desIred messag( lrofll Imiddothe ITr-I~ I f d

signal at the ch ill1nel output and to convert It to fUI In Sl lltlhle f lll lit

output transducer Although amplification rn3 be 11IIC or ti ll IIfb l Il

atlons per[onned by the receiver especially in radio ( ()TIl11l1nllal J1) I1 ~ ) wh(n

lhe recelved Si gn al m ay be extremely weak the rn __ ~ i ll Junc lio n uf dH r L l l I C i

is to demodula ie the received signal Oft en It IS d es ire d th lI rcCCIIl rl( output be a scaled possibly delayed version of th e mcssd gc s iYIrI I I h e

modli lator mput although in some cases a morc ge n creo l rnnclo ll I Ih e

input rnessage is desired However as a result of the p re s cll (c or nO ise d nd

distortion tlus operatIOn is less than ldeal Ways of ~pprn ] hillg Illl k11

5

case of perfec t recovery wi ll be discussed as we p roceed

211 5 Output Transducer

The outpu t transdu cer completes the communicatIOn svstem This knee

converts th e el~Ll ic s Ignal at its in pu t InLO t he f rm c1csll(d hv I he svsIt m

u ser Perh aps the m os t common OUlput tran sdu cer IS 1Iucl spIkcr

However the re ar e many oth er examples s u ch as tltlpe rccorckrs pers0I w]

computers meters and cath ode-r ay tubes an d etc

212 CHANNEL CHARACTERISTICS

Noise Sources

No ise in a co mmunica tion sys tem can be cl lsslficcl Jt1 to two 1-1 lt1

categori es depend ing on its source Noise generated bv compone nt w it hll1

a co mmunication system s u ch as resis tors eicclron lubes ii nel sol U-llI(

acti ve devices is referr ed to as internal nOise The second ca tc~nr p~l( rnal

noise r esults from sources out s ide a commul11cation system 1IIclLllthr

a tmospheri c man -m a de and extrate rrestrial sou rces

Atmospheri c noise results primarily fro m SP Uri O U S )dl n wmTS

gen erated by the n a tural e lec trical d ischarges wit llll the t111uraquoph ltl

a ssocia ted with thunderstorms It is commonly rcfc rrrd to rl S 1)11( or

spitcncs Below about 100 MHz th e fi e ld s trcl12th of such radw 1 o- S IS

in ve rsely propo rtio na l to frequen cy Almosph en c II IHSC IS Lh Ii ln IZf d 011

the time do m ai n by largeamplitude s ho rt-dura tion bu rs ls lild IS nne of t illt

p rime examples o f n oise refe rred to as trl)I)[il~I(~ RecltlIlgte of llq i The

6

dependence on frequency atmospheric nOIse 8ffcrs ( CllllnWrCIltl1 A) l

broadcast radio which occupies the frequency ra n flc fm m 550 kfl lO 110

IIHiz m ore lh an it affects television and FM rd riio wlliill 11eldle in

lreq uency bands above 50 Mhz

i1a n - l11ade noise sources include high-voltage po( rl1 n ( corona dlS shy

charge COilllllUla to r-generated nOISE In electrica l lnotors aliturT10hik d

aircran 19ni t ion nOlse and switching-gear 1l00se Ign H lon n01~e (Hid

sWltching noise like atmospheric nOIse are Imru ls ivc in c Wfa uel lmpuhc

noise is Ih e predominant type of nOIse In switched vrc ll ne c hl lllwls gt11111

as lc1cphone channels For applicatlOlls such as Olee I rdJLsnli~si o I

Imp ulse noise is only an irritation factor hovrever It can 1)( ) s~ t J(Hl~

source of error in appilC3tIons involvIng transmIssion of cl lgnal el ata

Yet another importClrlL source of man -- Tn a de noist is LHlio- fr_~ qucncy

transmitters other than the one of Interest NUJSC Ju c to 1t1lcr tc nng

transmItters is commonly referred to as radlO-freq ll l1 cy in I e reTlllC( WFII

RFI IS p anicularly troublesome In SItuations 111 ~hICh i1 I ClC IIIIL dn tcllll ll IS

su bj ect to a high -density tran smitter environrrlen L -1 S Jn rnohdc

connn unications in a large city

Extraterrestrial noise sources include oLir sun and r)t l H~r ho t

heaven lv bodIes such as stars Owing to its high t Clllpcr)tlllT (tlfill(j C) md

rebliey close proximity to the earth the sun is an Intense bUI [UIIUllattiV

localized source of radio energy that extends ovcr a broad rrr-jl1lnry

spectrum Sim ilarly the stars are sources of wlde- iJalld rClth ~ntT0middot

Although m uch more distant and hence less ink n s e Ih lI1 t i l S II Il

7

nevertheless thev are collectively an importan t source o r n Oi s e IJCT 1 1 ~( n[

their vast numbers Radio stars such as quasars ltl nci p u lsm tgt t ~lbo

In l fnSe sources u f radio energy Considered a Sig ll Zll 5r1L1n c h v n~c1ln

astrCllt Omers such stars are vieved as anolher nlnSl oour( c bv

com nlun lc atlOlls l n gIneers The frequency f clngc or ~ oln r lind ( i JSIIlI C r1l)t~ C

exlends [rom a [evil megahertz to a fevv g igltlh e r t7 - 110Ih( 1 SOU l CC 01

Interference In communication systems is m u ltiple l r d ll s m ic clt)ll pt th s

These can resull from reflection off b u il d in gs th e (]rlh rp ln IK S lJleI

ShIpS or [rom refraclion by stratifications In the lranS ITlI S lt lnn Il t dlllln If

the scattering mechanism results in numerous [(fleeted (umpH1cnls be

received multipatb signal is noiselike and is ter m ed (l i(i 5e If lil e ITlUIUI l h

slgnal componen t IS composed of only one or tVO s lTnng 11 l tT tmiddotd fnv s 11 i ~

termed specular Finally signal degradatlOl1 In a corntn LtJl1 CiJ t0l1 ~ middot ~Ll nl C 1l1

occur because of random changes in attenuallOn w ilh lll 1 h e lril llSTn is SH11l

medium Such signal perturbations (disturbances) are rde n-cd Ln CiS Ji ) )

altbou g h it should be noted that specular m u itlp 1[h abo rcs llits III l l1 rlil1 ~

due to th e constructive and destructive interferen ce uf the Fltlird IIllllLlpk

signals

Typical usesFrequency Name Microwave Band (GHz)Band

Lon rnnsc n [11gnllon snnn r3 -30k l-l z c ry low frequency

Nai gatlonai 81tb rl(ilu30-300kHz Low frequen cy

IMm l imt nl liJo cli~ t I J S~ ilL Cmiddot1 11lJ1g cliree tlJ )1l flllcling COltlsl (jlla rd (( 111 111 lPnlIHLnlal IM rltIi S c IILIl m Ic c lc

nircrnfL Cllnl il l it ll

300-3000 Medium frequ en cy

ships telcgrmiddotp il tr lepllnne anu facsimd e ~llJp- flt- C iJ ~ t

3 - 30~ll-Iz High frequen cy (I-IF

VHF t eleJ~ioJl ( lhlnnltl 5 11 radio land lrdllltpOrlllinn

30-300 Very high frequency

private GHl c raft (tll t raffic cont rol laxi C Ilgt policr navlga noTlftl ltli ds

UHF tc IILgt n l hJIllll is raclto ~() n d( 11 1 I iris

03-3 Gl-lz Ultrahigh frequency 05- 10

suncd lI1lt( r ld r sw l i ite comm 1a dio ltiml le rs

20-30 30-40 40-6 0

10-2 0

s aleii lC lIlI1 lll Jldi~ alillh lc r 1l1l Cn)~1 illk~

Superhigh freq uency 60-80 3-30GI-lL

80- 100 airborn e rlc1 ar ltlpp rnarh radar middottotile r rdciar com m on

10- 124 citrrier Inn d m ollc 30-311lt] Extremel y hig h timiddotcq Rlilroad sen icc rOldOlr Iltlding

800-40 000 Infrared (80- 400) 10Hz) ~m

40k-75k Vis ible light (40-80) ~ tn Optl c01I C() llll JlL1 n11 ti (n~

GHz S vs tCln 75000- 1O~ 1 Ultrav iolet ligh t (12-40 ~ I r

G lIz wt1lltlcnq thj

Table 22 Frequ e ncy Bands With TypIcal Uses ([dc I to Reference II))

9

In ternal nOIse resu lts from th e random motIO n o f charge ca rri- in

e lect roni c com ponen ts It can be of two general types Iderrcd to s thermal

n(js e ca u sed by the random motion of free dcc rons In crmri u or or

SClnlCO n u c tor ~xci ted by th erm al agitation and shot 110 ~dtl cd by th e

runcom arrl aJ or discre te charge carriers 111 sllrh c1e lc( as lhen rllnnLc

tubes and semicondu ctor junc tion dev ices

2 2 Baseband signal types

We a re cons idering th e s ignals only a fter they have bCI OIne ek tnmiddott 1

s Igna ls s ta rt off in non-e lectncal fo rm (eg VOIce t-m per Itun) htlt 11(

been co nve rted to vo ltage u s ing some form o f tra n sdllce Ie g mluphollr middot

thermoeoll p ie)

These e lec trical sign als form the origina l Il1for lllttioll Illch i~ 10 he middot Ilt

the baseband O nce obtai ned they III always flli Il1 ln nc 01 two i)n)d

c la sses

221 Analogue signals

In these Ihe electri cal s igna l s h ows a contmu ous vari lt1l1 Ol1 II I rtmr five r a

wide ra nge of m agni tu des Ofte n th s tim e vanatton s the e Ll h tt of

an original non-elec trical signaJ (eg au preSSlll ltI nc ( I t ~gf In

microphone) so that the two arc sa Id to be ana logou s IWllce he nme of

analogue s ignal

Digital signals

IhcOsc e lec tr ica l siglla ls consi~ ( o r d iscontinuuus pu bes (or di ~It1 elel CIIIla lll ill

duc bu ciJ ltJ ngi ng tbluptl y tiom one d igi t to the nex l I lte Ire ll SI Idl ) led

S i t~lla l s as in a ld c~ prinl e r The most common type is o f cU UJC hill~ll ( lIdinL Ih Il

Acknowledgement

First of a ll I would like to tban k to God fo r giVin g me the sl r~J1 h i lJ1d

a bility to comple te the report a nd project for a bout 2 cmcstcrs A lo t of

c hallenges and prob le ms have been encountered dU rin g Ih e resea rches a nd

implementation o f the project No t forgotte n my beloved fDmi l ~ fu r gi in c lhe

morale supports and e ncou rltlgement Without the m Il IS middotltIY rilllllul t lor 11K

to handle the s itu a tions I wou ld a lso like to express m y grn ltudc to tI( people

wh o a r e In volved in th e project e it her it is direct ly o r mdll n Ilv e ~r(C I tlly l iJne

who are n amed belowshy

0 Kad im S u a idi (Dean of Engineering)

Mr AI-Kh a lid Hj Othman (Lecturer a nd S upe rvisor)

En Wan Abu Bakar amp En Zakana (l ab Assistants)

Mo reover I wou ld a lso like to take this opportllnilv 10 Ih lnk lo th e

u ndergradu ate sch olar s tudents under Faculty o f Engil eel illl Imiddot-ho hn I rcd

the report an d gave good comm en ts Thank you

ABSTRACT

Powered In Llt com is one of the n ew techn ologies 111 r l~ (ntn munic] OJ)

sys tem It m eans that the intercom is usin g th e power suppl) for the medium

It is mo re s imilar to the wireless intercom wh e re th ere is 11 lt) n ec middotd of c ~ rr

cables or technical kil to link to the other inte rcoms PowfTcd inlCleom -1

transmit and receive th e data in bo th way but not ll the Sl lnc me il If

duplex) Powered intercom is SUItab le use for house a nd dbo nice where 11ll

distance between the intercom is about 1500 fee l The po-elcrlI11IC I(Om 11 J

channels which it can be a dded up to 8 ch ann el (most appropnll() FCT

ch a nne l can communicate with each oth er by chmgin f Illl dl ~l l1 lwl smiddot Ilc h

Thus i t is more re liable rather th a n the presen t in tercom here- there is onl

one (m aster) which can con tac t the o thers hile the re~1 ol lv rltccI e I he dJW

(multiplexe r system) For further details about lhe ffCl tl1res a pp lic rio n d(s

circuils a nd im plementation for the Powered inlercom ill be lu cil ell a ll dzed

and wi ll be di sc u ssed in th is report

-- --

ABSTRAK

_

Powered intercom adalah salah smu tekno logi wg l(f hal ll d ldm

sistem kOlTIllnikasi Dengan erti kata lalll ia men of(u nalcan Sl lmbtT k il(lgtltl

sebagal medium perantaraan La m enyerLtp a l dcnf~an in l t J(ol n t rlrl p I rl r

dim ana kabe l dan kebolehan tekmkal tidak dipcrlukan d ll) m pCIW Jlll buJl111

a nt ara in tercom dengan yang lain Powered inlercom bolch rncng h l l] r eLm

m cncri m a data te lapi tidak di daJam satu m asa (scparu h d uplex) 1T[(ci

inte rcom a m a t sesu a i untuk kegunaan di rllmah ulLl pejltJiJd l d im altl j II ilk

antara satu intercorn dengan yang lain ialah ki ra -kJra 1500 k ltJl i ra JU Jl

m empllnya i 3 salura n dimana ia bolh ditingka tka n sebanya k S salu rall (ami l

sesuai) Setiap salUl-an boleh menghublln gi anta ra s at Lt sami Llin des

m en ukarkan s ui sn ya Olch itu ia lebill berkesan b Ibcll1 ci IllR 1 11 [( s ed 1lt11

dimallCl h anya satu yang dapat men ghantar dla Unt lrl m d dll lll] l

selanjutnya m engenai ciri-ClIi aplikasi dan pCmaS8 I1~ltHl a ka n ~lthT-llgk an ltlgi

el i d a lam laporan in

IUltI hrdmRI ~hklurnal ~adtl1l1 11 tK 111 Ml ~ - AI 1_

Conte nt

Chapt e r 1 Introduction

11 Introduc tion 12 Objectives an d a im of the project

Cha pt e r 2 Lit e r a ture Review

2 1 2 1 2 12

2 2 2 21 22 2 22 3 22 4 225

23 2 3 1 232

24 24 2 4 2

2 5 25 1 252

26 26 1

Wha t is communication Block Diaf middotam C h an n el Charac te ristics

Baseba nd s ign al types An a logu ej Digi tal sIgn als Base band and tcrmmalogy Class ification of modula tion types Advantages modu lation Analogue modulation

Multiplexing Frequen cy Trans mitte r Autom o tic Frequency Control of FM gene ral()r

Frequen cy Modula ted Radio Receiver Genelmiddotal Compon ent Des ign

Di s to rti o n And Noise Delay Di sto rtion No ise

Sign a l to No ise Ra tio Baseba nd System s

Page

2

1(1

I I 14 14 14

16 20 )_

J 1 14

11 c7

4

32

Chapter 3 Schematic Design and Components

3 1 SchematJc Design Components and Block diagram

Chapter 4 Results and Analysis

4 1 Power Supply 2 C-MOS Digital inverter (CD 4069)

43 Tone Decode r (LM567) 44 Audio Amplifier (LM386)

45 Outpu t of th e system

Conclusion and Recommendations Chapter 5

511

59

(0 62

11 )

hll 71

7 2

List of Figures

Figure Description Page

2 1 Block d iagram of communi cation sys te m

22 0 Classes o f s ign al I I

22 1 Frequ ency Divis ion MuJti plex concept IIgt

222 Frequen cy Division Multi p lexing

(a ) FM (b)FDM (c) Baseband s pctrum lY

23 1 Basic FM Generato r 21

2 32 Im proved PM Generato r l

233 PM gen erator wilh AFC circu it 2 1

234 Block d iagram of Lim ite r r ~-

235 Diagram uf Preampli fier 26

2 36 Im provement of symmetric clippe r 27

2 3 7 Charac teri s tic of frequen cy to am pli tude H

2 38 The u se of double-tu ned circui t 30

bull 124 1 Block d iagram of domes tic recelver ~

242 Fosley Seeley Discrimina lo r 3Y

243 Diagra m of Quadrature de tec to r -to

2 4 4 Phase shift 4 1

245 Block d iagram of gtbase Locked loop 43

25 I Typicl l ifferentlal de lay H

252 Typical Amplitu de vs Frequency respon se 46

255 Probabili ty of Bit Erro r in

261 Baseband System 33

57Schem a ti c Design O [ Powered In te rcom3 0

- 1 3 1 1 Block diagram o[ in tercom system shy

4 1 0 (a ) Sch em a ti c power s upp ly

roIb) Physical -ollage regulator

6 4 1(a) Inpu t powe r s u p ply s ign a l

6 1 4 J (b) Outpu t s ignal

024 2(a ) Gate tra n s fer

142 ()) Power d iss ipa tion vs Frequ ency

42(c) S ign a l Input of inve rter 03

1)442(d) S ignal oUlput of inverte r

(54 3 (a ) S ign al mput of lone decode r

fgt)4 3 ()) S ign al of ca pac itor timin g

6r43(c) S ignal of resistor tim ing

Uh43 (c) S ign al [ter through 2 K res is to r

(I4 3 (e) S ig11 a l after throu gh 2 2 K resisto r

h7 Signal after thro ugh 27 K res is tor 43(f)

(g43(g) Outp u t of tone decod er

6944 I(a) Inpu t (+) of ampli fie r

4 4 lib) In pu t ( ) of ampli fi er I))

44 I (e) Ou tput Sign al of a mplifie r 70

70 44 fel) VolLage source of amplifi er

4 5 Sys te m ou tput s ignal 7

List Of Tables

Table Dcscript Ion

9Frequency band21

12 22 1 Types of Baseband Signal

253 Requirement fo r two or mUltipoint 46

254 Requirem ent for two or multJ point for

47Envelope del ay distortion

Chapter 1

Introduction of Powered Intercom Project

Introduction

A vast n e twork telecommunicatIOn llllks spans tltc in duS Trilaquolt zcd

COU ntne of the world carrymg telephone te legraph tclcvi ion n e5

p h ologra phs a nd ra dio programs ThIS n e twork IS con stro n llv heing

exp a nded a nd n ew invention s are increasin g its capaCIty ltIt breathtnllt lI1g

ra te The re were m any proble ms we have en cou ntered in th e bq~i l I inf( bu t

s lowly soluti on s have been found We have learn ed to li se the IlI1 llts m o re

e ffi c ie ntly a nd th e cos ts have dropped dramatIc a lly Nowodays there ltIre

m a n y typ es of links that has been use d to com mUI1lCCllr an ti Ilslng the

power su pply to co mmunicate is a new method

Inter com technology has been found 111 ea rlv 1 9~) Os ami s lowl It s

b een expanded to be used in local area network nor WIde lea network

Powered inter com is a new technology where It is slmi l r to lIinkss

intercom However wlreless lntercom IS a system there ~() Ineo n e C(Ul

communicate w1th each other 111 the same small a r ea (h ousr n bllil cll llg)

without using wire d links but for powered intcrcnm SOIneon e ju s t need to

plu g it to th e power supply without worryll1g on h ow to lin k the Inl r](om

By u s ing thi s techno logy it is more con venien t for the c u stomer tu put the

in tercom system s w ith ou t worrym g how to Ill s t ltl ll (mess) w lr(d) and n1lll(

o rganized Neve rtheless a lot o f problems to imple m ent this 1lt11lc o f

sys te m s

For th IS thesis the c haracteris tics on th~ powtrn ml errC)m ~11 1 hI

s tudied befo re Implement the product Neve rth eless thi S repo rt is Iso

s tudy case all the advan ced of telecommuI1Ication s

Chapter 2

Literature Review of Powered Intercom Project

21 WHAT IS COMMUNICATION

211 THE BLOCK DIAGRAM OF A COMMUNICATION SYSTEM

Fi gure 20 shows a cOllullonly used model Il) 1 Cl l l ll 1l l J11 iCl li u ll sy --lun

-l lhough it - lIggcsls a system -or cOllllllunicaLion be1ccn t u ICllhdCh InL~I(t d

or sonar In I hich Ihe system input and output 111 1 be localed 11 Ihe 11e ie

Regardless of the particular application and conli gu-iln II 11l1l1 lmli

trallsmission systems invariably involve three lllZljor sUbSYS tlll l ~~ 11l1bIl1lIloCl Ihl

channeL and d receiver In this literature review we II I lI s lul l bmiddot I h lllkill ~ t11 LLrI1l S

01 systems ror transk r of inforlllation between rcmolch IIK ll ed poi nls II is

limited to such systellls

mes sage message

sgnat

Inp~Jt

transducer T fansmlU8r

carner

Iransmll signal

R8C81ver

addl11ve nOise Interfereflce dls tNtlon res lJolllng from ba~d limlitl119 and non Ilns-cHllls S

c u lpu t ~IJnal

OIJIPll t jrr1sJu cer

Fig 2 I Block d iagram of a communic8 tion sys lcm (Rl fc 10 Re k l llU IIII

2111 Input Transducer

The vide vanety of possible sources of informatlOn refmiddota lll S III ffi JIlV (11 1 h 1r11 1

[arms [or mess a pes Regardless of their exa c t form hOW (lr IncSS rq~~e s 1Tl1 ~

be categorized as analog or digliol The former tTl) be 1ll 1l(lt-lt- cJ s fU Il CIIlt1I 1S

of a continu ous-time variable ([or example press u re t ll n pcrdl lll4 spLrch

mus iC l whereas the latter consist of discrete symbols (for rX d rnpk 1 nlt tl

text) Almost lIwanably the message produced by a sOll rce mbl be

converted bv a transducer to a for m SUItable for til c p ltrti cul r I pe f

cnrn mU111Calion system employed For CX2lillplc 111 elre t riri11

com tT1urlicarions speech waves are converted b cl nllCiUphullf Lo nll ~e

variatIons Sucl a converted 11leSsage is referred to as 111( Incssnrlf siqnu

In thi s book therefore a signal can be Interpreted as the tmiddotu idtin l1 01 a

qua n tIty often a vOlt2gC or current with ti me

2112 Transmitter

The purpose of the transmitter is to couple the mc~sI1~ Lo Llw ~ (Inll c l

Altho ugh it is not uncommon to find the input transd u ce l dll l c lv u lu plcc1

to the trans111ission medium as for example in some interLonl s stC1l1~ iL is

often nccessary to modulate a carrier wave With the s lgn 1 flillTI tile 1111111

transducer Modulation is the systematic vanation 0 1 some illlni) u ll o f Ill

carrier such as amplitude) phase or frequency in alc nrd d l1Ce 1111

function of th e n1essage slgnal There are several reasons f(gt r 11 ing (~rncr

and modulating it Important ones are (l l for ease of ra ci lduo n 1 10 red u ce

noise and interference (3) for channel assignment (4 ) for m Ultiplex ing or

transmlssion of several messages over a single chnnnc1 ln cl (5 I f J U VL rCO ITI l

equipment limitations Several of these reasons are scJf-explanHory Olhns

such as the second ill become more mcaningfui later

In additIOn to modulation other primary functions performed by the

transmi tter a r c fil tering amplillcation and coup ling th e moct u[ed s ipnaJ tu

the channel Ifor example through an antenna or o th e r 1 pprl1 pr JIC c ( ICT I

4

PIIlt1II Ihidmftl lJaklumul H~drlUil Unl c r Sl ll Nl 1aV S1lt1 S arn~n k UNIVEllt~nl MILnSr ~~ w

2 11 3 Channel

Tl w channel can have m any different for m s the most [amil iaL pc-h p is

rh e channel that exists between tlI e transmittin g an ten n a nl ) c OlTImLrLlnl

radio s tat ion and the receivIng antenna of a rad i() 111 thi 5 ch ~ nIH1 the

transmitted slgn al propagates through the 8 trn ospllfr e Dr fn e s Pju rr t il e

receli1ng antenna Hoovever it is not uncommon to Jlnd lhl~ trlnnlI1lcr

hard-wired to the receiver as in most local te lephone syste m s Th S -hlnnl

is vastly differen t from the radio example However ~ I ~ htnncls hC1H )lIe

th ing in common the signal undergoes d egradation fn ln lld I1 S ll11 tr f 1 I

receiver Although this degradatIOn may occur at ~m POlllt or 1I

communication system block diagram lt is customan iy i1 S S~t( l ~ llC d t th lil t

channe1 alone This degrad a tion often results from nOl sc rll rl qhr r lin(lt-

on-ed signals or lIlterference but also may lIlclude o lh er (hSLO I UOll cllcLh 1S

Nell such as fad lng signallcvels multiple transIniss io n P ill-h s 8nd fillr nnf

More about these unwanted perturbatIOns will be pr esented llo lll v

2114 Receiver

The receivers fu n ction is to extract the desIred messag( lrofll Imiddothe ITr-I~ I f d

signal at the ch ill1nel output and to convert It to fUI In Sl lltlhle f lll lit

output transducer Although amplification rn3 be 11IIC or ti ll IIfb l Il

atlons per[onned by the receiver especially in radio ( ()TIl11l1nllal J1) I1 ~ ) wh(n

lhe recelved Si gn al m ay be extremely weak the rn __ ~ i ll Junc lio n uf dH r L l l I C i

is to demodula ie the received signal Oft en It IS d es ire d th lI rcCCIIl rl( output be a scaled possibly delayed version of th e mcssd gc s iYIrI I I h e

modli lator mput although in some cases a morc ge n creo l rnnclo ll I Ih e

input rnessage is desired However as a result of the p re s cll (c or nO ise d nd

distortion tlus operatIOn is less than ldeal Ways of ~pprn ] hillg Illl k11

5

case of perfec t recovery wi ll be discussed as we p roceed

211 5 Output Transducer

The outpu t transdu cer completes the communicatIOn svstem This knee

converts th e el~Ll ic s Ignal at its in pu t InLO t he f rm c1csll(d hv I he svsIt m

u ser Perh aps the m os t common OUlput tran sdu cer IS 1Iucl spIkcr

However the re ar e many oth er examples s u ch as tltlpe rccorckrs pers0I w]

computers meters and cath ode-r ay tubes an d etc

212 CHANNEL CHARACTERISTICS

Noise Sources

No ise in a co mmunica tion sys tem can be cl lsslficcl Jt1 to two 1-1 lt1

categori es depend ing on its source Noise generated bv compone nt w it hll1

a co mmunication system s u ch as resis tors eicclron lubes ii nel sol U-llI(

acti ve devices is referr ed to as internal nOise The second ca tc~nr p~l( rnal

noise r esults from sources out s ide a commul11cation system 1IIclLllthr

a tmospheri c man -m a de and extrate rrestrial sou rces

Atmospheri c noise results primarily fro m SP Uri O U S )dl n wmTS

gen erated by the n a tural e lec trical d ischarges wit llll the t111uraquoph ltl

a ssocia ted with thunderstorms It is commonly rcfc rrrd to rl S 1)11( or

spitcncs Below about 100 MHz th e fi e ld s trcl12th of such radw 1 o- S IS

in ve rsely propo rtio na l to frequen cy Almosph en c II IHSC IS Lh Ii ln IZf d 011

the time do m ai n by largeamplitude s ho rt-dura tion bu rs ls lild IS nne of t illt

p rime examples o f n oise refe rred to as trl)I)[il~I(~ RecltlIlgte of llq i The

6

dependence on frequency atmospheric nOIse 8ffcrs ( CllllnWrCIltl1 A) l

broadcast radio which occupies the frequency ra n flc fm m 550 kfl lO 110

IIHiz m ore lh an it affects television and FM rd riio wlliill 11eldle in

lreq uency bands above 50 Mhz

i1a n - l11ade noise sources include high-voltage po( rl1 n ( corona dlS shy

charge COilllllUla to r-generated nOISE In electrica l lnotors aliturT10hik d

aircran 19ni t ion nOlse and switching-gear 1l00se Ign H lon n01~e (Hid

sWltching noise like atmospheric nOIse are Imru ls ivc in c Wfa uel lmpuhc

noise is Ih e predominant type of nOIse In switched vrc ll ne c hl lllwls gt11111

as lc1cphone channels For applicatlOlls such as Olee I rdJLsnli~si o I

Imp ulse noise is only an irritation factor hovrever It can 1)( ) s~ t J(Hl~

source of error in appilC3tIons involvIng transmIssion of cl lgnal el ata

Yet another importClrlL source of man -- Tn a de noist is LHlio- fr_~ qucncy

transmitters other than the one of Interest NUJSC Ju c to 1t1lcr tc nng

transmItters is commonly referred to as radlO-freq ll l1 cy in I e reTlllC( WFII

RFI IS p anicularly troublesome In SItuations 111 ~hICh i1 I ClC IIIIL dn tcllll ll IS

su bj ect to a high -density tran smitter environrrlen L -1 S Jn rnohdc

connn unications in a large city

Extraterrestrial noise sources include oLir sun and r)t l H~r ho t

heaven lv bodIes such as stars Owing to its high t Clllpcr)tlllT (tlfill(j C) md

rebliey close proximity to the earth the sun is an Intense bUI [UIIUllattiV

localized source of radio energy that extends ovcr a broad rrr-jl1lnry

spectrum Sim ilarly the stars are sources of wlde- iJalld rClth ~ntT0middot

Although m uch more distant and hence less ink n s e Ih lI1 t i l S II Il

7

nevertheless thev are collectively an importan t source o r n Oi s e IJCT 1 1 ~( n[

their vast numbers Radio stars such as quasars ltl nci p u lsm tgt t ~lbo

In l fnSe sources u f radio energy Considered a Sig ll Zll 5r1L1n c h v n~c1ln

astrCllt Omers such stars are vieved as anolher nlnSl oour( c bv

com nlun lc atlOlls l n gIneers The frequency f clngc or ~ oln r lind ( i JSIIlI C r1l)t~ C

exlends [rom a [evil megahertz to a fevv g igltlh e r t7 - 110Ih( 1 SOU l CC 01

Interference In communication systems is m u ltiple l r d ll s m ic clt)ll pt th s

These can resull from reflection off b u il d in gs th e (]rlh rp ln IK S lJleI

ShIpS or [rom refraclion by stratifications In the lranS ITlI S lt lnn Il t dlllln If

the scattering mechanism results in numerous [(fleeted (umpH1cnls be

received multipatb signal is noiselike and is ter m ed (l i(i 5e If lil e ITlUIUI l h

slgnal componen t IS composed of only one or tVO s lTnng 11 l tT tmiddotd fnv s 11 i ~

termed specular Finally signal degradatlOl1 In a corntn LtJl1 CiJ t0l1 ~ middot ~Ll nl C 1l1

occur because of random changes in attenuallOn w ilh lll 1 h e lril llSTn is SH11l

medium Such signal perturbations (disturbances) are rde n-cd Ln CiS Ji ) )

altbou g h it should be noted that specular m u itlp 1[h abo rcs llits III l l1 rlil1 ~

due to th e constructive and destructive interferen ce uf the Fltlird IIllllLlpk

signals

Typical usesFrequency Name Microwave Band (GHz)Band

Lon rnnsc n [11gnllon snnn r3 -30k l-l z c ry low frequency

Nai gatlonai 81tb rl(ilu30-300kHz Low frequen cy

IMm l imt nl liJo cli~ t I J S~ ilL Cmiddot1 11lJ1g cliree tlJ )1l flllcling COltlsl (jlla rd (( 111 111 lPnlIHLnlal IM rltIi S c IILIl m Ic c lc

nircrnfL Cllnl il l it ll

300-3000 Medium frequ en cy

ships telcgrmiddotp il tr lepllnne anu facsimd e ~llJp- flt- C iJ ~ t

3 - 30~ll-Iz High frequen cy (I-IF

VHF t eleJ~ioJl ( lhlnnltl 5 11 radio land lrdllltpOrlllinn

30-300 Very high frequency

private GHl c raft (tll t raffic cont rol laxi C Ilgt policr navlga noTlftl ltli ds

UHF tc IILgt n l hJIllll is raclto ~() n d( 11 1 I iris

03-3 Gl-lz Ultrahigh frequency 05- 10

suncd lI1lt( r ld r sw l i ite comm 1a dio ltiml le rs

20-30 30-40 40-6 0

10-2 0

s aleii lC lIlI1 lll Jldi~ alillh lc r 1l1l Cn)~1 illk~

Superhigh freq uency 60-80 3-30GI-lL

80- 100 airborn e rlc1 ar ltlpp rnarh radar middottotile r rdciar com m on

10- 124 citrrier Inn d m ollc 30-311lt] Extremel y hig h timiddotcq Rlilroad sen icc rOldOlr Iltlding

800-40 000 Infrared (80- 400) 10Hz) ~m

40k-75k Vis ible light (40-80) ~ tn Optl c01I C() llll JlL1 n11 ti (n~

GHz S vs tCln 75000- 1O~ 1 Ultrav iolet ligh t (12-40 ~ I r

G lIz wt1lltlcnq thj

Table 22 Frequ e ncy Bands With TypIcal Uses ([dc I to Reference II))

9

In ternal nOIse resu lts from th e random motIO n o f charge ca rri- in

e lect roni c com ponen ts It can be of two general types Iderrcd to s thermal

n(js e ca u sed by the random motion of free dcc rons In crmri u or or

SClnlCO n u c tor ~xci ted by th erm al agitation and shot 110 ~dtl cd by th e

runcom arrl aJ or discre te charge carriers 111 sllrh c1e lc( as lhen rllnnLc

tubes and semicondu ctor junc tion dev ices

2 2 Baseband signal types

We a re cons idering th e s ignals only a fter they have bCI OIne ek tnmiddott 1

s Igna ls s ta rt off in non-e lectncal fo rm (eg VOIce t-m per Itun) htlt 11(

been co nve rted to vo ltage u s ing some form o f tra n sdllce Ie g mluphollr middot

thermoeoll p ie)

These e lec trical sign als form the origina l Il1for lllttioll Illch i~ 10 he middot Ilt

the baseband O nce obtai ned they III always flli Il1 ln nc 01 two i)n)d

c la sses

221 Analogue signals

In these Ihe electri cal s igna l s h ows a contmu ous vari lt1l1 Ol1 II I rtmr five r a

wide ra nge of m agni tu des Ofte n th s tim e vanatton s the e Ll h tt of

an original non-elec trical signaJ (eg au preSSlll ltI nc ( I t ~gf In

microphone) so that the two arc sa Id to be ana logou s IWllce he nme of

analogue s ignal

Digital signals

IhcOsc e lec tr ica l siglla ls consi~ ( o r d iscontinuuus pu bes (or di ~It1 elel CIIIla lll ill

duc bu ciJ ltJ ngi ng tbluptl y tiom one d igi t to the nex l I lte Ire ll SI Idl ) led

S i t~lla l s as in a ld c~ prinl e r The most common type is o f cU UJC hill~ll ( lIdinL Ih Il

ABSTRACT

Powered In Llt com is one of the n ew techn ologies 111 r l~ (ntn munic] OJ)

sys tem It m eans that the intercom is usin g th e power suppl) for the medium

It is mo re s imilar to the wireless intercom wh e re th ere is 11 lt) n ec middotd of c ~ rr

cables or technical kil to link to the other inte rcoms PowfTcd inlCleom -1

transmit and receive th e data in bo th way but not ll the Sl lnc me il If

duplex) Powered intercom is SUItab le use for house a nd dbo nice where 11ll

distance between the intercom is about 1500 fee l The po-elcrlI11IC I(Om 11 J

channels which it can be a dded up to 8 ch ann el (most appropnll() FCT

ch a nne l can communicate with each oth er by chmgin f Illl dl ~l l1 lwl smiddot Ilc h

Thus i t is more re liable rather th a n the presen t in tercom here- there is onl

one (m aster) which can con tac t the o thers hile the re~1 ol lv rltccI e I he dJW

(multiplexe r system) For further details about lhe ffCl tl1res a pp lic rio n d(s

circuils a nd im plementation for the Powered inlercom ill be lu cil ell a ll dzed

and wi ll be di sc u ssed in th is report

-- --

ABSTRAK

_

Powered intercom adalah salah smu tekno logi wg l(f hal ll d ldm

sistem kOlTIllnikasi Dengan erti kata lalll ia men of(u nalcan Sl lmbtT k il(lgtltl

sebagal medium perantaraan La m enyerLtp a l dcnf~an in l t J(ol n t rlrl p I rl r

dim ana kabe l dan kebolehan tekmkal tidak dipcrlukan d ll) m pCIW Jlll buJl111

a nt ara in tercom dengan yang lain Powered inlercom bolch rncng h l l] r eLm

m cncri m a data te lapi tidak di daJam satu m asa (scparu h d uplex) 1T[(ci

inte rcom a m a t sesu a i untuk kegunaan di rllmah ulLl pejltJiJd l d im altl j II ilk

antara satu intercorn dengan yang lain ialah ki ra -kJra 1500 k ltJl i ra JU Jl

m empllnya i 3 salura n dimana ia bolh ditingka tka n sebanya k S salu rall (ami l

sesuai) Setiap salUl-an boleh menghublln gi anta ra s at Lt sami Llin des

m en ukarkan s ui sn ya Olch itu ia lebill berkesan b Ibcll1 ci IllR 1 11 [( s ed 1lt11

dimallCl h anya satu yang dapat men ghantar dla Unt lrl m d dll lll] l

selanjutnya m engenai ciri-ClIi aplikasi dan pCmaS8 I1~ltHl a ka n ~lthT-llgk an ltlgi

el i d a lam laporan in

IUltI hrdmRI ~hklurnal ~adtl1l1 11 tK 111 Ml ~ - AI 1_

Conte nt

Chapt e r 1 Introduction

11 Introduc tion 12 Objectives an d a im of the project

Cha pt e r 2 Lit e r a ture Review

2 1 2 1 2 12

2 2 2 21 22 2 22 3 22 4 225

23 2 3 1 232

24 24 2 4 2

2 5 25 1 252

26 26 1

Wha t is communication Block Diaf middotam C h an n el Charac te ristics

Baseba nd s ign al types An a logu ej Digi tal sIgn als Base band and tcrmmalogy Class ification of modula tion types Advantages modu lation Analogue modulation

Multiplexing Frequen cy Trans mitte r Autom o tic Frequency Control of FM gene ral()r

Frequen cy Modula ted Radio Receiver Genelmiddotal Compon ent Des ign

Di s to rti o n And Noise Delay Di sto rtion No ise

Sign a l to No ise Ra tio Baseba nd System s

Page

2

1(1

I I 14 14 14

16 20 )_

J 1 14

11 c7

4

32

Chapter 3 Schematic Design and Components

3 1 SchematJc Design Components and Block diagram

Chapter 4 Results and Analysis

4 1 Power Supply 2 C-MOS Digital inverter (CD 4069)

43 Tone Decode r (LM567) 44 Audio Amplifier (LM386)

45 Outpu t of th e system

Conclusion and Recommendations Chapter 5

511

59

(0 62

11 )

hll 71

7 2

List of Figures

Figure Description Page

2 1 Block d iagram of communi cation sys te m

22 0 Classes o f s ign al I I

22 1 Frequ ency Divis ion MuJti plex concept IIgt

222 Frequen cy Division Multi p lexing

(a ) FM (b)FDM (c) Baseband s pctrum lY

23 1 Basic FM Generato r 21

2 32 Im proved PM Generato r l

233 PM gen erator wilh AFC circu it 2 1

234 Block d iagram of Lim ite r r ~-

235 Diagram uf Preampli fier 26

2 36 Im provement of symmetric clippe r 27

2 3 7 Charac teri s tic of frequen cy to am pli tude H

2 38 The u se of double-tu ned circui t 30

bull 124 1 Block d iagram of domes tic recelver ~

242 Fosley Seeley Discrimina lo r 3Y

243 Diagra m of Quadrature de tec to r -to

2 4 4 Phase shift 4 1

245 Block d iagram of gtbase Locked loop 43

25 I Typicl l ifferentlal de lay H

252 Typical Amplitu de vs Frequency respon se 46

255 Probabili ty of Bit Erro r in

261 Baseband System 33

57Schem a ti c Design O [ Powered In te rcom3 0

- 1 3 1 1 Block diagram o[ in tercom system shy

4 1 0 (a ) Sch em a ti c power s upp ly

roIb) Physical -ollage regulator

6 4 1(a) Inpu t powe r s u p ply s ign a l

6 1 4 J (b) Outpu t s ignal

024 2(a ) Gate tra n s fer

142 ()) Power d iss ipa tion vs Frequ ency

42(c) S ign a l Input of inve rter 03

1)442(d) S ignal oUlput of inverte r

(54 3 (a ) S ign al mput of lone decode r

fgt)4 3 ()) S ign al of ca pac itor timin g

6r43(c) S ignal of resistor tim ing

Uh43 (c) S ign al [ter through 2 K res is to r

(I4 3 (e) S ig11 a l after throu gh 2 2 K resisto r

h7 Signal after thro ugh 27 K res is tor 43(f)

(g43(g) Outp u t of tone decod er

6944 I(a) Inpu t (+) of ampli fie r

4 4 lib) In pu t ( ) of ampli fi er I))

44 I (e) Ou tput Sign al of a mplifie r 70

70 44 fel) VolLage source of amplifi er

4 5 Sys te m ou tput s ignal 7

List Of Tables

Table Dcscript Ion

9Frequency band21

12 22 1 Types of Baseband Signal

253 Requirement fo r two or mUltipoint 46

254 Requirem ent for two or multJ point for

47Envelope del ay distortion

Chapter 1

Introduction of Powered Intercom Project

Introduction

A vast n e twork telecommunicatIOn llllks spans tltc in duS Trilaquolt zcd

COU ntne of the world carrymg telephone te legraph tclcvi ion n e5

p h ologra phs a nd ra dio programs ThIS n e twork IS con stro n llv heing

exp a nded a nd n ew invention s are increasin g its capaCIty ltIt breathtnllt lI1g

ra te The re were m any proble ms we have en cou ntered in th e bq~i l I inf( bu t

s lowly soluti on s have been found We have learn ed to li se the IlI1 llts m o re

e ffi c ie ntly a nd th e cos ts have dropped dramatIc a lly Nowodays there ltIre

m a n y typ es of links that has been use d to com mUI1lCCllr an ti Ilslng the

power su pply to co mmunicate is a new method

Inter com technology has been found 111 ea rlv 1 9~) Os ami s lowl It s

b een expanded to be used in local area network nor WIde lea network

Powered inter com is a new technology where It is slmi l r to lIinkss

intercom However wlreless lntercom IS a system there ~() Ineo n e C(Ul

communicate w1th each other 111 the same small a r ea (h ousr n bllil cll llg)

without using wire d links but for powered intcrcnm SOIneon e ju s t need to

plu g it to th e power supply without worryll1g on h ow to lin k the Inl r](om

By u s ing thi s techno logy it is more con venien t for the c u stomer tu put the

in tercom system s w ith ou t worrym g how to Ill s t ltl ll (mess) w lr(d) and n1lll(

o rganized Neve rtheless a lot o f problems to imple m ent this 1lt11lc o f

sys te m s

For th IS thesis the c haracteris tics on th~ powtrn ml errC)m ~11 1 hI

s tudied befo re Implement the product Neve rth eless thi S repo rt is Iso

s tudy case all the advan ced of telecommuI1Ication s

Chapter 2

Literature Review of Powered Intercom Project

21 WHAT IS COMMUNICATION

211 THE BLOCK DIAGRAM OF A COMMUNICATION SYSTEM

Fi gure 20 shows a cOllullonly used model Il) 1 Cl l l ll 1l l J11 iCl li u ll sy --lun

-l lhough it - lIggcsls a system -or cOllllllunicaLion be1ccn t u ICllhdCh InL~I(t d

or sonar In I hich Ihe system input and output 111 1 be localed 11 Ihe 11e ie

Regardless of the particular application and conli gu-iln II 11l1l1 lmli

trallsmission systems invariably involve three lllZljor sUbSYS tlll l ~~ 11l1bIl1lIloCl Ihl

channeL and d receiver In this literature review we II I lI s lul l bmiddot I h lllkill ~ t11 LLrI1l S

01 systems ror transk r of inforlllation between rcmolch IIK ll ed poi nls II is

limited to such systellls

mes sage message

sgnat

Inp~Jt

transducer T fansmlU8r

carner

Iransmll signal

R8C81ver

addl11ve nOise Interfereflce dls tNtlon res lJolllng from ba~d limlitl119 and non Ilns-cHllls S

c u lpu t ~IJnal

OIJIPll t jrr1sJu cer

Fig 2 I Block d iagram of a communic8 tion sys lcm (Rl fc 10 Re k l llU IIII

2111 Input Transducer

The vide vanety of possible sources of informatlOn refmiddota lll S III ffi JIlV (11 1 h 1r11 1

[arms [or mess a pes Regardless of their exa c t form hOW (lr IncSS rq~~e s 1Tl1 ~

be categorized as analog or digliol The former tTl) be 1ll 1l(lt-lt- cJ s fU Il CIIlt1I 1S

of a continu ous-time variable ([or example press u re t ll n pcrdl lll4 spLrch

mus iC l whereas the latter consist of discrete symbols (for rX d rnpk 1 nlt tl

text) Almost lIwanably the message produced by a sOll rce mbl be

converted bv a transducer to a for m SUItable for til c p ltrti cul r I pe f

cnrn mU111Calion system employed For CX2lillplc 111 elre t riri11

com tT1urlicarions speech waves are converted b cl nllCiUphullf Lo nll ~e

variatIons Sucl a converted 11leSsage is referred to as 111( Incssnrlf siqnu

In thi s book therefore a signal can be Interpreted as the tmiddotu idtin l1 01 a

qua n tIty often a vOlt2gC or current with ti me

2112 Transmitter

The purpose of the transmitter is to couple the mc~sI1~ Lo Llw ~ (Inll c l

Altho ugh it is not uncommon to find the input transd u ce l dll l c lv u lu plcc1

to the trans111ission medium as for example in some interLonl s stC1l1~ iL is

often nccessary to modulate a carrier wave With the s lgn 1 flillTI tile 1111111

transducer Modulation is the systematic vanation 0 1 some illlni) u ll o f Ill

carrier such as amplitude) phase or frequency in alc nrd d l1Ce 1111

function of th e n1essage slgnal There are several reasons f(gt r 11 ing (~rncr

and modulating it Important ones are (l l for ease of ra ci lduo n 1 10 red u ce

noise and interference (3) for channel assignment (4 ) for m Ultiplex ing or

transmlssion of several messages over a single chnnnc1 ln cl (5 I f J U VL rCO ITI l

equipment limitations Several of these reasons are scJf-explanHory Olhns

such as the second ill become more mcaningfui later

In additIOn to modulation other primary functions performed by the

transmi tter a r c fil tering amplillcation and coup ling th e moct u[ed s ipnaJ tu

the channel Ifor example through an antenna or o th e r 1 pprl1 pr JIC c ( ICT I

4

PIIlt1II Ihidmftl lJaklumul H~drlUil Unl c r Sl ll Nl 1aV S1lt1 S arn~n k UNIVEllt~nl MILnSr ~~ w

2 11 3 Channel

Tl w channel can have m any different for m s the most [amil iaL pc-h p is

rh e channel that exists between tlI e transmittin g an ten n a nl ) c OlTImLrLlnl

radio s tat ion and the receivIng antenna of a rad i() 111 thi 5 ch ~ nIH1 the

transmitted slgn al propagates through the 8 trn ospllfr e Dr fn e s Pju rr t il e

receli1ng antenna Hoovever it is not uncommon to Jlnd lhl~ trlnnlI1lcr

hard-wired to the receiver as in most local te lephone syste m s Th S -hlnnl

is vastly differen t from the radio example However ~ I ~ htnncls hC1H )lIe

th ing in common the signal undergoes d egradation fn ln lld I1 S ll11 tr f 1 I

receiver Although this degradatIOn may occur at ~m POlllt or 1I

communication system block diagram lt is customan iy i1 S S~t( l ~ llC d t th lil t

channe1 alone This degrad a tion often results from nOl sc rll rl qhr r lin(lt-

on-ed signals or lIlterference but also may lIlclude o lh er (hSLO I UOll cllcLh 1S

Nell such as fad lng signallcvels multiple transIniss io n P ill-h s 8nd fillr nnf

More about these unwanted perturbatIOns will be pr esented llo lll v

2114 Receiver

The receivers fu n ction is to extract the desIred messag( lrofll Imiddothe ITr-I~ I f d

signal at the ch ill1nel output and to convert It to fUI In Sl lltlhle f lll lit

output transducer Although amplification rn3 be 11IIC or ti ll IIfb l Il

atlons per[onned by the receiver especially in radio ( ()TIl11l1nllal J1) I1 ~ ) wh(n

lhe recelved Si gn al m ay be extremely weak the rn __ ~ i ll Junc lio n uf dH r L l l I C i

is to demodula ie the received signal Oft en It IS d es ire d th lI rcCCIIl rl( output be a scaled possibly delayed version of th e mcssd gc s iYIrI I I h e

modli lator mput although in some cases a morc ge n creo l rnnclo ll I Ih e

input rnessage is desired However as a result of the p re s cll (c or nO ise d nd

distortion tlus operatIOn is less than ldeal Ways of ~pprn ] hillg Illl k11

5

case of perfec t recovery wi ll be discussed as we p roceed

211 5 Output Transducer

The outpu t transdu cer completes the communicatIOn svstem This knee

converts th e el~Ll ic s Ignal at its in pu t InLO t he f rm c1csll(d hv I he svsIt m

u ser Perh aps the m os t common OUlput tran sdu cer IS 1Iucl spIkcr

However the re ar e many oth er examples s u ch as tltlpe rccorckrs pers0I w]

computers meters and cath ode-r ay tubes an d etc

212 CHANNEL CHARACTERISTICS

Noise Sources

No ise in a co mmunica tion sys tem can be cl lsslficcl Jt1 to two 1-1 lt1

categori es depend ing on its source Noise generated bv compone nt w it hll1

a co mmunication system s u ch as resis tors eicclron lubes ii nel sol U-llI(

acti ve devices is referr ed to as internal nOise The second ca tc~nr p~l( rnal

noise r esults from sources out s ide a commul11cation system 1IIclLllthr

a tmospheri c man -m a de and extrate rrestrial sou rces

Atmospheri c noise results primarily fro m SP Uri O U S )dl n wmTS

gen erated by the n a tural e lec trical d ischarges wit llll the t111uraquoph ltl

a ssocia ted with thunderstorms It is commonly rcfc rrrd to rl S 1)11( or

spitcncs Below about 100 MHz th e fi e ld s trcl12th of such radw 1 o- S IS

in ve rsely propo rtio na l to frequen cy Almosph en c II IHSC IS Lh Ii ln IZf d 011

the time do m ai n by largeamplitude s ho rt-dura tion bu rs ls lild IS nne of t illt

p rime examples o f n oise refe rred to as trl)I)[il~I(~ RecltlIlgte of llq i The

6

dependence on frequency atmospheric nOIse 8ffcrs ( CllllnWrCIltl1 A) l

broadcast radio which occupies the frequency ra n flc fm m 550 kfl lO 110

IIHiz m ore lh an it affects television and FM rd riio wlliill 11eldle in

lreq uency bands above 50 Mhz

i1a n - l11ade noise sources include high-voltage po( rl1 n ( corona dlS shy

charge COilllllUla to r-generated nOISE In electrica l lnotors aliturT10hik d

aircran 19ni t ion nOlse and switching-gear 1l00se Ign H lon n01~e (Hid

sWltching noise like atmospheric nOIse are Imru ls ivc in c Wfa uel lmpuhc

noise is Ih e predominant type of nOIse In switched vrc ll ne c hl lllwls gt11111

as lc1cphone channels For applicatlOlls such as Olee I rdJLsnli~si o I

Imp ulse noise is only an irritation factor hovrever It can 1)( ) s~ t J(Hl~

source of error in appilC3tIons involvIng transmIssion of cl lgnal el ata

Yet another importClrlL source of man -- Tn a de noist is LHlio- fr_~ qucncy

transmitters other than the one of Interest NUJSC Ju c to 1t1lcr tc nng

transmItters is commonly referred to as radlO-freq ll l1 cy in I e reTlllC( WFII

RFI IS p anicularly troublesome In SItuations 111 ~hICh i1 I ClC IIIIL dn tcllll ll IS

su bj ect to a high -density tran smitter environrrlen L -1 S Jn rnohdc

connn unications in a large city

Extraterrestrial noise sources include oLir sun and r)t l H~r ho t

heaven lv bodIes such as stars Owing to its high t Clllpcr)tlllT (tlfill(j C) md

rebliey close proximity to the earth the sun is an Intense bUI [UIIUllattiV

localized source of radio energy that extends ovcr a broad rrr-jl1lnry

spectrum Sim ilarly the stars are sources of wlde- iJalld rClth ~ntT0middot

Although m uch more distant and hence less ink n s e Ih lI1 t i l S II Il

7

nevertheless thev are collectively an importan t source o r n Oi s e IJCT 1 1 ~( n[

their vast numbers Radio stars such as quasars ltl nci p u lsm tgt t ~lbo

In l fnSe sources u f radio energy Considered a Sig ll Zll 5r1L1n c h v n~c1ln

astrCllt Omers such stars are vieved as anolher nlnSl oour( c bv

com nlun lc atlOlls l n gIneers The frequency f clngc or ~ oln r lind ( i JSIIlI C r1l)t~ C

exlends [rom a [evil megahertz to a fevv g igltlh e r t7 - 110Ih( 1 SOU l CC 01

Interference In communication systems is m u ltiple l r d ll s m ic clt)ll pt th s

These can resull from reflection off b u il d in gs th e (]rlh rp ln IK S lJleI

ShIpS or [rom refraclion by stratifications In the lranS ITlI S lt lnn Il t dlllln If

the scattering mechanism results in numerous [(fleeted (umpH1cnls be

received multipatb signal is noiselike and is ter m ed (l i(i 5e If lil e ITlUIUI l h

slgnal componen t IS composed of only one or tVO s lTnng 11 l tT tmiddotd fnv s 11 i ~

termed specular Finally signal degradatlOl1 In a corntn LtJl1 CiJ t0l1 ~ middot ~Ll nl C 1l1

occur because of random changes in attenuallOn w ilh lll 1 h e lril llSTn is SH11l

medium Such signal perturbations (disturbances) are rde n-cd Ln CiS Ji ) )

altbou g h it should be noted that specular m u itlp 1[h abo rcs llits III l l1 rlil1 ~

due to th e constructive and destructive interferen ce uf the Fltlird IIllllLlpk

signals

Typical usesFrequency Name Microwave Band (GHz)Band

Lon rnnsc n [11gnllon snnn r3 -30k l-l z c ry low frequency

Nai gatlonai 81tb rl(ilu30-300kHz Low frequen cy

IMm l imt nl liJo cli~ t I J S~ ilL Cmiddot1 11lJ1g cliree tlJ )1l flllcling COltlsl (jlla rd (( 111 111 lPnlIHLnlal IM rltIi S c IILIl m Ic c lc

nircrnfL Cllnl il l it ll

300-3000 Medium frequ en cy

ships telcgrmiddotp il tr lepllnne anu facsimd e ~llJp- flt- C iJ ~ t

3 - 30~ll-Iz High frequen cy (I-IF

VHF t eleJ~ioJl ( lhlnnltl 5 11 radio land lrdllltpOrlllinn

30-300 Very high frequency

private GHl c raft (tll t raffic cont rol laxi C Ilgt policr navlga noTlftl ltli ds

UHF tc IILgt n l hJIllll is raclto ~() n d( 11 1 I iris

03-3 Gl-lz Ultrahigh frequency 05- 10

suncd lI1lt( r ld r sw l i ite comm 1a dio ltiml le rs

20-30 30-40 40-6 0

10-2 0

s aleii lC lIlI1 lll Jldi~ alillh lc r 1l1l Cn)~1 illk~

Superhigh freq uency 60-80 3-30GI-lL

80- 100 airborn e rlc1 ar ltlpp rnarh radar middottotile r rdciar com m on

10- 124 citrrier Inn d m ollc 30-311lt] Extremel y hig h timiddotcq Rlilroad sen icc rOldOlr Iltlding

800-40 000 Infrared (80- 400) 10Hz) ~m

40k-75k Vis ible light (40-80) ~ tn Optl c01I C() llll JlL1 n11 ti (n~

GHz S vs tCln 75000- 1O~ 1 Ultrav iolet ligh t (12-40 ~ I r

G lIz wt1lltlcnq thj

Table 22 Frequ e ncy Bands With TypIcal Uses ([dc I to Reference II))

9

In ternal nOIse resu lts from th e random motIO n o f charge ca rri- in

e lect roni c com ponen ts It can be of two general types Iderrcd to s thermal

n(js e ca u sed by the random motion of free dcc rons In crmri u or or

SClnlCO n u c tor ~xci ted by th erm al agitation and shot 110 ~dtl cd by th e

runcom arrl aJ or discre te charge carriers 111 sllrh c1e lc( as lhen rllnnLc

tubes and semicondu ctor junc tion dev ices

2 2 Baseband signal types

We a re cons idering th e s ignals only a fter they have bCI OIne ek tnmiddott 1

s Igna ls s ta rt off in non-e lectncal fo rm (eg VOIce t-m per Itun) htlt 11(

been co nve rted to vo ltage u s ing some form o f tra n sdllce Ie g mluphollr middot

thermoeoll p ie)

These e lec trical sign als form the origina l Il1for lllttioll Illch i~ 10 he middot Ilt

the baseband O nce obtai ned they III always flli Il1 ln nc 01 two i)n)d

c la sses

221 Analogue signals

In these Ihe electri cal s igna l s h ows a contmu ous vari lt1l1 Ol1 II I rtmr five r a

wide ra nge of m agni tu des Ofte n th s tim e vanatton s the e Ll h tt of

an original non-elec trical signaJ (eg au preSSlll ltI nc ( I t ~gf In

microphone) so that the two arc sa Id to be ana logou s IWllce he nme of

analogue s ignal

Digital signals

IhcOsc e lec tr ica l siglla ls consi~ ( o r d iscontinuuus pu bes (or di ~It1 elel CIIIla lll ill

duc bu ciJ ltJ ngi ng tbluptl y tiom one d igi t to the nex l I lte Ire ll SI Idl ) led

S i t~lla l s as in a ld c~ prinl e r The most common type is o f cU UJC hill~ll ( lIdinL Ih Il

-- --

ABSTRAK

_

Powered intercom adalah salah smu tekno logi wg l(f hal ll d ldm

sistem kOlTIllnikasi Dengan erti kata lalll ia men of(u nalcan Sl lmbtT k il(lgtltl

sebagal medium perantaraan La m enyerLtp a l dcnf~an in l t J(ol n t rlrl p I rl r

dim ana kabe l dan kebolehan tekmkal tidak dipcrlukan d ll) m pCIW Jlll buJl111

a nt ara in tercom dengan yang lain Powered inlercom bolch rncng h l l] r eLm

m cncri m a data te lapi tidak di daJam satu m asa (scparu h d uplex) 1T[(ci

inte rcom a m a t sesu a i untuk kegunaan di rllmah ulLl pejltJiJd l d im altl j II ilk

antara satu intercorn dengan yang lain ialah ki ra -kJra 1500 k ltJl i ra JU Jl

m empllnya i 3 salura n dimana ia bolh ditingka tka n sebanya k S salu rall (ami l

sesuai) Setiap salUl-an boleh menghublln gi anta ra s at Lt sami Llin des

m en ukarkan s ui sn ya Olch itu ia lebill berkesan b Ibcll1 ci IllR 1 11 [( s ed 1lt11

dimallCl h anya satu yang dapat men ghantar dla Unt lrl m d dll lll] l

selanjutnya m engenai ciri-ClIi aplikasi dan pCmaS8 I1~ltHl a ka n ~lthT-llgk an ltlgi

el i d a lam laporan in

IUltI hrdmRI ~hklurnal ~adtl1l1 11 tK 111 Ml ~ - AI 1_

Conte nt

Chapt e r 1 Introduction

11 Introduc tion 12 Objectives an d a im of the project

Cha pt e r 2 Lit e r a ture Review

2 1 2 1 2 12

2 2 2 21 22 2 22 3 22 4 225

23 2 3 1 232

24 24 2 4 2

2 5 25 1 252

26 26 1

Wha t is communication Block Diaf middotam C h an n el Charac te ristics

Baseba nd s ign al types An a logu ej Digi tal sIgn als Base band and tcrmmalogy Class ification of modula tion types Advantages modu lation Analogue modulation

Multiplexing Frequen cy Trans mitte r Autom o tic Frequency Control of FM gene ral()r

Frequen cy Modula ted Radio Receiver Genelmiddotal Compon ent Des ign

Di s to rti o n And Noise Delay Di sto rtion No ise

Sign a l to No ise Ra tio Baseba nd System s

Page

2

1(1

I I 14 14 14

16 20 )_

J 1 14

11 c7

4

32

Chapter 3 Schematic Design and Components

3 1 SchematJc Design Components and Block diagram

Chapter 4 Results and Analysis

4 1 Power Supply 2 C-MOS Digital inverter (CD 4069)

43 Tone Decode r (LM567) 44 Audio Amplifier (LM386)

45 Outpu t of th e system

Conclusion and Recommendations Chapter 5

511

59

(0 62

11 )

hll 71

7 2

List of Figures

Figure Description Page

2 1 Block d iagram of communi cation sys te m

22 0 Classes o f s ign al I I

22 1 Frequ ency Divis ion MuJti plex concept IIgt

222 Frequen cy Division Multi p lexing

(a ) FM (b)FDM (c) Baseband s pctrum lY

23 1 Basic FM Generato r 21

2 32 Im proved PM Generato r l

233 PM gen erator wilh AFC circu it 2 1

234 Block d iagram of Lim ite r r ~-

235 Diagram uf Preampli fier 26

2 36 Im provement of symmetric clippe r 27

2 3 7 Charac teri s tic of frequen cy to am pli tude H

2 38 The u se of double-tu ned circui t 30

bull 124 1 Block d iagram of domes tic recelver ~

242 Fosley Seeley Discrimina lo r 3Y

243 Diagra m of Quadrature de tec to r -to

2 4 4 Phase shift 4 1

245 Block d iagram of gtbase Locked loop 43

25 I Typicl l ifferentlal de lay H

252 Typical Amplitu de vs Frequency respon se 46

255 Probabili ty of Bit Erro r in

261 Baseband System 33

57Schem a ti c Design O [ Powered In te rcom3 0

- 1 3 1 1 Block diagram o[ in tercom system shy

4 1 0 (a ) Sch em a ti c power s upp ly

roIb) Physical -ollage regulator

6 4 1(a) Inpu t powe r s u p ply s ign a l

6 1 4 J (b) Outpu t s ignal

024 2(a ) Gate tra n s fer

142 ()) Power d iss ipa tion vs Frequ ency

42(c) S ign a l Input of inve rter 03

1)442(d) S ignal oUlput of inverte r

(54 3 (a ) S ign al mput of lone decode r

fgt)4 3 ()) S ign al of ca pac itor timin g

6r43(c) S ignal of resistor tim ing

Uh43 (c) S ign al [ter through 2 K res is to r

(I4 3 (e) S ig11 a l after throu gh 2 2 K resisto r

h7 Signal after thro ugh 27 K res is tor 43(f)

(g43(g) Outp u t of tone decod er

6944 I(a) Inpu t (+) of ampli fie r

4 4 lib) In pu t ( ) of ampli fi er I))

44 I (e) Ou tput Sign al of a mplifie r 70

70 44 fel) VolLage source of amplifi er

4 5 Sys te m ou tput s ignal 7

List Of Tables

Table Dcscript Ion

9Frequency band21

12 22 1 Types of Baseband Signal

253 Requirement fo r two or mUltipoint 46

254 Requirem ent for two or multJ point for

47Envelope del ay distortion

Chapter 1

Introduction of Powered Intercom Project

Introduction

A vast n e twork telecommunicatIOn llllks spans tltc in duS Trilaquolt zcd

COU ntne of the world carrymg telephone te legraph tclcvi ion n e5

p h ologra phs a nd ra dio programs ThIS n e twork IS con stro n llv heing

exp a nded a nd n ew invention s are increasin g its capaCIty ltIt breathtnllt lI1g

ra te The re were m any proble ms we have en cou ntered in th e bq~i l I inf( bu t

s lowly soluti on s have been found We have learn ed to li se the IlI1 llts m o re

e ffi c ie ntly a nd th e cos ts have dropped dramatIc a lly Nowodays there ltIre

m a n y typ es of links that has been use d to com mUI1lCCllr an ti Ilslng the

power su pply to co mmunicate is a new method

Inter com technology has been found 111 ea rlv 1 9~) Os ami s lowl It s

b een expanded to be used in local area network nor WIde lea network

Powered inter com is a new technology where It is slmi l r to lIinkss

intercom However wlreless lntercom IS a system there ~() Ineo n e C(Ul

communicate w1th each other 111 the same small a r ea (h ousr n bllil cll llg)

without using wire d links but for powered intcrcnm SOIneon e ju s t need to

plu g it to th e power supply without worryll1g on h ow to lin k the Inl r](om

By u s ing thi s techno logy it is more con venien t for the c u stomer tu put the

in tercom system s w ith ou t worrym g how to Ill s t ltl ll (mess) w lr(d) and n1lll(

o rganized Neve rtheless a lot o f problems to imple m ent this 1lt11lc o f

sys te m s

For th IS thesis the c haracteris tics on th~ powtrn ml errC)m ~11 1 hI

s tudied befo re Implement the product Neve rth eless thi S repo rt is Iso

s tudy case all the advan ced of telecommuI1Ication s

Chapter 2

Literature Review of Powered Intercom Project

21 WHAT IS COMMUNICATION

211 THE BLOCK DIAGRAM OF A COMMUNICATION SYSTEM

Fi gure 20 shows a cOllullonly used model Il) 1 Cl l l ll 1l l J11 iCl li u ll sy --lun

-l lhough it - lIggcsls a system -or cOllllllunicaLion be1ccn t u ICllhdCh InL~I(t d

or sonar In I hich Ihe system input and output 111 1 be localed 11 Ihe 11e ie

Regardless of the particular application and conli gu-iln II 11l1l1 lmli

trallsmission systems invariably involve three lllZljor sUbSYS tlll l ~~ 11l1bIl1lIloCl Ihl

channeL and d receiver In this literature review we II I lI s lul l bmiddot I h lllkill ~ t11 LLrI1l S

01 systems ror transk r of inforlllation between rcmolch IIK ll ed poi nls II is

limited to such systellls

mes sage message

sgnat

Inp~Jt

transducer T fansmlU8r

carner

Iransmll signal

R8C81ver

addl11ve nOise Interfereflce dls tNtlon res lJolllng from ba~d limlitl119 and non Ilns-cHllls S

c u lpu t ~IJnal

OIJIPll t jrr1sJu cer

Fig 2 I Block d iagram of a communic8 tion sys lcm (Rl fc 10 Re k l llU IIII

2111 Input Transducer

The vide vanety of possible sources of informatlOn refmiddota lll S III ffi JIlV (11 1 h 1r11 1

[arms [or mess a pes Regardless of their exa c t form hOW (lr IncSS rq~~e s 1Tl1 ~

be categorized as analog or digliol The former tTl) be 1ll 1l(lt-lt- cJ s fU Il CIIlt1I 1S

of a continu ous-time variable ([or example press u re t ll n pcrdl lll4 spLrch

mus iC l whereas the latter consist of discrete symbols (for rX d rnpk 1 nlt tl

text) Almost lIwanably the message produced by a sOll rce mbl be

converted bv a transducer to a for m SUItable for til c p ltrti cul r I pe f

cnrn mU111Calion system employed For CX2lillplc 111 elre t riri11

com tT1urlicarions speech waves are converted b cl nllCiUphullf Lo nll ~e

variatIons Sucl a converted 11leSsage is referred to as 111( Incssnrlf siqnu

In thi s book therefore a signal can be Interpreted as the tmiddotu idtin l1 01 a

qua n tIty often a vOlt2gC or current with ti me

2112 Transmitter

The purpose of the transmitter is to couple the mc~sI1~ Lo Llw ~ (Inll c l

Altho ugh it is not uncommon to find the input transd u ce l dll l c lv u lu plcc1

to the trans111ission medium as for example in some interLonl s stC1l1~ iL is

often nccessary to modulate a carrier wave With the s lgn 1 flillTI tile 1111111

transducer Modulation is the systematic vanation 0 1 some illlni) u ll o f Ill

carrier such as amplitude) phase or frequency in alc nrd d l1Ce 1111

function of th e n1essage slgnal There are several reasons f(gt r 11 ing (~rncr

and modulating it Important ones are (l l for ease of ra ci lduo n 1 10 red u ce

noise and interference (3) for channel assignment (4 ) for m Ultiplex ing or

transmlssion of several messages over a single chnnnc1 ln cl (5 I f J U VL rCO ITI l

equipment limitations Several of these reasons are scJf-explanHory Olhns

such as the second ill become more mcaningfui later

In additIOn to modulation other primary functions performed by the

transmi tter a r c fil tering amplillcation and coup ling th e moct u[ed s ipnaJ tu

the channel Ifor example through an antenna or o th e r 1 pprl1 pr JIC c ( ICT I

4

PIIlt1II Ihidmftl lJaklumul H~drlUil Unl c r Sl ll Nl 1aV S1lt1 S arn~n k UNIVEllt~nl MILnSr ~~ w

2 11 3 Channel

Tl w channel can have m any different for m s the most [amil iaL pc-h p is

rh e channel that exists between tlI e transmittin g an ten n a nl ) c OlTImLrLlnl

radio s tat ion and the receivIng antenna of a rad i() 111 thi 5 ch ~ nIH1 the

transmitted slgn al propagates through the 8 trn ospllfr e Dr fn e s Pju rr t il e

receli1ng antenna Hoovever it is not uncommon to Jlnd lhl~ trlnnlI1lcr

hard-wired to the receiver as in most local te lephone syste m s Th S -hlnnl

is vastly differen t from the radio example However ~ I ~ htnncls hC1H )lIe

th ing in common the signal undergoes d egradation fn ln lld I1 S ll11 tr f 1 I

receiver Although this degradatIOn may occur at ~m POlllt or 1I

communication system block diagram lt is customan iy i1 S S~t( l ~ llC d t th lil t

channe1 alone This degrad a tion often results from nOl sc rll rl qhr r lin(lt-

on-ed signals or lIlterference but also may lIlclude o lh er (hSLO I UOll cllcLh 1S

Nell such as fad lng signallcvels multiple transIniss io n P ill-h s 8nd fillr nnf

More about these unwanted perturbatIOns will be pr esented llo lll v

2114 Receiver

The receivers fu n ction is to extract the desIred messag( lrofll Imiddothe ITr-I~ I f d

signal at the ch ill1nel output and to convert It to fUI In Sl lltlhle f lll lit

output transducer Although amplification rn3 be 11IIC or ti ll IIfb l Il

atlons per[onned by the receiver especially in radio ( ()TIl11l1nllal J1) I1 ~ ) wh(n

lhe recelved Si gn al m ay be extremely weak the rn __ ~ i ll Junc lio n uf dH r L l l I C i

is to demodula ie the received signal Oft en It IS d es ire d th lI rcCCIIl rl( output be a scaled possibly delayed version of th e mcssd gc s iYIrI I I h e

modli lator mput although in some cases a morc ge n creo l rnnclo ll I Ih e

input rnessage is desired However as a result of the p re s cll (c or nO ise d nd

distortion tlus operatIOn is less than ldeal Ways of ~pprn ] hillg Illl k11

5

case of perfec t recovery wi ll be discussed as we p roceed

211 5 Output Transducer

The outpu t transdu cer completes the communicatIOn svstem This knee

converts th e el~Ll ic s Ignal at its in pu t InLO t he f rm c1csll(d hv I he svsIt m

u ser Perh aps the m os t common OUlput tran sdu cer IS 1Iucl spIkcr

However the re ar e many oth er examples s u ch as tltlpe rccorckrs pers0I w]

computers meters and cath ode-r ay tubes an d etc

212 CHANNEL CHARACTERISTICS

Noise Sources

No ise in a co mmunica tion sys tem can be cl lsslficcl Jt1 to two 1-1 lt1

categori es depend ing on its source Noise generated bv compone nt w it hll1

a co mmunication system s u ch as resis tors eicclron lubes ii nel sol U-llI(

acti ve devices is referr ed to as internal nOise The second ca tc~nr p~l( rnal

noise r esults from sources out s ide a commul11cation system 1IIclLllthr

a tmospheri c man -m a de and extrate rrestrial sou rces

Atmospheri c noise results primarily fro m SP Uri O U S )dl n wmTS

gen erated by the n a tural e lec trical d ischarges wit llll the t111uraquoph ltl

a ssocia ted with thunderstorms It is commonly rcfc rrrd to rl S 1)11( or

spitcncs Below about 100 MHz th e fi e ld s trcl12th of such radw 1 o- S IS

in ve rsely propo rtio na l to frequen cy Almosph en c II IHSC IS Lh Ii ln IZf d 011

the time do m ai n by largeamplitude s ho rt-dura tion bu rs ls lild IS nne of t illt

p rime examples o f n oise refe rred to as trl)I)[il~I(~ RecltlIlgte of llq i The

6

dependence on frequency atmospheric nOIse 8ffcrs ( CllllnWrCIltl1 A) l

broadcast radio which occupies the frequency ra n flc fm m 550 kfl lO 110

IIHiz m ore lh an it affects television and FM rd riio wlliill 11eldle in

lreq uency bands above 50 Mhz

i1a n - l11ade noise sources include high-voltage po( rl1 n ( corona dlS shy

charge COilllllUla to r-generated nOISE In electrica l lnotors aliturT10hik d

aircran 19ni t ion nOlse and switching-gear 1l00se Ign H lon n01~e (Hid

sWltching noise like atmospheric nOIse are Imru ls ivc in c Wfa uel lmpuhc

noise is Ih e predominant type of nOIse In switched vrc ll ne c hl lllwls gt11111

as lc1cphone channels For applicatlOlls such as Olee I rdJLsnli~si o I

Imp ulse noise is only an irritation factor hovrever It can 1)( ) s~ t J(Hl~

source of error in appilC3tIons involvIng transmIssion of cl lgnal el ata

Yet another importClrlL source of man -- Tn a de noist is LHlio- fr_~ qucncy

transmitters other than the one of Interest NUJSC Ju c to 1t1lcr tc nng

transmItters is commonly referred to as radlO-freq ll l1 cy in I e reTlllC( WFII

RFI IS p anicularly troublesome In SItuations 111 ~hICh i1 I ClC IIIIL dn tcllll ll IS

su bj ect to a high -density tran smitter environrrlen L -1 S Jn rnohdc

connn unications in a large city

Extraterrestrial noise sources include oLir sun and r)t l H~r ho t

heaven lv bodIes such as stars Owing to its high t Clllpcr)tlllT (tlfill(j C) md

rebliey close proximity to the earth the sun is an Intense bUI [UIIUllattiV

localized source of radio energy that extends ovcr a broad rrr-jl1lnry

spectrum Sim ilarly the stars are sources of wlde- iJalld rClth ~ntT0middot

Although m uch more distant and hence less ink n s e Ih lI1 t i l S II Il

7

nevertheless thev are collectively an importan t source o r n Oi s e IJCT 1 1 ~( n[

their vast numbers Radio stars such as quasars ltl nci p u lsm tgt t ~lbo

In l fnSe sources u f radio energy Considered a Sig ll Zll 5r1L1n c h v n~c1ln

astrCllt Omers such stars are vieved as anolher nlnSl oour( c bv

com nlun lc atlOlls l n gIneers The frequency f clngc or ~ oln r lind ( i JSIIlI C r1l)t~ C

exlends [rom a [evil megahertz to a fevv g igltlh e r t7 - 110Ih( 1 SOU l CC 01

Interference In communication systems is m u ltiple l r d ll s m ic clt)ll pt th s

These can resull from reflection off b u il d in gs th e (]rlh rp ln IK S lJleI

ShIpS or [rom refraclion by stratifications In the lranS ITlI S lt lnn Il t dlllln If

the scattering mechanism results in numerous [(fleeted (umpH1cnls be

received multipatb signal is noiselike and is ter m ed (l i(i 5e If lil e ITlUIUI l h

slgnal componen t IS composed of only one or tVO s lTnng 11 l tT tmiddotd fnv s 11 i ~

termed specular Finally signal degradatlOl1 In a corntn LtJl1 CiJ t0l1 ~ middot ~Ll nl C 1l1

occur because of random changes in attenuallOn w ilh lll 1 h e lril llSTn is SH11l

medium Such signal perturbations (disturbances) are rde n-cd Ln CiS Ji ) )

altbou g h it should be noted that specular m u itlp 1[h abo rcs llits III l l1 rlil1 ~

due to th e constructive and destructive interferen ce uf the Fltlird IIllllLlpk

signals

Typical usesFrequency Name Microwave Band (GHz)Band

Lon rnnsc n [11gnllon snnn r3 -30k l-l z c ry low frequency

Nai gatlonai 81tb rl(ilu30-300kHz Low frequen cy

IMm l imt nl liJo cli~ t I J S~ ilL Cmiddot1 11lJ1g cliree tlJ )1l flllcling COltlsl (jlla rd (( 111 111 lPnlIHLnlal IM rltIi S c IILIl m Ic c lc

nircrnfL Cllnl il l it ll

300-3000 Medium frequ en cy

ships telcgrmiddotp il tr lepllnne anu facsimd e ~llJp- flt- C iJ ~ t

3 - 30~ll-Iz High frequen cy (I-IF

VHF t eleJ~ioJl ( lhlnnltl 5 11 radio land lrdllltpOrlllinn

30-300 Very high frequency

private GHl c raft (tll t raffic cont rol laxi C Ilgt policr navlga noTlftl ltli ds

UHF tc IILgt n l hJIllll is raclto ~() n d( 11 1 I iris

03-3 Gl-lz Ultrahigh frequency 05- 10

suncd lI1lt( r ld r sw l i ite comm 1a dio ltiml le rs

20-30 30-40 40-6 0

10-2 0

s aleii lC lIlI1 lll Jldi~ alillh lc r 1l1l Cn)~1 illk~

Superhigh freq uency 60-80 3-30GI-lL

80- 100 airborn e rlc1 ar ltlpp rnarh radar middottotile r rdciar com m on

10- 124 citrrier Inn d m ollc 30-311lt] Extremel y hig h timiddotcq Rlilroad sen icc rOldOlr Iltlding

800-40 000 Infrared (80- 400) 10Hz) ~m

40k-75k Vis ible light (40-80) ~ tn Optl c01I C() llll JlL1 n11 ti (n~

GHz S vs tCln 75000- 1O~ 1 Ultrav iolet ligh t (12-40 ~ I r

G lIz wt1lltlcnq thj

Table 22 Frequ e ncy Bands With TypIcal Uses ([dc I to Reference II))

9

In ternal nOIse resu lts from th e random motIO n o f charge ca rri- in

e lect roni c com ponen ts It can be of two general types Iderrcd to s thermal

n(js e ca u sed by the random motion of free dcc rons In crmri u or or

SClnlCO n u c tor ~xci ted by th erm al agitation and shot 110 ~dtl cd by th e

runcom arrl aJ or discre te charge carriers 111 sllrh c1e lc( as lhen rllnnLc

tubes and semicondu ctor junc tion dev ices

2 2 Baseband signal types

We a re cons idering th e s ignals only a fter they have bCI OIne ek tnmiddott 1

s Igna ls s ta rt off in non-e lectncal fo rm (eg VOIce t-m per Itun) htlt 11(

been co nve rted to vo ltage u s ing some form o f tra n sdllce Ie g mluphollr middot

thermoeoll p ie)

These e lec trical sign als form the origina l Il1for lllttioll Illch i~ 10 he middot Ilt

the baseband O nce obtai ned they III always flli Il1 ln nc 01 two i)n)d

c la sses

221 Analogue signals

In these Ihe electri cal s igna l s h ows a contmu ous vari lt1l1 Ol1 II I rtmr five r a

wide ra nge of m agni tu des Ofte n th s tim e vanatton s the e Ll h tt of

an original non-elec trical signaJ (eg au preSSlll ltI nc ( I t ~gf In

microphone) so that the two arc sa Id to be ana logou s IWllce he nme of

analogue s ignal

Digital signals

IhcOsc e lec tr ica l siglla ls consi~ ( o r d iscontinuuus pu bes (or di ~It1 elel CIIIla lll ill

duc bu ciJ ltJ ngi ng tbluptl y tiom one d igi t to the nex l I lte Ire ll SI Idl ) led

S i t~lla l s as in a ld c~ prinl e r The most common type is o f cU UJC hill~ll ( lIdinL Ih Il

IUltI hrdmRI ~hklurnal ~adtl1l1 11 tK 111 Ml ~ - AI 1_

Conte nt

Chapt e r 1 Introduction

11 Introduc tion 12 Objectives an d a im of the project

Cha pt e r 2 Lit e r a ture Review

2 1 2 1 2 12

2 2 2 21 22 2 22 3 22 4 225

23 2 3 1 232

24 24 2 4 2

2 5 25 1 252

26 26 1

Wha t is communication Block Diaf middotam C h an n el Charac te ristics

Baseba nd s ign al types An a logu ej Digi tal sIgn als Base band and tcrmmalogy Class ification of modula tion types Advantages modu lation Analogue modulation

Multiplexing Frequen cy Trans mitte r Autom o tic Frequency Control of FM gene ral()r

Frequen cy Modula ted Radio Receiver Genelmiddotal Compon ent Des ign

Di s to rti o n And Noise Delay Di sto rtion No ise

Sign a l to No ise Ra tio Baseba nd System s

Page

2

1(1

I I 14 14 14

16 20 )_

J 1 14

11 c7

4

32

Chapter 3 Schematic Design and Components

3 1 SchematJc Design Components and Block diagram

Chapter 4 Results and Analysis

4 1 Power Supply 2 C-MOS Digital inverter (CD 4069)

43 Tone Decode r (LM567) 44 Audio Amplifier (LM386)

45 Outpu t of th e system

Conclusion and Recommendations Chapter 5

511

59

(0 62

11 )

hll 71

7 2

List of Figures

Figure Description Page

2 1 Block d iagram of communi cation sys te m

22 0 Classes o f s ign al I I

22 1 Frequ ency Divis ion MuJti plex concept IIgt

222 Frequen cy Division Multi p lexing

(a ) FM (b)FDM (c) Baseband s pctrum lY

23 1 Basic FM Generato r 21

2 32 Im proved PM Generato r l

233 PM gen erator wilh AFC circu it 2 1

234 Block d iagram of Lim ite r r ~-

235 Diagram uf Preampli fier 26

2 36 Im provement of symmetric clippe r 27

2 3 7 Charac teri s tic of frequen cy to am pli tude H

2 38 The u se of double-tu ned circui t 30

bull 124 1 Block d iagram of domes tic recelver ~

242 Fosley Seeley Discrimina lo r 3Y

243 Diagra m of Quadrature de tec to r -to

2 4 4 Phase shift 4 1

245 Block d iagram of gtbase Locked loop 43

25 I Typicl l ifferentlal de lay H

252 Typical Amplitu de vs Frequency respon se 46

255 Probabili ty of Bit Erro r in

261 Baseband System 33

57Schem a ti c Design O [ Powered In te rcom3 0

- 1 3 1 1 Block diagram o[ in tercom system shy

4 1 0 (a ) Sch em a ti c power s upp ly

roIb) Physical -ollage regulator

6 4 1(a) Inpu t powe r s u p ply s ign a l

6 1 4 J (b) Outpu t s ignal

024 2(a ) Gate tra n s fer

142 ()) Power d iss ipa tion vs Frequ ency

42(c) S ign a l Input of inve rter 03

1)442(d) S ignal oUlput of inverte r

(54 3 (a ) S ign al mput of lone decode r

fgt)4 3 ()) S ign al of ca pac itor timin g

6r43(c) S ignal of resistor tim ing

Uh43 (c) S ign al [ter through 2 K res is to r

(I4 3 (e) S ig11 a l after throu gh 2 2 K resisto r

h7 Signal after thro ugh 27 K res is tor 43(f)

(g43(g) Outp u t of tone decod er

6944 I(a) Inpu t (+) of ampli fie r

4 4 lib) In pu t ( ) of ampli fi er I))

44 I (e) Ou tput Sign al of a mplifie r 70

70 44 fel) VolLage source of amplifi er

4 5 Sys te m ou tput s ignal 7

List Of Tables

Table Dcscript Ion

9Frequency band21

12 22 1 Types of Baseband Signal

253 Requirement fo r two or mUltipoint 46

254 Requirem ent for two or multJ point for

47Envelope del ay distortion

Chapter 1

Introduction of Powered Intercom Project

Introduction

A vast n e twork telecommunicatIOn llllks spans tltc in duS Trilaquolt zcd

COU ntne of the world carrymg telephone te legraph tclcvi ion n e5

p h ologra phs a nd ra dio programs ThIS n e twork IS con stro n llv heing

exp a nded a nd n ew invention s are increasin g its capaCIty ltIt breathtnllt lI1g

ra te The re were m any proble ms we have en cou ntered in th e bq~i l I inf( bu t

s lowly soluti on s have been found We have learn ed to li se the IlI1 llts m o re

e ffi c ie ntly a nd th e cos ts have dropped dramatIc a lly Nowodays there ltIre

m a n y typ es of links that has been use d to com mUI1lCCllr an ti Ilslng the

power su pply to co mmunicate is a new method

Inter com technology has been found 111 ea rlv 1 9~) Os ami s lowl It s

b een expanded to be used in local area network nor WIde lea network

Powered inter com is a new technology where It is slmi l r to lIinkss

intercom However wlreless lntercom IS a system there ~() Ineo n e C(Ul

communicate w1th each other 111 the same small a r ea (h ousr n bllil cll llg)

without using wire d links but for powered intcrcnm SOIneon e ju s t need to

plu g it to th e power supply without worryll1g on h ow to lin k the Inl r](om

By u s ing thi s techno logy it is more con venien t for the c u stomer tu put the

in tercom system s w ith ou t worrym g how to Ill s t ltl ll (mess) w lr(d) and n1lll(

o rganized Neve rtheless a lot o f problems to imple m ent this 1lt11lc o f

sys te m s

For th IS thesis the c haracteris tics on th~ powtrn ml errC)m ~11 1 hI

s tudied befo re Implement the product Neve rth eless thi S repo rt is Iso

s tudy case all the advan ced of telecommuI1Ication s

Chapter 2

Literature Review of Powered Intercom Project

21 WHAT IS COMMUNICATION

211 THE BLOCK DIAGRAM OF A COMMUNICATION SYSTEM

Fi gure 20 shows a cOllullonly used model Il) 1 Cl l l ll 1l l J11 iCl li u ll sy --lun

-l lhough it - lIggcsls a system -or cOllllllunicaLion be1ccn t u ICllhdCh InL~I(t d

or sonar In I hich Ihe system input and output 111 1 be localed 11 Ihe 11e ie

Regardless of the particular application and conli gu-iln II 11l1l1 lmli

trallsmission systems invariably involve three lllZljor sUbSYS tlll l ~~ 11l1bIl1lIloCl Ihl

channeL and d receiver In this literature review we II I lI s lul l bmiddot I h lllkill ~ t11 LLrI1l S

01 systems ror transk r of inforlllation between rcmolch IIK ll ed poi nls II is

limited to such systellls

mes sage message

sgnat

Inp~Jt

transducer T fansmlU8r

carner

Iransmll signal

R8C81ver

addl11ve nOise Interfereflce dls tNtlon res lJolllng from ba~d limlitl119 and non Ilns-cHllls S

c u lpu t ~IJnal

OIJIPll t jrr1sJu cer

Fig 2 I Block d iagram of a communic8 tion sys lcm (Rl fc 10 Re k l llU IIII

2111 Input Transducer

The vide vanety of possible sources of informatlOn refmiddota lll S III ffi JIlV (11 1 h 1r11 1

[arms [or mess a pes Regardless of their exa c t form hOW (lr IncSS rq~~e s 1Tl1 ~

be categorized as analog or digliol The former tTl) be 1ll 1l(lt-lt- cJ s fU Il CIIlt1I 1S

of a continu ous-time variable ([or example press u re t ll n pcrdl lll4 spLrch

mus iC l whereas the latter consist of discrete symbols (for rX d rnpk 1 nlt tl

text) Almost lIwanably the message produced by a sOll rce mbl be

converted bv a transducer to a for m SUItable for til c p ltrti cul r I pe f

cnrn mU111Calion system employed For CX2lillplc 111 elre t riri11

com tT1urlicarions speech waves are converted b cl nllCiUphullf Lo nll ~e

variatIons Sucl a converted 11leSsage is referred to as 111( Incssnrlf siqnu

In thi s book therefore a signal can be Interpreted as the tmiddotu idtin l1 01 a

qua n tIty often a vOlt2gC or current with ti me

2112 Transmitter

The purpose of the transmitter is to couple the mc~sI1~ Lo Llw ~ (Inll c l

Altho ugh it is not uncommon to find the input transd u ce l dll l c lv u lu plcc1

to the trans111ission medium as for example in some interLonl s stC1l1~ iL is

often nccessary to modulate a carrier wave With the s lgn 1 flillTI tile 1111111

transducer Modulation is the systematic vanation 0 1 some illlni) u ll o f Ill

carrier such as amplitude) phase or frequency in alc nrd d l1Ce 1111

function of th e n1essage slgnal There are several reasons f(gt r 11 ing (~rncr

and modulating it Important ones are (l l for ease of ra ci lduo n 1 10 red u ce

noise and interference (3) for channel assignment (4 ) for m Ultiplex ing or

transmlssion of several messages over a single chnnnc1 ln cl (5 I f J U VL rCO ITI l

equipment limitations Several of these reasons are scJf-explanHory Olhns

such as the second ill become more mcaningfui later

In additIOn to modulation other primary functions performed by the

transmi tter a r c fil tering amplillcation and coup ling th e moct u[ed s ipnaJ tu

the channel Ifor example through an antenna or o th e r 1 pprl1 pr JIC c ( ICT I

4

PIIlt1II Ihidmftl lJaklumul H~drlUil Unl c r Sl ll Nl 1aV S1lt1 S arn~n k UNIVEllt~nl MILnSr ~~ w

2 11 3 Channel

Tl w channel can have m any different for m s the most [amil iaL pc-h p is

rh e channel that exists between tlI e transmittin g an ten n a nl ) c OlTImLrLlnl

radio s tat ion and the receivIng antenna of a rad i() 111 thi 5 ch ~ nIH1 the

transmitted slgn al propagates through the 8 trn ospllfr e Dr fn e s Pju rr t il e

receli1ng antenna Hoovever it is not uncommon to Jlnd lhl~ trlnnlI1lcr

hard-wired to the receiver as in most local te lephone syste m s Th S -hlnnl

is vastly differen t from the radio example However ~ I ~ htnncls hC1H )lIe

th ing in common the signal undergoes d egradation fn ln lld I1 S ll11 tr f 1 I

receiver Although this degradatIOn may occur at ~m POlllt or 1I

communication system block diagram lt is customan iy i1 S S~t( l ~ llC d t th lil t

channe1 alone This degrad a tion often results from nOl sc rll rl qhr r lin(lt-

on-ed signals or lIlterference but also may lIlclude o lh er (hSLO I UOll cllcLh 1S

Nell such as fad lng signallcvels multiple transIniss io n P ill-h s 8nd fillr nnf

More about these unwanted perturbatIOns will be pr esented llo lll v

2114 Receiver

The receivers fu n ction is to extract the desIred messag( lrofll Imiddothe ITr-I~ I f d

signal at the ch ill1nel output and to convert It to fUI In Sl lltlhle f lll lit

output transducer Although amplification rn3 be 11IIC or ti ll IIfb l Il

atlons per[onned by the receiver especially in radio ( ()TIl11l1nllal J1) I1 ~ ) wh(n

lhe recelved Si gn al m ay be extremely weak the rn __ ~ i ll Junc lio n uf dH r L l l I C i

is to demodula ie the received signal Oft en It IS d es ire d th lI rcCCIIl rl( output be a scaled possibly delayed version of th e mcssd gc s iYIrI I I h e

modli lator mput although in some cases a morc ge n creo l rnnclo ll I Ih e

input rnessage is desired However as a result of the p re s cll (c or nO ise d nd

distortion tlus operatIOn is less than ldeal Ways of ~pprn ] hillg Illl k11

5

case of perfec t recovery wi ll be discussed as we p roceed

211 5 Output Transducer

The outpu t transdu cer completes the communicatIOn svstem This knee

converts th e el~Ll ic s Ignal at its in pu t InLO t he f rm c1csll(d hv I he svsIt m

u ser Perh aps the m os t common OUlput tran sdu cer IS 1Iucl spIkcr

However the re ar e many oth er examples s u ch as tltlpe rccorckrs pers0I w]

computers meters and cath ode-r ay tubes an d etc

212 CHANNEL CHARACTERISTICS

Noise Sources

No ise in a co mmunica tion sys tem can be cl lsslficcl Jt1 to two 1-1 lt1

categori es depend ing on its source Noise generated bv compone nt w it hll1

a co mmunication system s u ch as resis tors eicclron lubes ii nel sol U-llI(

acti ve devices is referr ed to as internal nOise The second ca tc~nr p~l( rnal

noise r esults from sources out s ide a commul11cation system 1IIclLllthr

a tmospheri c man -m a de and extrate rrestrial sou rces

Atmospheri c noise results primarily fro m SP Uri O U S )dl n wmTS

gen erated by the n a tural e lec trical d ischarges wit llll the t111uraquoph ltl

a ssocia ted with thunderstorms It is commonly rcfc rrrd to rl S 1)11( or

spitcncs Below about 100 MHz th e fi e ld s trcl12th of such radw 1 o- S IS

in ve rsely propo rtio na l to frequen cy Almosph en c II IHSC IS Lh Ii ln IZf d 011

the time do m ai n by largeamplitude s ho rt-dura tion bu rs ls lild IS nne of t illt

p rime examples o f n oise refe rred to as trl)I)[il~I(~ RecltlIlgte of llq i The

6

dependence on frequency atmospheric nOIse 8ffcrs ( CllllnWrCIltl1 A) l

broadcast radio which occupies the frequency ra n flc fm m 550 kfl lO 110

IIHiz m ore lh an it affects television and FM rd riio wlliill 11eldle in

lreq uency bands above 50 Mhz

i1a n - l11ade noise sources include high-voltage po( rl1 n ( corona dlS shy

charge COilllllUla to r-generated nOISE In electrica l lnotors aliturT10hik d

aircran 19ni t ion nOlse and switching-gear 1l00se Ign H lon n01~e (Hid

sWltching noise like atmospheric nOIse are Imru ls ivc in c Wfa uel lmpuhc

noise is Ih e predominant type of nOIse In switched vrc ll ne c hl lllwls gt11111

as lc1cphone channels For applicatlOlls such as Olee I rdJLsnli~si o I

Imp ulse noise is only an irritation factor hovrever It can 1)( ) s~ t J(Hl~

source of error in appilC3tIons involvIng transmIssion of cl lgnal el ata

Yet another importClrlL source of man -- Tn a de noist is LHlio- fr_~ qucncy

transmitters other than the one of Interest NUJSC Ju c to 1t1lcr tc nng

transmItters is commonly referred to as radlO-freq ll l1 cy in I e reTlllC( WFII

RFI IS p anicularly troublesome In SItuations 111 ~hICh i1 I ClC IIIIL dn tcllll ll IS

su bj ect to a high -density tran smitter environrrlen L -1 S Jn rnohdc

connn unications in a large city

Extraterrestrial noise sources include oLir sun and r)t l H~r ho t

heaven lv bodIes such as stars Owing to its high t Clllpcr)tlllT (tlfill(j C) md

rebliey close proximity to the earth the sun is an Intense bUI [UIIUllattiV

localized source of radio energy that extends ovcr a broad rrr-jl1lnry

spectrum Sim ilarly the stars are sources of wlde- iJalld rClth ~ntT0middot

Although m uch more distant and hence less ink n s e Ih lI1 t i l S II Il

7

nevertheless thev are collectively an importan t source o r n Oi s e IJCT 1 1 ~( n[

their vast numbers Radio stars such as quasars ltl nci p u lsm tgt t ~lbo

In l fnSe sources u f radio energy Considered a Sig ll Zll 5r1L1n c h v n~c1ln

astrCllt Omers such stars are vieved as anolher nlnSl oour( c bv

com nlun lc atlOlls l n gIneers The frequency f clngc or ~ oln r lind ( i JSIIlI C r1l)t~ C

exlends [rom a [evil megahertz to a fevv g igltlh e r t7 - 110Ih( 1 SOU l CC 01

Interference In communication systems is m u ltiple l r d ll s m ic clt)ll pt th s

These can resull from reflection off b u il d in gs th e (]rlh rp ln IK S lJleI

ShIpS or [rom refraclion by stratifications In the lranS ITlI S lt lnn Il t dlllln If

the scattering mechanism results in numerous [(fleeted (umpH1cnls be

received multipatb signal is noiselike and is ter m ed (l i(i 5e If lil e ITlUIUI l h

slgnal componen t IS composed of only one or tVO s lTnng 11 l tT tmiddotd fnv s 11 i ~

termed specular Finally signal degradatlOl1 In a corntn LtJl1 CiJ t0l1 ~ middot ~Ll nl C 1l1

occur because of random changes in attenuallOn w ilh lll 1 h e lril llSTn is SH11l

medium Such signal perturbations (disturbances) are rde n-cd Ln CiS Ji ) )

altbou g h it should be noted that specular m u itlp 1[h abo rcs llits III l l1 rlil1 ~

due to th e constructive and destructive interferen ce uf the Fltlird IIllllLlpk

signals

Typical usesFrequency Name Microwave Band (GHz)Band

Lon rnnsc n [11gnllon snnn r3 -30k l-l z c ry low frequency

Nai gatlonai 81tb rl(ilu30-300kHz Low frequen cy

IMm l imt nl liJo cli~ t I J S~ ilL Cmiddot1 11lJ1g cliree tlJ )1l flllcling COltlsl (jlla rd (( 111 111 lPnlIHLnlal IM rltIi S c IILIl m Ic c lc

nircrnfL Cllnl il l it ll

300-3000 Medium frequ en cy

ships telcgrmiddotp il tr lepllnne anu facsimd e ~llJp- flt- C iJ ~ t

3 - 30~ll-Iz High frequen cy (I-IF

VHF t eleJ~ioJl ( lhlnnltl 5 11 radio land lrdllltpOrlllinn

30-300 Very high frequency

private GHl c raft (tll t raffic cont rol laxi C Ilgt policr navlga noTlftl ltli ds

UHF tc IILgt n l hJIllll is raclto ~() n d( 11 1 I iris

03-3 Gl-lz Ultrahigh frequency 05- 10

suncd lI1lt( r ld r sw l i ite comm 1a dio ltiml le rs

20-30 30-40 40-6 0

10-2 0

s aleii lC lIlI1 lll Jldi~ alillh lc r 1l1l Cn)~1 illk~

Superhigh freq uency 60-80 3-30GI-lL

80- 100 airborn e rlc1 ar ltlpp rnarh radar middottotile r rdciar com m on

10- 124 citrrier Inn d m ollc 30-311lt] Extremel y hig h timiddotcq Rlilroad sen icc rOldOlr Iltlding

800-40 000 Infrared (80- 400) 10Hz) ~m

40k-75k Vis ible light (40-80) ~ tn Optl c01I C() llll JlL1 n11 ti (n~

GHz S vs tCln 75000- 1O~ 1 Ultrav iolet ligh t (12-40 ~ I r

G lIz wt1lltlcnq thj

Table 22 Frequ e ncy Bands With TypIcal Uses ([dc I to Reference II))

9

In ternal nOIse resu lts from th e random motIO n o f charge ca rri- in

e lect roni c com ponen ts It can be of two general types Iderrcd to s thermal

n(js e ca u sed by the random motion of free dcc rons In crmri u or or

SClnlCO n u c tor ~xci ted by th erm al agitation and shot 110 ~dtl cd by th e

runcom arrl aJ or discre te charge carriers 111 sllrh c1e lc( as lhen rllnnLc

tubes and semicondu ctor junc tion dev ices

2 2 Baseband signal types

We a re cons idering th e s ignals only a fter they have bCI OIne ek tnmiddott 1

s Igna ls s ta rt off in non-e lectncal fo rm (eg VOIce t-m per Itun) htlt 11(

been co nve rted to vo ltage u s ing some form o f tra n sdllce Ie g mluphollr middot

thermoeoll p ie)

These e lec trical sign als form the origina l Il1for lllttioll Illch i~ 10 he middot Ilt

the baseband O nce obtai ned they III always flli Il1 ln nc 01 two i)n)d

c la sses

221 Analogue signals

In these Ihe electri cal s igna l s h ows a contmu ous vari lt1l1 Ol1 II I rtmr five r a

wide ra nge of m agni tu des Ofte n th s tim e vanatton s the e Ll h tt of

an original non-elec trical signaJ (eg au preSSlll ltI nc ( I t ~gf In

microphone) so that the two arc sa Id to be ana logou s IWllce he nme of

analogue s ignal

Digital signals

IhcOsc e lec tr ica l siglla ls consi~ ( o r d iscontinuuus pu bes (or di ~It1 elel CIIIla lll ill

duc bu ciJ ltJ ngi ng tbluptl y tiom one d igi t to the nex l I lte Ire ll SI Idl ) led

S i t~lla l s as in a ld c~ prinl e r The most common type is o f cU UJC hill~ll ( lIdinL Ih Il

32

Chapter 3 Schematic Design and Components

3 1 SchematJc Design Components and Block diagram

Chapter 4 Results and Analysis

4 1 Power Supply 2 C-MOS Digital inverter (CD 4069)

43 Tone Decode r (LM567) 44 Audio Amplifier (LM386)

45 Outpu t of th e system

Conclusion and Recommendations Chapter 5

511

59

(0 62

11 )

hll 71

7 2

List of Figures

Figure Description Page

2 1 Block d iagram of communi cation sys te m

22 0 Classes o f s ign al I I

22 1 Frequ ency Divis ion MuJti plex concept IIgt

222 Frequen cy Division Multi p lexing

(a ) FM (b)FDM (c) Baseband s pctrum lY

23 1 Basic FM Generato r 21

2 32 Im proved PM Generato r l

233 PM gen erator wilh AFC circu it 2 1

234 Block d iagram of Lim ite r r ~-

235 Diagram uf Preampli fier 26

2 36 Im provement of symmetric clippe r 27

2 3 7 Charac teri s tic of frequen cy to am pli tude H

2 38 The u se of double-tu ned circui t 30

bull 124 1 Block d iagram of domes tic recelver ~

242 Fosley Seeley Discrimina lo r 3Y

243 Diagra m of Quadrature de tec to r -to

2 4 4 Phase shift 4 1

245 Block d iagram of gtbase Locked loop 43

25 I Typicl l ifferentlal de lay H

252 Typical Amplitu de vs Frequency respon se 46

255 Probabili ty of Bit Erro r in

261 Baseband System 33

57Schem a ti c Design O [ Powered In te rcom3 0

- 1 3 1 1 Block diagram o[ in tercom system shy

4 1 0 (a ) Sch em a ti c power s upp ly

roIb) Physical -ollage regulator

6 4 1(a) Inpu t powe r s u p ply s ign a l

6 1 4 J (b) Outpu t s ignal

024 2(a ) Gate tra n s fer

142 ()) Power d iss ipa tion vs Frequ ency

42(c) S ign a l Input of inve rter 03

1)442(d) S ignal oUlput of inverte r

(54 3 (a ) S ign al mput of lone decode r

fgt)4 3 ()) S ign al of ca pac itor timin g

6r43(c) S ignal of resistor tim ing

Uh43 (c) S ign al [ter through 2 K res is to r

(I4 3 (e) S ig11 a l after throu gh 2 2 K resisto r

h7 Signal after thro ugh 27 K res is tor 43(f)

(g43(g) Outp u t of tone decod er

6944 I(a) Inpu t (+) of ampli fie r

4 4 lib) In pu t ( ) of ampli fi er I))

44 I (e) Ou tput Sign al of a mplifie r 70

70 44 fel) VolLage source of amplifi er

4 5 Sys te m ou tput s ignal 7

List Of Tables

Table Dcscript Ion

9Frequency band21

12 22 1 Types of Baseband Signal

253 Requirement fo r two or mUltipoint 46

254 Requirem ent for two or multJ point for

47Envelope del ay distortion

Chapter 1

Introduction of Powered Intercom Project

Introduction

A vast n e twork telecommunicatIOn llllks spans tltc in duS Trilaquolt zcd

COU ntne of the world carrymg telephone te legraph tclcvi ion n e5

p h ologra phs a nd ra dio programs ThIS n e twork IS con stro n llv heing

exp a nded a nd n ew invention s are increasin g its capaCIty ltIt breathtnllt lI1g

ra te The re were m any proble ms we have en cou ntered in th e bq~i l I inf( bu t

s lowly soluti on s have been found We have learn ed to li se the IlI1 llts m o re

e ffi c ie ntly a nd th e cos ts have dropped dramatIc a lly Nowodays there ltIre

m a n y typ es of links that has been use d to com mUI1lCCllr an ti Ilslng the

power su pply to co mmunicate is a new method

Inter com technology has been found 111 ea rlv 1 9~) Os ami s lowl It s

b een expanded to be used in local area network nor WIde lea network

Powered inter com is a new technology where It is slmi l r to lIinkss

intercom However wlreless lntercom IS a system there ~() Ineo n e C(Ul

communicate w1th each other 111 the same small a r ea (h ousr n bllil cll llg)

without using wire d links but for powered intcrcnm SOIneon e ju s t need to

plu g it to th e power supply without worryll1g on h ow to lin k the Inl r](om

By u s ing thi s techno logy it is more con venien t for the c u stomer tu put the

in tercom system s w ith ou t worrym g how to Ill s t ltl ll (mess) w lr(d) and n1lll(

o rganized Neve rtheless a lot o f problems to imple m ent this 1lt11lc o f

sys te m s

For th IS thesis the c haracteris tics on th~ powtrn ml errC)m ~11 1 hI

s tudied befo re Implement the product Neve rth eless thi S repo rt is Iso

s tudy case all the advan ced of telecommuI1Ication s

Chapter 2

Literature Review of Powered Intercom Project

21 WHAT IS COMMUNICATION

211 THE BLOCK DIAGRAM OF A COMMUNICATION SYSTEM

Fi gure 20 shows a cOllullonly used model Il) 1 Cl l l ll 1l l J11 iCl li u ll sy --lun

-l lhough it - lIggcsls a system -or cOllllllunicaLion be1ccn t u ICllhdCh InL~I(t d

or sonar In I hich Ihe system input and output 111 1 be localed 11 Ihe 11e ie

Regardless of the particular application and conli gu-iln II 11l1l1 lmli

trallsmission systems invariably involve three lllZljor sUbSYS tlll l ~~ 11l1bIl1lIloCl Ihl

channeL and d receiver In this literature review we II I lI s lul l bmiddot I h lllkill ~ t11 LLrI1l S

01 systems ror transk r of inforlllation between rcmolch IIK ll ed poi nls II is

limited to such systellls

mes sage message

sgnat

Inp~Jt

transducer T fansmlU8r

carner

Iransmll signal

R8C81ver

addl11ve nOise Interfereflce dls tNtlon res lJolllng from ba~d limlitl119 and non Ilns-cHllls S

c u lpu t ~IJnal

OIJIPll t jrr1sJu cer

Fig 2 I Block d iagram of a communic8 tion sys lcm (Rl fc 10 Re k l llU IIII

2111 Input Transducer

The vide vanety of possible sources of informatlOn refmiddota lll S III ffi JIlV (11 1 h 1r11 1

[arms [or mess a pes Regardless of their exa c t form hOW (lr IncSS rq~~e s 1Tl1 ~

be categorized as analog or digliol The former tTl) be 1ll 1l(lt-lt- cJ s fU Il CIIlt1I 1S

of a continu ous-time variable ([or example press u re t ll n pcrdl lll4 spLrch

mus iC l whereas the latter consist of discrete symbols (for rX d rnpk 1 nlt tl

text) Almost lIwanably the message produced by a sOll rce mbl be

converted bv a transducer to a for m SUItable for til c p ltrti cul r I pe f

cnrn mU111Calion system employed For CX2lillplc 111 elre t riri11

com tT1urlicarions speech waves are converted b cl nllCiUphullf Lo nll ~e

variatIons Sucl a converted 11leSsage is referred to as 111( Incssnrlf siqnu

In thi s book therefore a signal can be Interpreted as the tmiddotu idtin l1 01 a

qua n tIty often a vOlt2gC or current with ti me

2112 Transmitter

The purpose of the transmitter is to couple the mc~sI1~ Lo Llw ~ (Inll c l

Altho ugh it is not uncommon to find the input transd u ce l dll l c lv u lu plcc1

to the trans111ission medium as for example in some interLonl s stC1l1~ iL is

often nccessary to modulate a carrier wave With the s lgn 1 flillTI tile 1111111

transducer Modulation is the systematic vanation 0 1 some illlni) u ll o f Ill

carrier such as amplitude) phase or frequency in alc nrd d l1Ce 1111

function of th e n1essage slgnal There are several reasons f(gt r 11 ing (~rncr

and modulating it Important ones are (l l for ease of ra ci lduo n 1 10 red u ce

noise and interference (3) for channel assignment (4 ) for m Ultiplex ing or

transmlssion of several messages over a single chnnnc1 ln cl (5 I f J U VL rCO ITI l

equipment limitations Several of these reasons are scJf-explanHory Olhns

such as the second ill become more mcaningfui later

In additIOn to modulation other primary functions performed by the

transmi tter a r c fil tering amplillcation and coup ling th e moct u[ed s ipnaJ tu

the channel Ifor example through an antenna or o th e r 1 pprl1 pr JIC c ( ICT I

4

PIIlt1II Ihidmftl lJaklumul H~drlUil Unl c r Sl ll Nl 1aV S1lt1 S arn~n k UNIVEllt~nl MILnSr ~~ w

2 11 3 Channel

Tl w channel can have m any different for m s the most [amil iaL pc-h p is

rh e channel that exists between tlI e transmittin g an ten n a nl ) c OlTImLrLlnl

radio s tat ion and the receivIng antenna of a rad i() 111 thi 5 ch ~ nIH1 the

transmitted slgn al propagates through the 8 trn ospllfr e Dr fn e s Pju rr t il e

receli1ng antenna Hoovever it is not uncommon to Jlnd lhl~ trlnnlI1lcr

hard-wired to the receiver as in most local te lephone syste m s Th S -hlnnl

is vastly differen t from the radio example However ~ I ~ htnncls hC1H )lIe

th ing in common the signal undergoes d egradation fn ln lld I1 S ll11 tr f 1 I

receiver Although this degradatIOn may occur at ~m POlllt or 1I

communication system block diagram lt is customan iy i1 S S~t( l ~ llC d t th lil t

channe1 alone This degrad a tion often results from nOl sc rll rl qhr r lin(lt-

on-ed signals or lIlterference but also may lIlclude o lh er (hSLO I UOll cllcLh 1S

Nell such as fad lng signallcvels multiple transIniss io n P ill-h s 8nd fillr nnf

More about these unwanted perturbatIOns will be pr esented llo lll v

2114 Receiver

The receivers fu n ction is to extract the desIred messag( lrofll Imiddothe ITr-I~ I f d

signal at the ch ill1nel output and to convert It to fUI In Sl lltlhle f lll lit

output transducer Although amplification rn3 be 11IIC or ti ll IIfb l Il

atlons per[onned by the receiver especially in radio ( ()TIl11l1nllal J1) I1 ~ ) wh(n

lhe recelved Si gn al m ay be extremely weak the rn __ ~ i ll Junc lio n uf dH r L l l I C i

is to demodula ie the received signal Oft en It IS d es ire d th lI rcCCIIl rl( output be a scaled possibly delayed version of th e mcssd gc s iYIrI I I h e

modli lator mput although in some cases a morc ge n creo l rnnclo ll I Ih e

input rnessage is desired However as a result of the p re s cll (c or nO ise d nd

distortion tlus operatIOn is less than ldeal Ways of ~pprn ] hillg Illl k11

5

case of perfec t recovery wi ll be discussed as we p roceed

211 5 Output Transducer

The outpu t transdu cer completes the communicatIOn svstem This knee

converts th e el~Ll ic s Ignal at its in pu t InLO t he f rm c1csll(d hv I he svsIt m

u ser Perh aps the m os t common OUlput tran sdu cer IS 1Iucl spIkcr

However the re ar e many oth er examples s u ch as tltlpe rccorckrs pers0I w]

computers meters and cath ode-r ay tubes an d etc

212 CHANNEL CHARACTERISTICS

Noise Sources

No ise in a co mmunica tion sys tem can be cl lsslficcl Jt1 to two 1-1 lt1

categori es depend ing on its source Noise generated bv compone nt w it hll1

a co mmunication system s u ch as resis tors eicclron lubes ii nel sol U-llI(

acti ve devices is referr ed to as internal nOise The second ca tc~nr p~l( rnal

noise r esults from sources out s ide a commul11cation system 1IIclLllthr

a tmospheri c man -m a de and extrate rrestrial sou rces

Atmospheri c noise results primarily fro m SP Uri O U S )dl n wmTS

gen erated by the n a tural e lec trical d ischarges wit llll the t111uraquoph ltl

a ssocia ted with thunderstorms It is commonly rcfc rrrd to rl S 1)11( or

spitcncs Below about 100 MHz th e fi e ld s trcl12th of such radw 1 o- S IS

in ve rsely propo rtio na l to frequen cy Almosph en c II IHSC IS Lh Ii ln IZf d 011

the time do m ai n by largeamplitude s ho rt-dura tion bu rs ls lild IS nne of t illt

p rime examples o f n oise refe rred to as trl)I)[il~I(~ RecltlIlgte of llq i The

6

dependence on frequency atmospheric nOIse 8ffcrs ( CllllnWrCIltl1 A) l

broadcast radio which occupies the frequency ra n flc fm m 550 kfl lO 110

IIHiz m ore lh an it affects television and FM rd riio wlliill 11eldle in

lreq uency bands above 50 Mhz

i1a n - l11ade noise sources include high-voltage po( rl1 n ( corona dlS shy

charge COilllllUla to r-generated nOISE In electrica l lnotors aliturT10hik d

aircran 19ni t ion nOlse and switching-gear 1l00se Ign H lon n01~e (Hid

sWltching noise like atmospheric nOIse are Imru ls ivc in c Wfa uel lmpuhc

noise is Ih e predominant type of nOIse In switched vrc ll ne c hl lllwls gt11111

as lc1cphone channels For applicatlOlls such as Olee I rdJLsnli~si o I

Imp ulse noise is only an irritation factor hovrever It can 1)( ) s~ t J(Hl~

source of error in appilC3tIons involvIng transmIssion of cl lgnal el ata

Yet another importClrlL source of man -- Tn a de noist is LHlio- fr_~ qucncy

transmitters other than the one of Interest NUJSC Ju c to 1t1lcr tc nng

transmItters is commonly referred to as radlO-freq ll l1 cy in I e reTlllC( WFII

RFI IS p anicularly troublesome In SItuations 111 ~hICh i1 I ClC IIIIL dn tcllll ll IS

su bj ect to a high -density tran smitter environrrlen L -1 S Jn rnohdc

connn unications in a large city

Extraterrestrial noise sources include oLir sun and r)t l H~r ho t

heaven lv bodIes such as stars Owing to its high t Clllpcr)tlllT (tlfill(j C) md

rebliey close proximity to the earth the sun is an Intense bUI [UIIUllattiV

localized source of radio energy that extends ovcr a broad rrr-jl1lnry

spectrum Sim ilarly the stars are sources of wlde- iJalld rClth ~ntT0middot

Although m uch more distant and hence less ink n s e Ih lI1 t i l S II Il

7

nevertheless thev are collectively an importan t source o r n Oi s e IJCT 1 1 ~( n[

their vast numbers Radio stars such as quasars ltl nci p u lsm tgt t ~lbo

In l fnSe sources u f radio energy Considered a Sig ll Zll 5r1L1n c h v n~c1ln

astrCllt Omers such stars are vieved as anolher nlnSl oour( c bv

com nlun lc atlOlls l n gIneers The frequency f clngc or ~ oln r lind ( i JSIIlI C r1l)t~ C

exlends [rom a [evil megahertz to a fevv g igltlh e r t7 - 110Ih( 1 SOU l CC 01

Interference In communication systems is m u ltiple l r d ll s m ic clt)ll pt th s

These can resull from reflection off b u il d in gs th e (]rlh rp ln IK S lJleI

ShIpS or [rom refraclion by stratifications In the lranS ITlI S lt lnn Il t dlllln If

the scattering mechanism results in numerous [(fleeted (umpH1cnls be

received multipatb signal is noiselike and is ter m ed (l i(i 5e If lil e ITlUIUI l h

slgnal componen t IS composed of only one or tVO s lTnng 11 l tT tmiddotd fnv s 11 i ~

termed specular Finally signal degradatlOl1 In a corntn LtJl1 CiJ t0l1 ~ middot ~Ll nl C 1l1

occur because of random changes in attenuallOn w ilh lll 1 h e lril llSTn is SH11l

medium Such signal perturbations (disturbances) are rde n-cd Ln CiS Ji ) )

altbou g h it should be noted that specular m u itlp 1[h abo rcs llits III l l1 rlil1 ~

due to th e constructive and destructive interferen ce uf the Fltlird IIllllLlpk

signals

Typical usesFrequency Name Microwave Band (GHz)Band

Lon rnnsc n [11gnllon snnn r3 -30k l-l z c ry low frequency

Nai gatlonai 81tb rl(ilu30-300kHz Low frequen cy

IMm l imt nl liJo cli~ t I J S~ ilL Cmiddot1 11lJ1g cliree tlJ )1l flllcling COltlsl (jlla rd (( 111 111 lPnlIHLnlal IM rltIi S c IILIl m Ic c lc

nircrnfL Cllnl il l it ll

300-3000 Medium frequ en cy

ships telcgrmiddotp il tr lepllnne anu facsimd e ~llJp- flt- C iJ ~ t

3 - 30~ll-Iz High frequen cy (I-IF

VHF t eleJ~ioJl ( lhlnnltl 5 11 radio land lrdllltpOrlllinn

30-300 Very high frequency

private GHl c raft (tll t raffic cont rol laxi C Ilgt policr navlga noTlftl ltli ds

UHF tc IILgt n l hJIllll is raclto ~() n d( 11 1 I iris

03-3 Gl-lz Ultrahigh frequency 05- 10

suncd lI1lt( r ld r sw l i ite comm 1a dio ltiml le rs

20-30 30-40 40-6 0

10-2 0

s aleii lC lIlI1 lll Jldi~ alillh lc r 1l1l Cn)~1 illk~

Superhigh freq uency 60-80 3-30GI-lL

80- 100 airborn e rlc1 ar ltlpp rnarh radar middottotile r rdciar com m on

10- 124 citrrier Inn d m ollc 30-311lt] Extremel y hig h timiddotcq Rlilroad sen icc rOldOlr Iltlding

800-40 000 Infrared (80- 400) 10Hz) ~m

40k-75k Vis ible light (40-80) ~ tn Optl c01I C() llll JlL1 n11 ti (n~

GHz S vs tCln 75000- 1O~ 1 Ultrav iolet ligh t (12-40 ~ I r

G lIz wt1lltlcnq thj

Table 22 Frequ e ncy Bands With TypIcal Uses ([dc I to Reference II))

9

In ternal nOIse resu lts from th e random motIO n o f charge ca rri- in

e lect roni c com ponen ts It can be of two general types Iderrcd to s thermal

n(js e ca u sed by the random motion of free dcc rons In crmri u or or

SClnlCO n u c tor ~xci ted by th erm al agitation and shot 110 ~dtl cd by th e

runcom arrl aJ or discre te charge carriers 111 sllrh c1e lc( as lhen rllnnLc

tubes and semicondu ctor junc tion dev ices

2 2 Baseband signal types

We a re cons idering th e s ignals only a fter they have bCI OIne ek tnmiddott 1

s Igna ls s ta rt off in non-e lectncal fo rm (eg VOIce t-m per Itun) htlt 11(

been co nve rted to vo ltage u s ing some form o f tra n sdllce Ie g mluphollr middot

thermoeoll p ie)

These e lec trical sign als form the origina l Il1for lllttioll Illch i~ 10 he middot Ilt

the baseband O nce obtai ned they III always flli Il1 ln nc 01 two i)n)d

c la sses

221 Analogue signals

In these Ihe electri cal s igna l s h ows a contmu ous vari lt1l1 Ol1 II I rtmr five r a

wide ra nge of m agni tu des Ofte n th s tim e vanatton s the e Ll h tt of

an original non-elec trical signaJ (eg au preSSlll ltI nc ( I t ~gf In

microphone) so that the two arc sa Id to be ana logou s IWllce he nme of

analogue s ignal

Digital signals

IhcOsc e lec tr ica l siglla ls consi~ ( o r d iscontinuuus pu bes (or di ~It1 elel CIIIla lll ill

duc bu ciJ ltJ ngi ng tbluptl y tiom one d igi t to the nex l I lte Ire ll SI Idl ) led

S i t~lla l s as in a ld c~ prinl e r The most common type is o f cU UJC hill~ll ( lIdinL Ih Il

List of Figures

Figure Description Page

2 1 Block d iagram of communi cation sys te m

22 0 Classes o f s ign al I I

22 1 Frequ ency Divis ion MuJti plex concept IIgt

222 Frequen cy Division Multi p lexing

(a ) FM (b)FDM (c) Baseband s pctrum lY

23 1 Basic FM Generato r 21

2 32 Im proved PM Generato r l

233 PM gen erator wilh AFC circu it 2 1

234 Block d iagram of Lim ite r r ~-

235 Diagram uf Preampli fier 26

2 36 Im provement of symmetric clippe r 27

2 3 7 Charac teri s tic of frequen cy to am pli tude H

2 38 The u se of double-tu ned circui t 30

bull 124 1 Block d iagram of domes tic recelver ~

242 Fosley Seeley Discrimina lo r 3Y

243 Diagra m of Quadrature de tec to r -to

2 4 4 Phase shift 4 1

245 Block d iagram of gtbase Locked loop 43

25 I Typicl l ifferentlal de lay H

252 Typical Amplitu de vs Frequency respon se 46

255 Probabili ty of Bit Erro r in

261 Baseband System 33

57Schem a ti c Design O [ Powered In te rcom3 0

- 1 3 1 1 Block diagram o[ in tercom system shy

4 1 0 (a ) Sch em a ti c power s upp ly

roIb) Physical -ollage regulator

6 4 1(a) Inpu t powe r s u p ply s ign a l

6 1 4 J (b) Outpu t s ignal

024 2(a ) Gate tra n s fer

142 ()) Power d iss ipa tion vs Frequ ency

42(c) S ign a l Input of inve rter 03

1)442(d) S ignal oUlput of inverte r

(54 3 (a ) S ign al mput of lone decode r

fgt)4 3 ()) S ign al of ca pac itor timin g

6r43(c) S ignal of resistor tim ing

Uh43 (c) S ign al [ter through 2 K res is to r

(I4 3 (e) S ig11 a l after throu gh 2 2 K resisto r

h7 Signal after thro ugh 27 K res is tor 43(f)

(g43(g) Outp u t of tone decod er

6944 I(a) Inpu t (+) of ampli fie r

4 4 lib) In pu t ( ) of ampli fi er I))

44 I (e) Ou tput Sign al of a mplifie r 70

70 44 fel) VolLage source of amplifi er

4 5 Sys te m ou tput s ignal 7

List Of Tables

Table Dcscript Ion

9Frequency band21

12 22 1 Types of Baseband Signal

253 Requirement fo r two or mUltipoint 46

254 Requirem ent for two or multJ point for

47Envelope del ay distortion

Chapter 1

Introduction of Powered Intercom Project

Introduction

A vast n e twork telecommunicatIOn llllks spans tltc in duS Trilaquolt zcd

COU ntne of the world carrymg telephone te legraph tclcvi ion n e5

p h ologra phs a nd ra dio programs ThIS n e twork IS con stro n llv heing

exp a nded a nd n ew invention s are increasin g its capaCIty ltIt breathtnllt lI1g

ra te The re were m any proble ms we have en cou ntered in th e bq~i l I inf( bu t

s lowly soluti on s have been found We have learn ed to li se the IlI1 llts m o re

e ffi c ie ntly a nd th e cos ts have dropped dramatIc a lly Nowodays there ltIre

m a n y typ es of links that has been use d to com mUI1lCCllr an ti Ilslng the

power su pply to co mmunicate is a new method

Inter com technology has been found 111 ea rlv 1 9~) Os ami s lowl It s

b een expanded to be used in local area network nor WIde lea network

Powered inter com is a new technology where It is slmi l r to lIinkss

intercom However wlreless lntercom IS a system there ~() Ineo n e C(Ul

communicate w1th each other 111 the same small a r ea (h ousr n bllil cll llg)

without using wire d links but for powered intcrcnm SOIneon e ju s t need to

plu g it to th e power supply without worryll1g on h ow to lin k the Inl r](om

By u s ing thi s techno logy it is more con venien t for the c u stomer tu put the

in tercom system s w ith ou t worrym g how to Ill s t ltl ll (mess) w lr(d) and n1lll(

o rganized Neve rtheless a lot o f problems to imple m ent this 1lt11lc o f

sys te m s

For th IS thesis the c haracteris tics on th~ powtrn ml errC)m ~11 1 hI

s tudied befo re Implement the product Neve rth eless thi S repo rt is Iso

s tudy case all the advan ced of telecommuI1Ication s

Chapter 2

Literature Review of Powered Intercom Project

21 WHAT IS COMMUNICATION

211 THE BLOCK DIAGRAM OF A COMMUNICATION SYSTEM

Fi gure 20 shows a cOllullonly used model Il) 1 Cl l l ll 1l l J11 iCl li u ll sy --lun

-l lhough it - lIggcsls a system -or cOllllllunicaLion be1ccn t u ICllhdCh InL~I(t d

or sonar In I hich Ihe system input and output 111 1 be localed 11 Ihe 11e ie

Regardless of the particular application and conli gu-iln II 11l1l1 lmli

trallsmission systems invariably involve three lllZljor sUbSYS tlll l ~~ 11l1bIl1lIloCl Ihl

channeL and d receiver In this literature review we II I lI s lul l bmiddot I h lllkill ~ t11 LLrI1l S

01 systems ror transk r of inforlllation between rcmolch IIK ll ed poi nls II is

limited to such systellls

mes sage message

sgnat

Inp~Jt

transducer T fansmlU8r

carner

Iransmll signal

R8C81ver

addl11ve nOise Interfereflce dls tNtlon res lJolllng from ba~d limlitl119 and non Ilns-cHllls S

c u lpu t ~IJnal

OIJIPll t jrr1sJu cer

Fig 2 I Block d iagram of a communic8 tion sys lcm (Rl fc 10 Re k l llU IIII

2111 Input Transducer

The vide vanety of possible sources of informatlOn refmiddota lll S III ffi JIlV (11 1 h 1r11 1

[arms [or mess a pes Regardless of their exa c t form hOW (lr IncSS rq~~e s 1Tl1 ~

be categorized as analog or digliol The former tTl) be 1ll 1l(lt-lt- cJ s fU Il CIIlt1I 1S

of a continu ous-time variable ([or example press u re t ll n pcrdl lll4 spLrch

mus iC l whereas the latter consist of discrete symbols (for rX d rnpk 1 nlt tl

text) Almost lIwanably the message produced by a sOll rce mbl be

converted bv a transducer to a for m SUItable for til c p ltrti cul r I pe f

cnrn mU111Calion system employed For CX2lillplc 111 elre t riri11

com tT1urlicarions speech waves are converted b cl nllCiUphullf Lo nll ~e

variatIons Sucl a converted 11leSsage is referred to as 111( Incssnrlf siqnu

In thi s book therefore a signal can be Interpreted as the tmiddotu idtin l1 01 a

qua n tIty often a vOlt2gC or current with ti me

2112 Transmitter

The purpose of the transmitter is to couple the mc~sI1~ Lo Llw ~ (Inll c l

Altho ugh it is not uncommon to find the input transd u ce l dll l c lv u lu plcc1

to the trans111ission medium as for example in some interLonl s stC1l1~ iL is

often nccessary to modulate a carrier wave With the s lgn 1 flillTI tile 1111111

transducer Modulation is the systematic vanation 0 1 some illlni) u ll o f Ill

carrier such as amplitude) phase or frequency in alc nrd d l1Ce 1111

function of th e n1essage slgnal There are several reasons f(gt r 11 ing (~rncr

and modulating it Important ones are (l l for ease of ra ci lduo n 1 10 red u ce

noise and interference (3) for channel assignment (4 ) for m Ultiplex ing or

transmlssion of several messages over a single chnnnc1 ln cl (5 I f J U VL rCO ITI l

equipment limitations Several of these reasons are scJf-explanHory Olhns

such as the second ill become more mcaningfui later

In additIOn to modulation other primary functions performed by the

transmi tter a r c fil tering amplillcation and coup ling th e moct u[ed s ipnaJ tu

the channel Ifor example through an antenna or o th e r 1 pprl1 pr JIC c ( ICT I

4

PIIlt1II Ihidmftl lJaklumul H~drlUil Unl c r Sl ll Nl 1aV S1lt1 S arn~n k UNIVEllt~nl MILnSr ~~ w

2 11 3 Channel

Tl w channel can have m any different for m s the most [amil iaL pc-h p is

rh e channel that exists between tlI e transmittin g an ten n a nl ) c OlTImLrLlnl

radio s tat ion and the receivIng antenna of a rad i() 111 thi 5 ch ~ nIH1 the

transmitted slgn al propagates through the 8 trn ospllfr e Dr fn e s Pju rr t il e

receli1ng antenna Hoovever it is not uncommon to Jlnd lhl~ trlnnlI1lcr

hard-wired to the receiver as in most local te lephone syste m s Th S -hlnnl

is vastly differen t from the radio example However ~ I ~ htnncls hC1H )lIe

th ing in common the signal undergoes d egradation fn ln lld I1 S ll11 tr f 1 I

receiver Although this degradatIOn may occur at ~m POlllt or 1I

communication system block diagram lt is customan iy i1 S S~t( l ~ llC d t th lil t

channe1 alone This degrad a tion often results from nOl sc rll rl qhr r lin(lt-

on-ed signals or lIlterference but also may lIlclude o lh er (hSLO I UOll cllcLh 1S

Nell such as fad lng signallcvels multiple transIniss io n P ill-h s 8nd fillr nnf

More about these unwanted perturbatIOns will be pr esented llo lll v

2114 Receiver

The receivers fu n ction is to extract the desIred messag( lrofll Imiddothe ITr-I~ I f d

signal at the ch ill1nel output and to convert It to fUI In Sl lltlhle f lll lit

output transducer Although amplification rn3 be 11IIC or ti ll IIfb l Il

atlons per[onned by the receiver especially in radio ( ()TIl11l1nllal J1) I1 ~ ) wh(n

lhe recelved Si gn al m ay be extremely weak the rn __ ~ i ll Junc lio n uf dH r L l l I C i

is to demodula ie the received signal Oft en It IS d es ire d th lI rcCCIIl rl( output be a scaled possibly delayed version of th e mcssd gc s iYIrI I I h e

modli lator mput although in some cases a morc ge n creo l rnnclo ll I Ih e

input rnessage is desired However as a result of the p re s cll (c or nO ise d nd

distortion tlus operatIOn is less than ldeal Ways of ~pprn ] hillg Illl k11

5

case of perfec t recovery wi ll be discussed as we p roceed

211 5 Output Transducer

The outpu t transdu cer completes the communicatIOn svstem This knee

converts th e el~Ll ic s Ignal at its in pu t InLO t he f rm c1csll(d hv I he svsIt m

u ser Perh aps the m os t common OUlput tran sdu cer IS 1Iucl spIkcr

However the re ar e many oth er examples s u ch as tltlpe rccorckrs pers0I w]

computers meters and cath ode-r ay tubes an d etc

212 CHANNEL CHARACTERISTICS

Noise Sources

No ise in a co mmunica tion sys tem can be cl lsslficcl Jt1 to two 1-1 lt1

categori es depend ing on its source Noise generated bv compone nt w it hll1

a co mmunication system s u ch as resis tors eicclron lubes ii nel sol U-llI(

acti ve devices is referr ed to as internal nOise The second ca tc~nr p~l( rnal

noise r esults from sources out s ide a commul11cation system 1IIclLllthr

a tmospheri c man -m a de and extrate rrestrial sou rces

Atmospheri c noise results primarily fro m SP Uri O U S )dl n wmTS

gen erated by the n a tural e lec trical d ischarges wit llll the t111uraquoph ltl

a ssocia ted with thunderstorms It is commonly rcfc rrrd to rl S 1)11( or

spitcncs Below about 100 MHz th e fi e ld s trcl12th of such radw 1 o- S IS

in ve rsely propo rtio na l to frequen cy Almosph en c II IHSC IS Lh Ii ln IZf d 011

the time do m ai n by largeamplitude s ho rt-dura tion bu rs ls lild IS nne of t illt

p rime examples o f n oise refe rred to as trl)I)[il~I(~ RecltlIlgte of llq i The

6

dependence on frequency atmospheric nOIse 8ffcrs ( CllllnWrCIltl1 A) l

broadcast radio which occupies the frequency ra n flc fm m 550 kfl lO 110

IIHiz m ore lh an it affects television and FM rd riio wlliill 11eldle in

lreq uency bands above 50 Mhz

i1a n - l11ade noise sources include high-voltage po( rl1 n ( corona dlS shy

charge COilllllUla to r-generated nOISE In electrica l lnotors aliturT10hik d

aircran 19ni t ion nOlse and switching-gear 1l00se Ign H lon n01~e (Hid

sWltching noise like atmospheric nOIse are Imru ls ivc in c Wfa uel lmpuhc

noise is Ih e predominant type of nOIse In switched vrc ll ne c hl lllwls gt11111

as lc1cphone channels For applicatlOlls such as Olee I rdJLsnli~si o I

Imp ulse noise is only an irritation factor hovrever It can 1)( ) s~ t J(Hl~

source of error in appilC3tIons involvIng transmIssion of cl lgnal el ata

Yet another importClrlL source of man -- Tn a de noist is LHlio- fr_~ qucncy

transmitters other than the one of Interest NUJSC Ju c to 1t1lcr tc nng

transmItters is commonly referred to as radlO-freq ll l1 cy in I e reTlllC( WFII

RFI IS p anicularly troublesome In SItuations 111 ~hICh i1 I ClC IIIIL dn tcllll ll IS

su bj ect to a high -density tran smitter environrrlen L -1 S Jn rnohdc

connn unications in a large city

Extraterrestrial noise sources include oLir sun and r)t l H~r ho t

heaven lv bodIes such as stars Owing to its high t Clllpcr)tlllT (tlfill(j C) md

rebliey close proximity to the earth the sun is an Intense bUI [UIIUllattiV

localized source of radio energy that extends ovcr a broad rrr-jl1lnry

spectrum Sim ilarly the stars are sources of wlde- iJalld rClth ~ntT0middot

Although m uch more distant and hence less ink n s e Ih lI1 t i l S II Il

7

nevertheless thev are collectively an importan t source o r n Oi s e IJCT 1 1 ~( n[

their vast numbers Radio stars such as quasars ltl nci p u lsm tgt t ~lbo

In l fnSe sources u f radio energy Considered a Sig ll Zll 5r1L1n c h v n~c1ln

astrCllt Omers such stars are vieved as anolher nlnSl oour( c bv

com nlun lc atlOlls l n gIneers The frequency f clngc or ~ oln r lind ( i JSIIlI C r1l)t~ C

exlends [rom a [evil megahertz to a fevv g igltlh e r t7 - 110Ih( 1 SOU l CC 01

Interference In communication systems is m u ltiple l r d ll s m ic clt)ll pt th s

These can resull from reflection off b u il d in gs th e (]rlh rp ln IK S lJleI

ShIpS or [rom refraclion by stratifications In the lranS ITlI S lt lnn Il t dlllln If

the scattering mechanism results in numerous [(fleeted (umpH1cnls be

received multipatb signal is noiselike and is ter m ed (l i(i 5e If lil e ITlUIUI l h

slgnal componen t IS composed of only one or tVO s lTnng 11 l tT tmiddotd fnv s 11 i ~

termed specular Finally signal degradatlOl1 In a corntn LtJl1 CiJ t0l1 ~ middot ~Ll nl C 1l1

occur because of random changes in attenuallOn w ilh lll 1 h e lril llSTn is SH11l

medium Such signal perturbations (disturbances) are rde n-cd Ln CiS Ji ) )

altbou g h it should be noted that specular m u itlp 1[h abo rcs llits III l l1 rlil1 ~

due to th e constructive and destructive interferen ce uf the Fltlird IIllllLlpk

signals

Typical usesFrequency Name Microwave Band (GHz)Band

Lon rnnsc n [11gnllon snnn r3 -30k l-l z c ry low frequency

Nai gatlonai 81tb rl(ilu30-300kHz Low frequen cy

IMm l imt nl liJo cli~ t I J S~ ilL Cmiddot1 11lJ1g cliree tlJ )1l flllcling COltlsl (jlla rd (( 111 111 lPnlIHLnlal IM rltIi S c IILIl m Ic c lc

nircrnfL Cllnl il l it ll

300-3000 Medium frequ en cy

ships telcgrmiddotp il tr lepllnne anu facsimd e ~llJp- flt- C iJ ~ t

3 - 30~ll-Iz High frequen cy (I-IF

VHF t eleJ~ioJl ( lhlnnltl 5 11 radio land lrdllltpOrlllinn

30-300 Very high frequency

private GHl c raft (tll t raffic cont rol laxi C Ilgt policr navlga noTlftl ltli ds

UHF tc IILgt n l hJIllll is raclto ~() n d( 11 1 I iris

03-3 Gl-lz Ultrahigh frequency 05- 10

suncd lI1lt( r ld r sw l i ite comm 1a dio ltiml le rs

20-30 30-40 40-6 0

10-2 0

s aleii lC lIlI1 lll Jldi~ alillh lc r 1l1l Cn)~1 illk~

Superhigh freq uency 60-80 3-30GI-lL

80- 100 airborn e rlc1 ar ltlpp rnarh radar middottotile r rdciar com m on

10- 124 citrrier Inn d m ollc 30-311lt] Extremel y hig h timiddotcq Rlilroad sen icc rOldOlr Iltlding

800-40 000 Infrared (80- 400) 10Hz) ~m

40k-75k Vis ible light (40-80) ~ tn Optl c01I C() llll JlL1 n11 ti (n~

GHz S vs tCln 75000- 1O~ 1 Ultrav iolet ligh t (12-40 ~ I r

G lIz wt1lltlcnq thj

Table 22 Frequ e ncy Bands With TypIcal Uses ([dc I to Reference II))

9

In ternal nOIse resu lts from th e random motIO n o f charge ca rri- in

e lect roni c com ponen ts It can be of two general types Iderrcd to s thermal

n(js e ca u sed by the random motion of free dcc rons In crmri u or or

SClnlCO n u c tor ~xci ted by th erm al agitation and shot 110 ~dtl cd by th e

runcom arrl aJ or discre te charge carriers 111 sllrh c1e lc( as lhen rllnnLc

tubes and semicondu ctor junc tion dev ices

2 2 Baseband signal types

We a re cons idering th e s ignals only a fter they have bCI OIne ek tnmiddott 1

s Igna ls s ta rt off in non-e lectncal fo rm (eg VOIce t-m per Itun) htlt 11(

been co nve rted to vo ltage u s ing some form o f tra n sdllce Ie g mluphollr middot

thermoeoll p ie)

These e lec trical sign als form the origina l Il1for lllttioll Illch i~ 10 he middot Ilt

the baseband O nce obtai ned they III always flli Il1 ln nc 01 two i)n)d

c la sses

221 Analogue signals

In these Ihe electri cal s igna l s h ows a contmu ous vari lt1l1 Ol1 II I rtmr five r a

wide ra nge of m agni tu des Ofte n th s tim e vanatton s the e Ll h tt of

an original non-elec trical signaJ (eg au preSSlll ltI nc ( I t ~gf In

microphone) so that the two arc sa Id to be ana logou s IWllce he nme of

analogue s ignal

Digital signals

IhcOsc e lec tr ica l siglla ls consi~ ( o r d iscontinuuus pu bes (or di ~It1 elel CIIIla lll ill

duc bu ciJ ltJ ngi ng tbluptl y tiom one d igi t to the nex l I lte Ire ll SI Idl ) led

S i t~lla l s as in a ld c~ prinl e r The most common type is o f cU UJC hill~ll ( lIdinL Ih Il

57Schem a ti c Design O [ Powered In te rcom3 0

- 1 3 1 1 Block diagram o[ in tercom system shy

4 1 0 (a ) Sch em a ti c power s upp ly

roIb) Physical -ollage regulator

6 4 1(a) Inpu t powe r s u p ply s ign a l

6 1 4 J (b) Outpu t s ignal

024 2(a ) Gate tra n s fer

142 ()) Power d iss ipa tion vs Frequ ency

42(c) S ign a l Input of inve rter 03

1)442(d) S ignal oUlput of inverte r

(54 3 (a ) S ign al mput of lone decode r

fgt)4 3 ()) S ign al of ca pac itor timin g

6r43(c) S ignal of resistor tim ing

Uh43 (c) S ign al [ter through 2 K res is to r

(I4 3 (e) S ig11 a l after throu gh 2 2 K resisto r

h7 Signal after thro ugh 27 K res is tor 43(f)

(g43(g) Outp u t of tone decod er

6944 I(a) Inpu t (+) of ampli fie r

4 4 lib) In pu t ( ) of ampli fi er I))

44 I (e) Ou tput Sign al of a mplifie r 70

70 44 fel) VolLage source of amplifi er

4 5 Sys te m ou tput s ignal 7

List Of Tables

Table Dcscript Ion

9Frequency band21

12 22 1 Types of Baseband Signal

253 Requirement fo r two or mUltipoint 46

254 Requirem ent for two or multJ point for

47Envelope del ay distortion

Chapter 1

Introduction of Powered Intercom Project

Introduction

A vast n e twork telecommunicatIOn llllks spans tltc in duS Trilaquolt zcd

COU ntne of the world carrymg telephone te legraph tclcvi ion n e5

p h ologra phs a nd ra dio programs ThIS n e twork IS con stro n llv heing

exp a nded a nd n ew invention s are increasin g its capaCIty ltIt breathtnllt lI1g

ra te The re were m any proble ms we have en cou ntered in th e bq~i l I inf( bu t

s lowly soluti on s have been found We have learn ed to li se the IlI1 llts m o re

e ffi c ie ntly a nd th e cos ts have dropped dramatIc a lly Nowodays there ltIre

m a n y typ es of links that has been use d to com mUI1lCCllr an ti Ilslng the

power su pply to co mmunicate is a new method

Inter com technology has been found 111 ea rlv 1 9~) Os ami s lowl It s

b een expanded to be used in local area network nor WIde lea network

Powered inter com is a new technology where It is slmi l r to lIinkss

intercom However wlreless lntercom IS a system there ~() Ineo n e C(Ul

communicate w1th each other 111 the same small a r ea (h ousr n bllil cll llg)

without using wire d links but for powered intcrcnm SOIneon e ju s t need to

plu g it to th e power supply without worryll1g on h ow to lin k the Inl r](om

By u s ing thi s techno logy it is more con venien t for the c u stomer tu put the

in tercom system s w ith ou t worrym g how to Ill s t ltl ll (mess) w lr(d) and n1lll(

o rganized Neve rtheless a lot o f problems to imple m ent this 1lt11lc o f

sys te m s

For th IS thesis the c haracteris tics on th~ powtrn ml errC)m ~11 1 hI

s tudied befo re Implement the product Neve rth eless thi S repo rt is Iso

s tudy case all the advan ced of telecommuI1Ication s

Chapter 2

Literature Review of Powered Intercom Project

21 WHAT IS COMMUNICATION

211 THE BLOCK DIAGRAM OF A COMMUNICATION SYSTEM

Fi gure 20 shows a cOllullonly used model Il) 1 Cl l l ll 1l l J11 iCl li u ll sy --lun

-l lhough it - lIggcsls a system -or cOllllllunicaLion be1ccn t u ICllhdCh InL~I(t d

or sonar In I hich Ihe system input and output 111 1 be localed 11 Ihe 11e ie

Regardless of the particular application and conli gu-iln II 11l1l1 lmli

trallsmission systems invariably involve three lllZljor sUbSYS tlll l ~~ 11l1bIl1lIloCl Ihl

channeL and d receiver In this literature review we II I lI s lul l bmiddot I h lllkill ~ t11 LLrI1l S

01 systems ror transk r of inforlllation between rcmolch IIK ll ed poi nls II is

limited to such systellls

mes sage message

sgnat

Inp~Jt

transducer T fansmlU8r

carner

Iransmll signal

R8C81ver

addl11ve nOise Interfereflce dls tNtlon res lJolllng from ba~d limlitl119 and non Ilns-cHllls S

c u lpu t ~IJnal

OIJIPll t jrr1sJu cer

Fig 2 I Block d iagram of a communic8 tion sys lcm (Rl fc 10 Re k l llU IIII

2111 Input Transducer

The vide vanety of possible sources of informatlOn refmiddota lll S III ffi JIlV (11 1 h 1r11 1

[arms [or mess a pes Regardless of their exa c t form hOW (lr IncSS rq~~e s 1Tl1 ~

be categorized as analog or digliol The former tTl) be 1ll 1l(lt-lt- cJ s fU Il CIIlt1I 1S

of a continu ous-time variable ([or example press u re t ll n pcrdl lll4 spLrch

mus iC l whereas the latter consist of discrete symbols (for rX d rnpk 1 nlt tl

text) Almost lIwanably the message produced by a sOll rce mbl be

converted bv a transducer to a for m SUItable for til c p ltrti cul r I pe f

cnrn mU111Calion system employed For CX2lillplc 111 elre t riri11

com tT1urlicarions speech waves are converted b cl nllCiUphullf Lo nll ~e

variatIons Sucl a converted 11leSsage is referred to as 111( Incssnrlf siqnu

In thi s book therefore a signal can be Interpreted as the tmiddotu idtin l1 01 a

qua n tIty often a vOlt2gC or current with ti me

2112 Transmitter

The purpose of the transmitter is to couple the mc~sI1~ Lo Llw ~ (Inll c l

Altho ugh it is not uncommon to find the input transd u ce l dll l c lv u lu plcc1

to the trans111ission medium as for example in some interLonl s stC1l1~ iL is

often nccessary to modulate a carrier wave With the s lgn 1 flillTI tile 1111111

transducer Modulation is the systematic vanation 0 1 some illlni) u ll o f Ill

carrier such as amplitude) phase or frequency in alc nrd d l1Ce 1111

function of th e n1essage slgnal There are several reasons f(gt r 11 ing (~rncr

and modulating it Important ones are (l l for ease of ra ci lduo n 1 10 red u ce

noise and interference (3) for channel assignment (4 ) for m Ultiplex ing or

transmlssion of several messages over a single chnnnc1 ln cl (5 I f J U VL rCO ITI l

equipment limitations Several of these reasons are scJf-explanHory Olhns

such as the second ill become more mcaningfui later

In additIOn to modulation other primary functions performed by the

transmi tter a r c fil tering amplillcation and coup ling th e moct u[ed s ipnaJ tu

the channel Ifor example through an antenna or o th e r 1 pprl1 pr JIC c ( ICT I

4

PIIlt1II Ihidmftl lJaklumul H~drlUil Unl c r Sl ll Nl 1aV S1lt1 S arn~n k UNIVEllt~nl MILnSr ~~ w

2 11 3 Channel

Tl w channel can have m any different for m s the most [amil iaL pc-h p is

rh e channel that exists between tlI e transmittin g an ten n a nl ) c OlTImLrLlnl

radio s tat ion and the receivIng antenna of a rad i() 111 thi 5 ch ~ nIH1 the

transmitted slgn al propagates through the 8 trn ospllfr e Dr fn e s Pju rr t il e

receli1ng antenna Hoovever it is not uncommon to Jlnd lhl~ trlnnlI1lcr

hard-wired to the receiver as in most local te lephone syste m s Th S -hlnnl

is vastly differen t from the radio example However ~ I ~ htnncls hC1H )lIe

th ing in common the signal undergoes d egradation fn ln lld I1 S ll11 tr f 1 I

receiver Although this degradatIOn may occur at ~m POlllt or 1I

communication system block diagram lt is customan iy i1 S S~t( l ~ llC d t th lil t

channe1 alone This degrad a tion often results from nOl sc rll rl qhr r lin(lt-

on-ed signals or lIlterference but also may lIlclude o lh er (hSLO I UOll cllcLh 1S

Nell such as fad lng signallcvels multiple transIniss io n P ill-h s 8nd fillr nnf

More about these unwanted perturbatIOns will be pr esented llo lll v

2114 Receiver

The receivers fu n ction is to extract the desIred messag( lrofll Imiddothe ITr-I~ I f d

signal at the ch ill1nel output and to convert It to fUI In Sl lltlhle f lll lit

output transducer Although amplification rn3 be 11IIC or ti ll IIfb l Il

atlons per[onned by the receiver especially in radio ( ()TIl11l1nllal J1) I1 ~ ) wh(n

lhe recelved Si gn al m ay be extremely weak the rn __ ~ i ll Junc lio n uf dH r L l l I C i

is to demodula ie the received signal Oft en It IS d es ire d th lI rcCCIIl rl( output be a scaled possibly delayed version of th e mcssd gc s iYIrI I I h e

modli lator mput although in some cases a morc ge n creo l rnnclo ll I Ih e

input rnessage is desired However as a result of the p re s cll (c or nO ise d nd

distortion tlus operatIOn is less than ldeal Ways of ~pprn ] hillg Illl k11

5

case of perfec t recovery wi ll be discussed as we p roceed

211 5 Output Transducer

The outpu t transdu cer completes the communicatIOn svstem This knee

converts th e el~Ll ic s Ignal at its in pu t InLO t he f rm c1csll(d hv I he svsIt m

u ser Perh aps the m os t common OUlput tran sdu cer IS 1Iucl spIkcr

However the re ar e many oth er examples s u ch as tltlpe rccorckrs pers0I w]

computers meters and cath ode-r ay tubes an d etc

212 CHANNEL CHARACTERISTICS

Noise Sources

No ise in a co mmunica tion sys tem can be cl lsslficcl Jt1 to two 1-1 lt1

categori es depend ing on its source Noise generated bv compone nt w it hll1

a co mmunication system s u ch as resis tors eicclron lubes ii nel sol U-llI(

acti ve devices is referr ed to as internal nOise The second ca tc~nr p~l( rnal

noise r esults from sources out s ide a commul11cation system 1IIclLllthr

a tmospheri c man -m a de and extrate rrestrial sou rces

Atmospheri c noise results primarily fro m SP Uri O U S )dl n wmTS

gen erated by the n a tural e lec trical d ischarges wit llll the t111uraquoph ltl

a ssocia ted with thunderstorms It is commonly rcfc rrrd to rl S 1)11( or

spitcncs Below about 100 MHz th e fi e ld s trcl12th of such radw 1 o- S IS

in ve rsely propo rtio na l to frequen cy Almosph en c II IHSC IS Lh Ii ln IZf d 011

the time do m ai n by largeamplitude s ho rt-dura tion bu rs ls lild IS nne of t illt

p rime examples o f n oise refe rred to as trl)I)[il~I(~ RecltlIlgte of llq i The

6

dependence on frequency atmospheric nOIse 8ffcrs ( CllllnWrCIltl1 A) l

broadcast radio which occupies the frequency ra n flc fm m 550 kfl lO 110

IIHiz m ore lh an it affects television and FM rd riio wlliill 11eldle in

lreq uency bands above 50 Mhz

i1a n - l11ade noise sources include high-voltage po( rl1 n ( corona dlS shy

charge COilllllUla to r-generated nOISE In electrica l lnotors aliturT10hik d

aircran 19ni t ion nOlse and switching-gear 1l00se Ign H lon n01~e (Hid

sWltching noise like atmospheric nOIse are Imru ls ivc in c Wfa uel lmpuhc

noise is Ih e predominant type of nOIse In switched vrc ll ne c hl lllwls gt11111

as lc1cphone channels For applicatlOlls such as Olee I rdJLsnli~si o I

Imp ulse noise is only an irritation factor hovrever It can 1)( ) s~ t J(Hl~

source of error in appilC3tIons involvIng transmIssion of cl lgnal el ata

Yet another importClrlL source of man -- Tn a de noist is LHlio- fr_~ qucncy

transmitters other than the one of Interest NUJSC Ju c to 1t1lcr tc nng

transmItters is commonly referred to as radlO-freq ll l1 cy in I e reTlllC( WFII

RFI IS p anicularly troublesome In SItuations 111 ~hICh i1 I ClC IIIIL dn tcllll ll IS

su bj ect to a high -density tran smitter environrrlen L -1 S Jn rnohdc

connn unications in a large city

Extraterrestrial noise sources include oLir sun and r)t l H~r ho t

heaven lv bodIes such as stars Owing to its high t Clllpcr)tlllT (tlfill(j C) md

rebliey close proximity to the earth the sun is an Intense bUI [UIIUllattiV

localized source of radio energy that extends ovcr a broad rrr-jl1lnry

spectrum Sim ilarly the stars are sources of wlde- iJalld rClth ~ntT0middot

Although m uch more distant and hence less ink n s e Ih lI1 t i l S II Il

7

nevertheless thev are collectively an importan t source o r n Oi s e IJCT 1 1 ~( n[

their vast numbers Radio stars such as quasars ltl nci p u lsm tgt t ~lbo

In l fnSe sources u f radio energy Considered a Sig ll Zll 5r1L1n c h v n~c1ln

astrCllt Omers such stars are vieved as anolher nlnSl oour( c bv

com nlun lc atlOlls l n gIneers The frequency f clngc or ~ oln r lind ( i JSIIlI C r1l)t~ C

exlends [rom a [evil megahertz to a fevv g igltlh e r t7 - 110Ih( 1 SOU l CC 01

Interference In communication systems is m u ltiple l r d ll s m ic clt)ll pt th s

These can resull from reflection off b u il d in gs th e (]rlh rp ln IK S lJleI

ShIpS or [rom refraclion by stratifications In the lranS ITlI S lt lnn Il t dlllln If

the scattering mechanism results in numerous [(fleeted (umpH1cnls be

received multipatb signal is noiselike and is ter m ed (l i(i 5e If lil e ITlUIUI l h

slgnal componen t IS composed of only one or tVO s lTnng 11 l tT tmiddotd fnv s 11 i ~

termed specular Finally signal degradatlOl1 In a corntn LtJl1 CiJ t0l1 ~ middot ~Ll nl C 1l1

occur because of random changes in attenuallOn w ilh lll 1 h e lril llSTn is SH11l

medium Such signal perturbations (disturbances) are rde n-cd Ln CiS Ji ) )

altbou g h it should be noted that specular m u itlp 1[h abo rcs llits III l l1 rlil1 ~

due to th e constructive and destructive interferen ce uf the Fltlird IIllllLlpk

signals

Typical usesFrequency Name Microwave Band (GHz)Band

Lon rnnsc n [11gnllon snnn r3 -30k l-l z c ry low frequency

Nai gatlonai 81tb rl(ilu30-300kHz Low frequen cy

IMm l imt nl liJo cli~ t I J S~ ilL Cmiddot1 11lJ1g cliree tlJ )1l flllcling COltlsl (jlla rd (( 111 111 lPnlIHLnlal IM rltIi S c IILIl m Ic c lc

nircrnfL Cllnl il l it ll

300-3000 Medium frequ en cy

ships telcgrmiddotp il tr lepllnne anu facsimd e ~llJp- flt- C iJ ~ t

3 - 30~ll-Iz High frequen cy (I-IF

VHF t eleJ~ioJl ( lhlnnltl 5 11 radio land lrdllltpOrlllinn

30-300 Very high frequency

private GHl c raft (tll t raffic cont rol laxi C Ilgt policr navlga noTlftl ltli ds

UHF tc IILgt n l hJIllll is raclto ~() n d( 11 1 I iris

03-3 Gl-lz Ultrahigh frequency 05- 10

suncd lI1lt( r ld r sw l i ite comm 1a dio ltiml le rs

20-30 30-40 40-6 0

10-2 0

s aleii lC lIlI1 lll Jldi~ alillh lc r 1l1l Cn)~1 illk~

Superhigh freq uency 60-80 3-30GI-lL

80- 100 airborn e rlc1 ar ltlpp rnarh radar middottotile r rdciar com m on

10- 124 citrrier Inn d m ollc 30-311lt] Extremel y hig h timiddotcq Rlilroad sen icc rOldOlr Iltlding

800-40 000 Infrared (80- 400) 10Hz) ~m

40k-75k Vis ible light (40-80) ~ tn Optl c01I C() llll JlL1 n11 ti (n~

GHz S vs tCln 75000- 1O~ 1 Ultrav iolet ligh t (12-40 ~ I r

G lIz wt1lltlcnq thj

Table 22 Frequ e ncy Bands With TypIcal Uses ([dc I to Reference II))

9

In ternal nOIse resu lts from th e random motIO n o f charge ca rri- in

e lect roni c com ponen ts It can be of two general types Iderrcd to s thermal

n(js e ca u sed by the random motion of free dcc rons In crmri u or or

SClnlCO n u c tor ~xci ted by th erm al agitation and shot 110 ~dtl cd by th e

runcom arrl aJ or discre te charge carriers 111 sllrh c1e lc( as lhen rllnnLc

tubes and semicondu ctor junc tion dev ices

2 2 Baseband signal types

We a re cons idering th e s ignals only a fter they have bCI OIne ek tnmiddott 1

s Igna ls s ta rt off in non-e lectncal fo rm (eg VOIce t-m per Itun) htlt 11(

been co nve rted to vo ltage u s ing some form o f tra n sdllce Ie g mluphollr middot

thermoeoll p ie)

These e lec trical sign als form the origina l Il1for lllttioll Illch i~ 10 he middot Ilt

the baseband O nce obtai ned they III always flli Il1 ln nc 01 two i)n)d

c la sses

221 Analogue signals

In these Ihe electri cal s igna l s h ows a contmu ous vari lt1l1 Ol1 II I rtmr five r a

wide ra nge of m agni tu des Ofte n th s tim e vanatton s the e Ll h tt of

an original non-elec trical signaJ (eg au preSSlll ltI nc ( I t ~gf In

microphone) so that the two arc sa Id to be ana logou s IWllce he nme of

analogue s ignal

Digital signals

IhcOsc e lec tr ica l siglla ls consi~ ( o r d iscontinuuus pu bes (or di ~It1 elel CIIIla lll ill

duc bu ciJ ltJ ngi ng tbluptl y tiom one d igi t to the nex l I lte Ire ll SI Idl ) led

S i t~lla l s as in a ld c~ prinl e r The most common type is o f cU UJC hill~ll ( lIdinL Ih Il

List Of Tables

Table Dcscript Ion

9Frequency band21

12 22 1 Types of Baseband Signal

253 Requirement fo r two or mUltipoint 46

254 Requirem ent for two or multJ point for

47Envelope del ay distortion

Chapter 1

Introduction of Powered Intercom Project

Introduction

A vast n e twork telecommunicatIOn llllks spans tltc in duS Trilaquolt zcd

COU ntne of the world carrymg telephone te legraph tclcvi ion n e5

p h ologra phs a nd ra dio programs ThIS n e twork IS con stro n llv heing

exp a nded a nd n ew invention s are increasin g its capaCIty ltIt breathtnllt lI1g

ra te The re were m any proble ms we have en cou ntered in th e bq~i l I inf( bu t

s lowly soluti on s have been found We have learn ed to li se the IlI1 llts m o re

e ffi c ie ntly a nd th e cos ts have dropped dramatIc a lly Nowodays there ltIre

m a n y typ es of links that has been use d to com mUI1lCCllr an ti Ilslng the

power su pply to co mmunicate is a new method

Inter com technology has been found 111 ea rlv 1 9~) Os ami s lowl It s

b een expanded to be used in local area network nor WIde lea network

Powered inter com is a new technology where It is slmi l r to lIinkss

intercom However wlreless lntercom IS a system there ~() Ineo n e C(Ul

communicate w1th each other 111 the same small a r ea (h ousr n bllil cll llg)

without using wire d links but for powered intcrcnm SOIneon e ju s t need to

plu g it to th e power supply without worryll1g on h ow to lin k the Inl r](om

By u s ing thi s techno logy it is more con venien t for the c u stomer tu put the

in tercom system s w ith ou t worrym g how to Ill s t ltl ll (mess) w lr(d) and n1lll(

o rganized Neve rtheless a lot o f problems to imple m ent this 1lt11lc o f

sys te m s

For th IS thesis the c haracteris tics on th~ powtrn ml errC)m ~11 1 hI

s tudied befo re Implement the product Neve rth eless thi S repo rt is Iso

s tudy case all the advan ced of telecommuI1Ication s

Chapter 2

Literature Review of Powered Intercom Project

21 WHAT IS COMMUNICATION

211 THE BLOCK DIAGRAM OF A COMMUNICATION SYSTEM

Fi gure 20 shows a cOllullonly used model Il) 1 Cl l l ll 1l l J11 iCl li u ll sy --lun

-l lhough it - lIggcsls a system -or cOllllllunicaLion be1ccn t u ICllhdCh InL~I(t d

or sonar In I hich Ihe system input and output 111 1 be localed 11 Ihe 11e ie

Regardless of the particular application and conli gu-iln II 11l1l1 lmli

trallsmission systems invariably involve three lllZljor sUbSYS tlll l ~~ 11l1bIl1lIloCl Ihl

channeL and d receiver In this literature review we II I lI s lul l bmiddot I h lllkill ~ t11 LLrI1l S

01 systems ror transk r of inforlllation between rcmolch IIK ll ed poi nls II is

limited to such systellls

mes sage message

sgnat

Inp~Jt

transducer T fansmlU8r

carner

Iransmll signal

R8C81ver

addl11ve nOise Interfereflce dls tNtlon res lJolllng from ba~d limlitl119 and non Ilns-cHllls S

c u lpu t ~IJnal

OIJIPll t jrr1sJu cer

Fig 2 I Block d iagram of a communic8 tion sys lcm (Rl fc 10 Re k l llU IIII

2111 Input Transducer

The vide vanety of possible sources of informatlOn refmiddota lll S III ffi JIlV (11 1 h 1r11 1

[arms [or mess a pes Regardless of their exa c t form hOW (lr IncSS rq~~e s 1Tl1 ~

be categorized as analog or digliol The former tTl) be 1ll 1l(lt-lt- cJ s fU Il CIIlt1I 1S

of a continu ous-time variable ([or example press u re t ll n pcrdl lll4 spLrch

mus iC l whereas the latter consist of discrete symbols (for rX d rnpk 1 nlt tl

text) Almost lIwanably the message produced by a sOll rce mbl be

converted bv a transducer to a for m SUItable for til c p ltrti cul r I pe f

cnrn mU111Calion system employed For CX2lillplc 111 elre t riri11

com tT1urlicarions speech waves are converted b cl nllCiUphullf Lo nll ~e

variatIons Sucl a converted 11leSsage is referred to as 111( Incssnrlf siqnu

In thi s book therefore a signal can be Interpreted as the tmiddotu idtin l1 01 a

qua n tIty often a vOlt2gC or current with ti me

2112 Transmitter

The purpose of the transmitter is to couple the mc~sI1~ Lo Llw ~ (Inll c l

Altho ugh it is not uncommon to find the input transd u ce l dll l c lv u lu plcc1

to the trans111ission medium as for example in some interLonl s stC1l1~ iL is

often nccessary to modulate a carrier wave With the s lgn 1 flillTI tile 1111111

transducer Modulation is the systematic vanation 0 1 some illlni) u ll o f Ill

carrier such as amplitude) phase or frequency in alc nrd d l1Ce 1111

function of th e n1essage slgnal There are several reasons f(gt r 11 ing (~rncr

and modulating it Important ones are (l l for ease of ra ci lduo n 1 10 red u ce

noise and interference (3) for channel assignment (4 ) for m Ultiplex ing or

transmlssion of several messages over a single chnnnc1 ln cl (5 I f J U VL rCO ITI l

equipment limitations Several of these reasons are scJf-explanHory Olhns

such as the second ill become more mcaningfui later

In additIOn to modulation other primary functions performed by the

transmi tter a r c fil tering amplillcation and coup ling th e moct u[ed s ipnaJ tu

the channel Ifor example through an antenna or o th e r 1 pprl1 pr JIC c ( ICT I

4

PIIlt1II Ihidmftl lJaklumul H~drlUil Unl c r Sl ll Nl 1aV S1lt1 S arn~n k UNIVEllt~nl MILnSr ~~ w

2 11 3 Channel

Tl w channel can have m any different for m s the most [amil iaL pc-h p is

rh e channel that exists between tlI e transmittin g an ten n a nl ) c OlTImLrLlnl

radio s tat ion and the receivIng antenna of a rad i() 111 thi 5 ch ~ nIH1 the

transmitted slgn al propagates through the 8 trn ospllfr e Dr fn e s Pju rr t il e

receli1ng antenna Hoovever it is not uncommon to Jlnd lhl~ trlnnlI1lcr

hard-wired to the receiver as in most local te lephone syste m s Th S -hlnnl

is vastly differen t from the radio example However ~ I ~ htnncls hC1H )lIe

th ing in common the signal undergoes d egradation fn ln lld I1 S ll11 tr f 1 I

receiver Although this degradatIOn may occur at ~m POlllt or 1I

communication system block diagram lt is customan iy i1 S S~t( l ~ llC d t th lil t

channe1 alone This degrad a tion often results from nOl sc rll rl qhr r lin(lt-

on-ed signals or lIlterference but also may lIlclude o lh er (hSLO I UOll cllcLh 1S

Nell such as fad lng signallcvels multiple transIniss io n P ill-h s 8nd fillr nnf

More about these unwanted perturbatIOns will be pr esented llo lll v

2114 Receiver

The receivers fu n ction is to extract the desIred messag( lrofll Imiddothe ITr-I~ I f d

signal at the ch ill1nel output and to convert It to fUI In Sl lltlhle f lll lit

output transducer Although amplification rn3 be 11IIC or ti ll IIfb l Il

atlons per[onned by the receiver especially in radio ( ()TIl11l1nllal J1) I1 ~ ) wh(n

lhe recelved Si gn al m ay be extremely weak the rn __ ~ i ll Junc lio n uf dH r L l l I C i

is to demodula ie the received signal Oft en It IS d es ire d th lI rcCCIIl rl( output be a scaled possibly delayed version of th e mcssd gc s iYIrI I I h e

modli lator mput although in some cases a morc ge n creo l rnnclo ll I Ih e

input rnessage is desired However as a result of the p re s cll (c or nO ise d nd

distortion tlus operatIOn is less than ldeal Ways of ~pprn ] hillg Illl k11

5

case of perfec t recovery wi ll be discussed as we p roceed

211 5 Output Transducer

The outpu t transdu cer completes the communicatIOn svstem This knee

converts th e el~Ll ic s Ignal at its in pu t InLO t he f rm c1csll(d hv I he svsIt m

u ser Perh aps the m os t common OUlput tran sdu cer IS 1Iucl spIkcr

However the re ar e many oth er examples s u ch as tltlpe rccorckrs pers0I w]

computers meters and cath ode-r ay tubes an d etc

212 CHANNEL CHARACTERISTICS

Noise Sources

No ise in a co mmunica tion sys tem can be cl lsslficcl Jt1 to two 1-1 lt1

categori es depend ing on its source Noise generated bv compone nt w it hll1

a co mmunication system s u ch as resis tors eicclron lubes ii nel sol U-llI(

acti ve devices is referr ed to as internal nOise The second ca tc~nr p~l( rnal

noise r esults from sources out s ide a commul11cation system 1IIclLllthr

a tmospheri c man -m a de and extrate rrestrial sou rces

Atmospheri c noise results primarily fro m SP Uri O U S )dl n wmTS

gen erated by the n a tural e lec trical d ischarges wit llll the t111uraquoph ltl

a ssocia ted with thunderstorms It is commonly rcfc rrrd to rl S 1)11( or

spitcncs Below about 100 MHz th e fi e ld s trcl12th of such radw 1 o- S IS

in ve rsely propo rtio na l to frequen cy Almosph en c II IHSC IS Lh Ii ln IZf d 011

the time do m ai n by largeamplitude s ho rt-dura tion bu rs ls lild IS nne of t illt

p rime examples o f n oise refe rred to as trl)I)[il~I(~ RecltlIlgte of llq i The

6

dependence on frequency atmospheric nOIse 8ffcrs ( CllllnWrCIltl1 A) l

broadcast radio which occupies the frequency ra n flc fm m 550 kfl lO 110

IIHiz m ore lh an it affects television and FM rd riio wlliill 11eldle in

lreq uency bands above 50 Mhz

i1a n - l11ade noise sources include high-voltage po( rl1 n ( corona dlS shy

charge COilllllUla to r-generated nOISE In electrica l lnotors aliturT10hik d

aircran 19ni t ion nOlse and switching-gear 1l00se Ign H lon n01~e (Hid

sWltching noise like atmospheric nOIse are Imru ls ivc in c Wfa uel lmpuhc

noise is Ih e predominant type of nOIse In switched vrc ll ne c hl lllwls gt11111

as lc1cphone channels For applicatlOlls such as Olee I rdJLsnli~si o I

Imp ulse noise is only an irritation factor hovrever It can 1)( ) s~ t J(Hl~

source of error in appilC3tIons involvIng transmIssion of cl lgnal el ata

Yet another importClrlL source of man -- Tn a de noist is LHlio- fr_~ qucncy

transmitters other than the one of Interest NUJSC Ju c to 1t1lcr tc nng

transmItters is commonly referred to as radlO-freq ll l1 cy in I e reTlllC( WFII

RFI IS p anicularly troublesome In SItuations 111 ~hICh i1 I ClC IIIIL dn tcllll ll IS

su bj ect to a high -density tran smitter environrrlen L -1 S Jn rnohdc

connn unications in a large city

Extraterrestrial noise sources include oLir sun and r)t l H~r ho t

heaven lv bodIes such as stars Owing to its high t Clllpcr)tlllT (tlfill(j C) md

rebliey close proximity to the earth the sun is an Intense bUI [UIIUllattiV

localized source of radio energy that extends ovcr a broad rrr-jl1lnry

spectrum Sim ilarly the stars are sources of wlde- iJalld rClth ~ntT0middot

Although m uch more distant and hence less ink n s e Ih lI1 t i l S II Il

7

nevertheless thev are collectively an importan t source o r n Oi s e IJCT 1 1 ~( n[

their vast numbers Radio stars such as quasars ltl nci p u lsm tgt t ~lbo

In l fnSe sources u f radio energy Considered a Sig ll Zll 5r1L1n c h v n~c1ln

astrCllt Omers such stars are vieved as anolher nlnSl oour( c bv

com nlun lc atlOlls l n gIneers The frequency f clngc or ~ oln r lind ( i JSIIlI C r1l)t~ C

exlends [rom a [evil megahertz to a fevv g igltlh e r t7 - 110Ih( 1 SOU l CC 01

Interference In communication systems is m u ltiple l r d ll s m ic clt)ll pt th s

These can resull from reflection off b u il d in gs th e (]rlh rp ln IK S lJleI

ShIpS or [rom refraclion by stratifications In the lranS ITlI S lt lnn Il t dlllln If

the scattering mechanism results in numerous [(fleeted (umpH1cnls be

received multipatb signal is noiselike and is ter m ed (l i(i 5e If lil e ITlUIUI l h

slgnal componen t IS composed of only one or tVO s lTnng 11 l tT tmiddotd fnv s 11 i ~

termed specular Finally signal degradatlOl1 In a corntn LtJl1 CiJ t0l1 ~ middot ~Ll nl C 1l1

occur because of random changes in attenuallOn w ilh lll 1 h e lril llSTn is SH11l

medium Such signal perturbations (disturbances) are rde n-cd Ln CiS Ji ) )

altbou g h it should be noted that specular m u itlp 1[h abo rcs llits III l l1 rlil1 ~

due to th e constructive and destructive interferen ce uf the Fltlird IIllllLlpk

signals

Typical usesFrequency Name Microwave Band (GHz)Band

Lon rnnsc n [11gnllon snnn r3 -30k l-l z c ry low frequency

Nai gatlonai 81tb rl(ilu30-300kHz Low frequen cy

IMm l imt nl liJo cli~ t I J S~ ilL Cmiddot1 11lJ1g cliree tlJ )1l flllcling COltlsl (jlla rd (( 111 111 lPnlIHLnlal IM rltIi S c IILIl m Ic c lc

nircrnfL Cllnl il l it ll

300-3000 Medium frequ en cy

ships telcgrmiddotp il tr lepllnne anu facsimd e ~llJp- flt- C iJ ~ t

3 - 30~ll-Iz High frequen cy (I-IF

VHF t eleJ~ioJl ( lhlnnltl 5 11 radio land lrdllltpOrlllinn

30-300 Very high frequency

private GHl c raft (tll t raffic cont rol laxi C Ilgt policr navlga noTlftl ltli ds

UHF tc IILgt n l hJIllll is raclto ~() n d( 11 1 I iris

03-3 Gl-lz Ultrahigh frequency 05- 10

suncd lI1lt( r ld r sw l i ite comm 1a dio ltiml le rs

20-30 30-40 40-6 0

10-2 0

s aleii lC lIlI1 lll Jldi~ alillh lc r 1l1l Cn)~1 illk~

Superhigh freq uency 60-80 3-30GI-lL

80- 100 airborn e rlc1 ar ltlpp rnarh radar middottotile r rdciar com m on

10- 124 citrrier Inn d m ollc 30-311lt] Extremel y hig h timiddotcq Rlilroad sen icc rOldOlr Iltlding

800-40 000 Infrared (80- 400) 10Hz) ~m

40k-75k Vis ible light (40-80) ~ tn Optl c01I C() llll JlL1 n11 ti (n~

GHz S vs tCln 75000- 1O~ 1 Ultrav iolet ligh t (12-40 ~ I r

G lIz wt1lltlcnq thj

Table 22 Frequ e ncy Bands With TypIcal Uses ([dc I to Reference II))

9

In ternal nOIse resu lts from th e random motIO n o f charge ca rri- in

e lect roni c com ponen ts It can be of two general types Iderrcd to s thermal

n(js e ca u sed by the random motion of free dcc rons In crmri u or or

SClnlCO n u c tor ~xci ted by th erm al agitation and shot 110 ~dtl cd by th e

runcom arrl aJ or discre te charge carriers 111 sllrh c1e lc( as lhen rllnnLc

tubes and semicondu ctor junc tion dev ices

2 2 Baseband signal types

We a re cons idering th e s ignals only a fter they have bCI OIne ek tnmiddott 1

s Igna ls s ta rt off in non-e lectncal fo rm (eg VOIce t-m per Itun) htlt 11(

been co nve rted to vo ltage u s ing some form o f tra n sdllce Ie g mluphollr middot

thermoeoll p ie)

These e lec trical sign als form the origina l Il1for lllttioll Illch i~ 10 he middot Ilt

the baseband O nce obtai ned they III always flli Il1 ln nc 01 two i)n)d

c la sses

221 Analogue signals

In these Ihe electri cal s igna l s h ows a contmu ous vari lt1l1 Ol1 II I rtmr five r a

wide ra nge of m agni tu des Ofte n th s tim e vanatton s the e Ll h tt of

an original non-elec trical signaJ (eg au preSSlll ltI nc ( I t ~gf In

microphone) so that the two arc sa Id to be ana logou s IWllce he nme of

analogue s ignal

Digital signals

IhcOsc e lec tr ica l siglla ls consi~ ( o r d iscontinuuus pu bes (or di ~It1 elel CIIIla lll ill

duc bu ciJ ltJ ngi ng tbluptl y tiom one d igi t to the nex l I lte Ire ll SI Idl ) led

S i t~lla l s as in a ld c~ prinl e r The most common type is o f cU UJC hill~ll ( lIdinL Ih Il

Chapter 1

Introduction of Powered Intercom Project

Introduction

A vast n e twork telecommunicatIOn llllks spans tltc in duS Trilaquolt zcd

COU ntne of the world carrymg telephone te legraph tclcvi ion n e5

p h ologra phs a nd ra dio programs ThIS n e twork IS con stro n llv heing

exp a nded a nd n ew invention s are increasin g its capaCIty ltIt breathtnllt lI1g

ra te The re were m any proble ms we have en cou ntered in th e bq~i l I inf( bu t

s lowly soluti on s have been found We have learn ed to li se the IlI1 llts m o re

e ffi c ie ntly a nd th e cos ts have dropped dramatIc a lly Nowodays there ltIre

m a n y typ es of links that has been use d to com mUI1lCCllr an ti Ilslng the

power su pply to co mmunicate is a new method

Inter com technology has been found 111 ea rlv 1 9~) Os ami s lowl It s

b een expanded to be used in local area network nor WIde lea network

Powered inter com is a new technology where It is slmi l r to lIinkss

intercom However wlreless lntercom IS a system there ~() Ineo n e C(Ul

communicate w1th each other 111 the same small a r ea (h ousr n bllil cll llg)

without using wire d links but for powered intcrcnm SOIneon e ju s t need to

plu g it to th e power supply without worryll1g on h ow to lin k the Inl r](om

By u s ing thi s techno logy it is more con venien t for the c u stomer tu put the

in tercom system s w ith ou t worrym g how to Ill s t ltl ll (mess) w lr(d) and n1lll(

o rganized Neve rtheless a lot o f problems to imple m ent this 1lt11lc o f

sys te m s

For th IS thesis the c haracteris tics on th~ powtrn ml errC)m ~11 1 hI

s tudied befo re Implement the product Neve rth eless thi S repo rt is Iso

s tudy case all the advan ced of telecommuI1Ication s

Chapter 2

Literature Review of Powered Intercom Project

21 WHAT IS COMMUNICATION

211 THE BLOCK DIAGRAM OF A COMMUNICATION SYSTEM

Fi gure 20 shows a cOllullonly used model Il) 1 Cl l l ll 1l l J11 iCl li u ll sy --lun

-l lhough it - lIggcsls a system -or cOllllllunicaLion be1ccn t u ICllhdCh InL~I(t d

or sonar In I hich Ihe system input and output 111 1 be localed 11 Ihe 11e ie

Regardless of the particular application and conli gu-iln II 11l1l1 lmli

trallsmission systems invariably involve three lllZljor sUbSYS tlll l ~~ 11l1bIl1lIloCl Ihl

channeL and d receiver In this literature review we II I lI s lul l bmiddot I h lllkill ~ t11 LLrI1l S

01 systems ror transk r of inforlllation between rcmolch IIK ll ed poi nls II is

limited to such systellls

mes sage message

sgnat

Inp~Jt

transducer T fansmlU8r

carner

Iransmll signal

R8C81ver

addl11ve nOise Interfereflce dls tNtlon res lJolllng from ba~d limlitl119 and non Ilns-cHllls S

c u lpu t ~IJnal

OIJIPll t jrr1sJu cer

Fig 2 I Block d iagram of a communic8 tion sys lcm (Rl fc 10 Re k l llU IIII

2111 Input Transducer

The vide vanety of possible sources of informatlOn refmiddota lll S III ffi JIlV (11 1 h 1r11 1

[arms [or mess a pes Regardless of their exa c t form hOW (lr IncSS rq~~e s 1Tl1 ~

be categorized as analog or digliol The former tTl) be 1ll 1l(lt-lt- cJ s fU Il CIIlt1I 1S

of a continu ous-time variable ([or example press u re t ll n pcrdl lll4 spLrch

mus iC l whereas the latter consist of discrete symbols (for rX d rnpk 1 nlt tl

text) Almost lIwanably the message produced by a sOll rce mbl be

converted bv a transducer to a for m SUItable for til c p ltrti cul r I pe f

cnrn mU111Calion system employed For CX2lillplc 111 elre t riri11

com tT1urlicarions speech waves are converted b cl nllCiUphullf Lo nll ~e

variatIons Sucl a converted 11leSsage is referred to as 111( Incssnrlf siqnu

In thi s book therefore a signal can be Interpreted as the tmiddotu idtin l1 01 a

qua n tIty often a vOlt2gC or current with ti me

2112 Transmitter

The purpose of the transmitter is to couple the mc~sI1~ Lo Llw ~ (Inll c l

Altho ugh it is not uncommon to find the input transd u ce l dll l c lv u lu plcc1

to the trans111ission medium as for example in some interLonl s stC1l1~ iL is

often nccessary to modulate a carrier wave With the s lgn 1 flillTI tile 1111111

transducer Modulation is the systematic vanation 0 1 some illlni) u ll o f Ill

carrier such as amplitude) phase or frequency in alc nrd d l1Ce 1111

function of th e n1essage slgnal There are several reasons f(gt r 11 ing (~rncr

and modulating it Important ones are (l l for ease of ra ci lduo n 1 10 red u ce

noise and interference (3) for channel assignment (4 ) for m Ultiplex ing or

transmlssion of several messages over a single chnnnc1 ln cl (5 I f J U VL rCO ITI l

equipment limitations Several of these reasons are scJf-explanHory Olhns

such as the second ill become more mcaningfui later

In additIOn to modulation other primary functions performed by the

transmi tter a r c fil tering amplillcation and coup ling th e moct u[ed s ipnaJ tu

the channel Ifor example through an antenna or o th e r 1 pprl1 pr JIC c ( ICT I

4

PIIlt1II Ihidmftl lJaklumul H~drlUil Unl c r Sl ll Nl 1aV S1lt1 S arn~n k UNIVEllt~nl MILnSr ~~ w

2 11 3 Channel

Tl w channel can have m any different for m s the most [amil iaL pc-h p is

rh e channel that exists between tlI e transmittin g an ten n a nl ) c OlTImLrLlnl

radio s tat ion and the receivIng antenna of a rad i() 111 thi 5 ch ~ nIH1 the

transmitted slgn al propagates through the 8 trn ospllfr e Dr fn e s Pju rr t il e

receli1ng antenna Hoovever it is not uncommon to Jlnd lhl~ trlnnlI1lcr

hard-wired to the receiver as in most local te lephone syste m s Th S -hlnnl

is vastly differen t from the radio example However ~ I ~ htnncls hC1H )lIe

th ing in common the signal undergoes d egradation fn ln lld I1 S ll11 tr f 1 I

receiver Although this degradatIOn may occur at ~m POlllt or 1I

communication system block diagram lt is customan iy i1 S S~t( l ~ llC d t th lil t

channe1 alone This degrad a tion often results from nOl sc rll rl qhr r lin(lt-

on-ed signals or lIlterference but also may lIlclude o lh er (hSLO I UOll cllcLh 1S

Nell such as fad lng signallcvels multiple transIniss io n P ill-h s 8nd fillr nnf

More about these unwanted perturbatIOns will be pr esented llo lll v

2114 Receiver

The receivers fu n ction is to extract the desIred messag( lrofll Imiddothe ITr-I~ I f d

signal at the ch ill1nel output and to convert It to fUI In Sl lltlhle f lll lit

output transducer Although amplification rn3 be 11IIC or ti ll IIfb l Il

atlons per[onned by the receiver especially in radio ( ()TIl11l1nllal J1) I1 ~ ) wh(n

lhe recelved Si gn al m ay be extremely weak the rn __ ~ i ll Junc lio n uf dH r L l l I C i

is to demodula ie the received signal Oft en It IS d es ire d th lI rcCCIIl rl( output be a scaled possibly delayed version of th e mcssd gc s iYIrI I I h e

modli lator mput although in some cases a morc ge n creo l rnnclo ll I Ih e

input rnessage is desired However as a result of the p re s cll (c or nO ise d nd

distortion tlus operatIOn is less than ldeal Ways of ~pprn ] hillg Illl k11

5

case of perfec t recovery wi ll be discussed as we p roceed

211 5 Output Transducer

The outpu t transdu cer completes the communicatIOn svstem This knee

converts th e el~Ll ic s Ignal at its in pu t InLO t he f rm c1csll(d hv I he svsIt m

u ser Perh aps the m os t common OUlput tran sdu cer IS 1Iucl spIkcr

However the re ar e many oth er examples s u ch as tltlpe rccorckrs pers0I w]

computers meters and cath ode-r ay tubes an d etc

212 CHANNEL CHARACTERISTICS

Noise Sources

No ise in a co mmunica tion sys tem can be cl lsslficcl Jt1 to two 1-1 lt1

categori es depend ing on its source Noise generated bv compone nt w it hll1

a co mmunication system s u ch as resis tors eicclron lubes ii nel sol U-llI(

acti ve devices is referr ed to as internal nOise The second ca tc~nr p~l( rnal

noise r esults from sources out s ide a commul11cation system 1IIclLllthr

a tmospheri c man -m a de and extrate rrestrial sou rces

Atmospheri c noise results primarily fro m SP Uri O U S )dl n wmTS

gen erated by the n a tural e lec trical d ischarges wit llll the t111uraquoph ltl

a ssocia ted with thunderstorms It is commonly rcfc rrrd to rl S 1)11( or

spitcncs Below about 100 MHz th e fi e ld s trcl12th of such radw 1 o- S IS

in ve rsely propo rtio na l to frequen cy Almosph en c II IHSC IS Lh Ii ln IZf d 011

the time do m ai n by largeamplitude s ho rt-dura tion bu rs ls lild IS nne of t illt

p rime examples o f n oise refe rred to as trl)I)[il~I(~ RecltlIlgte of llq i The

6

dependence on frequency atmospheric nOIse 8ffcrs ( CllllnWrCIltl1 A) l

broadcast radio which occupies the frequency ra n flc fm m 550 kfl lO 110

IIHiz m ore lh an it affects television and FM rd riio wlliill 11eldle in

lreq uency bands above 50 Mhz

i1a n - l11ade noise sources include high-voltage po( rl1 n ( corona dlS shy

charge COilllllUla to r-generated nOISE In electrica l lnotors aliturT10hik d

aircran 19ni t ion nOlse and switching-gear 1l00se Ign H lon n01~e (Hid

sWltching noise like atmospheric nOIse are Imru ls ivc in c Wfa uel lmpuhc

noise is Ih e predominant type of nOIse In switched vrc ll ne c hl lllwls gt11111

as lc1cphone channels For applicatlOlls such as Olee I rdJLsnli~si o I

Imp ulse noise is only an irritation factor hovrever It can 1)( ) s~ t J(Hl~

source of error in appilC3tIons involvIng transmIssion of cl lgnal el ata

Yet another importClrlL source of man -- Tn a de noist is LHlio- fr_~ qucncy

transmitters other than the one of Interest NUJSC Ju c to 1t1lcr tc nng

transmItters is commonly referred to as radlO-freq ll l1 cy in I e reTlllC( WFII

RFI IS p anicularly troublesome In SItuations 111 ~hICh i1 I ClC IIIIL dn tcllll ll IS

su bj ect to a high -density tran smitter environrrlen L -1 S Jn rnohdc

connn unications in a large city

Extraterrestrial noise sources include oLir sun and r)t l H~r ho t

heaven lv bodIes such as stars Owing to its high t Clllpcr)tlllT (tlfill(j C) md

rebliey close proximity to the earth the sun is an Intense bUI [UIIUllattiV

localized source of radio energy that extends ovcr a broad rrr-jl1lnry

spectrum Sim ilarly the stars are sources of wlde- iJalld rClth ~ntT0middot

Although m uch more distant and hence less ink n s e Ih lI1 t i l S II Il

7

nevertheless thev are collectively an importan t source o r n Oi s e IJCT 1 1 ~( n[

their vast numbers Radio stars such as quasars ltl nci p u lsm tgt t ~lbo

In l fnSe sources u f radio energy Considered a Sig ll Zll 5r1L1n c h v n~c1ln

astrCllt Omers such stars are vieved as anolher nlnSl oour( c bv

com nlun lc atlOlls l n gIneers The frequency f clngc or ~ oln r lind ( i JSIIlI C r1l)t~ C

exlends [rom a [evil megahertz to a fevv g igltlh e r t7 - 110Ih( 1 SOU l CC 01

Interference In communication systems is m u ltiple l r d ll s m ic clt)ll pt th s

These can resull from reflection off b u il d in gs th e (]rlh rp ln IK S lJleI

ShIpS or [rom refraclion by stratifications In the lranS ITlI S lt lnn Il t dlllln If

the scattering mechanism results in numerous [(fleeted (umpH1cnls be

received multipatb signal is noiselike and is ter m ed (l i(i 5e If lil e ITlUIUI l h

slgnal componen t IS composed of only one or tVO s lTnng 11 l tT tmiddotd fnv s 11 i ~

termed specular Finally signal degradatlOl1 In a corntn LtJl1 CiJ t0l1 ~ middot ~Ll nl C 1l1

occur because of random changes in attenuallOn w ilh lll 1 h e lril llSTn is SH11l

medium Such signal perturbations (disturbances) are rde n-cd Ln CiS Ji ) )

altbou g h it should be noted that specular m u itlp 1[h abo rcs llits III l l1 rlil1 ~

due to th e constructive and destructive interferen ce uf the Fltlird IIllllLlpk

signals

Typical usesFrequency Name Microwave Band (GHz)Band

Lon rnnsc n [11gnllon snnn r3 -30k l-l z c ry low frequency

Nai gatlonai 81tb rl(ilu30-300kHz Low frequen cy

IMm l imt nl liJo cli~ t I J S~ ilL Cmiddot1 11lJ1g cliree tlJ )1l flllcling COltlsl (jlla rd (( 111 111 lPnlIHLnlal IM rltIi S c IILIl m Ic c lc

nircrnfL Cllnl il l it ll

300-3000 Medium frequ en cy

ships telcgrmiddotp il tr lepllnne anu facsimd e ~llJp- flt- C iJ ~ t

3 - 30~ll-Iz High frequen cy (I-IF

VHF t eleJ~ioJl ( lhlnnltl 5 11 radio land lrdllltpOrlllinn

30-300 Very high frequency

private GHl c raft (tll t raffic cont rol laxi C Ilgt policr navlga noTlftl ltli ds

UHF tc IILgt n l hJIllll is raclto ~() n d( 11 1 I iris

03-3 Gl-lz Ultrahigh frequency 05- 10

suncd lI1lt( r ld r sw l i ite comm 1a dio ltiml le rs

20-30 30-40 40-6 0

10-2 0

s aleii lC lIlI1 lll Jldi~ alillh lc r 1l1l Cn)~1 illk~

Superhigh freq uency 60-80 3-30GI-lL

80- 100 airborn e rlc1 ar ltlpp rnarh radar middottotile r rdciar com m on

10- 124 citrrier Inn d m ollc 30-311lt] Extremel y hig h timiddotcq Rlilroad sen icc rOldOlr Iltlding

800-40 000 Infrared (80- 400) 10Hz) ~m

40k-75k Vis ible light (40-80) ~ tn Optl c01I C() llll JlL1 n11 ti (n~

GHz S vs tCln 75000- 1O~ 1 Ultrav iolet ligh t (12-40 ~ I r

G lIz wt1lltlcnq thj

Table 22 Frequ e ncy Bands With TypIcal Uses ([dc I to Reference II))

9

In ternal nOIse resu lts from th e random motIO n o f charge ca rri- in

e lect roni c com ponen ts It can be of two general types Iderrcd to s thermal

n(js e ca u sed by the random motion of free dcc rons In crmri u or or

SClnlCO n u c tor ~xci ted by th erm al agitation and shot 110 ~dtl cd by th e

runcom arrl aJ or discre te charge carriers 111 sllrh c1e lc( as lhen rllnnLc

tubes and semicondu ctor junc tion dev ices

2 2 Baseband signal types

We a re cons idering th e s ignals only a fter they have bCI OIne ek tnmiddott 1

s Igna ls s ta rt off in non-e lectncal fo rm (eg VOIce t-m per Itun) htlt 11(

been co nve rted to vo ltage u s ing some form o f tra n sdllce Ie g mluphollr middot

thermoeoll p ie)

These e lec trical sign als form the origina l Il1for lllttioll Illch i~ 10 he middot Ilt

the baseband O nce obtai ned they III always flli Il1 ln nc 01 two i)n)d

c la sses

221 Analogue signals

In these Ihe electri cal s igna l s h ows a contmu ous vari lt1l1 Ol1 II I rtmr five r a

wide ra nge of m agni tu des Ofte n th s tim e vanatton s the e Ll h tt of

an original non-elec trical signaJ (eg au preSSlll ltI nc ( I t ~gf In

microphone) so that the two arc sa Id to be ana logou s IWllce he nme of

analogue s ignal

Digital signals

IhcOsc e lec tr ica l siglla ls consi~ ( o r d iscontinuuus pu bes (or di ~It1 elel CIIIla lll ill

duc bu ciJ ltJ ngi ng tbluptl y tiom one d igi t to the nex l I lte Ire ll SI Idl ) led

S i t~lla l s as in a ld c~ prinl e r The most common type is o f cU UJC hill~ll ( lIdinL Ih Il

Introduction

A vast n e twork telecommunicatIOn llllks spans tltc in duS Trilaquolt zcd

COU ntne of the world carrymg telephone te legraph tclcvi ion n e5

p h ologra phs a nd ra dio programs ThIS n e twork IS con stro n llv heing

exp a nded a nd n ew invention s are increasin g its capaCIty ltIt breathtnllt lI1g

ra te The re were m any proble ms we have en cou ntered in th e bq~i l I inf( bu t

s lowly soluti on s have been found We have learn ed to li se the IlI1 llts m o re

e ffi c ie ntly a nd th e cos ts have dropped dramatIc a lly Nowodays there ltIre

m a n y typ es of links that has been use d to com mUI1lCCllr an ti Ilslng the

power su pply to co mmunicate is a new method

Inter com technology has been found 111 ea rlv 1 9~) Os ami s lowl It s

b een expanded to be used in local area network nor WIde lea network

Powered inter com is a new technology where It is slmi l r to lIinkss

intercom However wlreless lntercom IS a system there ~() Ineo n e C(Ul

communicate w1th each other 111 the same small a r ea (h ousr n bllil cll llg)

without using wire d links but for powered intcrcnm SOIneon e ju s t need to

plu g it to th e power supply without worryll1g on h ow to lin k the Inl r](om

By u s ing thi s techno logy it is more con venien t for the c u stomer tu put the

in tercom system s w ith ou t worrym g how to Ill s t ltl ll (mess) w lr(d) and n1lll(

o rganized Neve rtheless a lot o f problems to imple m ent this 1lt11lc o f

sys te m s

For th IS thesis the c haracteris tics on th~ powtrn ml errC)m ~11 1 hI

s tudied befo re Implement the product Neve rth eless thi S repo rt is Iso

s tudy case all the advan ced of telecommuI1Ication s

Chapter 2

Literature Review of Powered Intercom Project

21 WHAT IS COMMUNICATION

211 THE BLOCK DIAGRAM OF A COMMUNICATION SYSTEM

Fi gure 20 shows a cOllullonly used model Il) 1 Cl l l ll 1l l J11 iCl li u ll sy --lun

-l lhough it - lIggcsls a system -or cOllllllunicaLion be1ccn t u ICllhdCh InL~I(t d

or sonar In I hich Ihe system input and output 111 1 be localed 11 Ihe 11e ie

Regardless of the particular application and conli gu-iln II 11l1l1 lmli

trallsmission systems invariably involve three lllZljor sUbSYS tlll l ~~ 11l1bIl1lIloCl Ihl

channeL and d receiver In this literature review we II I lI s lul l bmiddot I h lllkill ~ t11 LLrI1l S

01 systems ror transk r of inforlllation between rcmolch IIK ll ed poi nls II is

limited to such systellls

mes sage message

sgnat

Inp~Jt

transducer T fansmlU8r

carner

Iransmll signal

R8C81ver

addl11ve nOise Interfereflce dls tNtlon res lJolllng from ba~d limlitl119 and non Ilns-cHllls S

c u lpu t ~IJnal

OIJIPll t jrr1sJu cer

Fig 2 I Block d iagram of a communic8 tion sys lcm (Rl fc 10 Re k l llU IIII

2111 Input Transducer

The vide vanety of possible sources of informatlOn refmiddota lll S III ffi JIlV (11 1 h 1r11 1

[arms [or mess a pes Regardless of their exa c t form hOW (lr IncSS rq~~e s 1Tl1 ~

be categorized as analog or digliol The former tTl) be 1ll 1l(lt-lt- cJ s fU Il CIIlt1I 1S

of a continu ous-time variable ([or example press u re t ll n pcrdl lll4 spLrch

mus iC l whereas the latter consist of discrete symbols (for rX d rnpk 1 nlt tl

text) Almost lIwanably the message produced by a sOll rce mbl be

converted bv a transducer to a for m SUItable for til c p ltrti cul r I pe f

cnrn mU111Calion system employed For CX2lillplc 111 elre t riri11

com tT1urlicarions speech waves are converted b cl nllCiUphullf Lo nll ~e

variatIons Sucl a converted 11leSsage is referred to as 111( Incssnrlf siqnu

In thi s book therefore a signal can be Interpreted as the tmiddotu idtin l1 01 a

qua n tIty often a vOlt2gC or current with ti me

2112 Transmitter

The purpose of the transmitter is to couple the mc~sI1~ Lo Llw ~ (Inll c l

Altho ugh it is not uncommon to find the input transd u ce l dll l c lv u lu plcc1

to the trans111ission medium as for example in some interLonl s stC1l1~ iL is

often nccessary to modulate a carrier wave With the s lgn 1 flillTI tile 1111111

transducer Modulation is the systematic vanation 0 1 some illlni) u ll o f Ill

carrier such as amplitude) phase or frequency in alc nrd d l1Ce 1111

function of th e n1essage slgnal There are several reasons f(gt r 11 ing (~rncr

and modulating it Important ones are (l l for ease of ra ci lduo n 1 10 red u ce

noise and interference (3) for channel assignment (4 ) for m Ultiplex ing or

transmlssion of several messages over a single chnnnc1 ln cl (5 I f J U VL rCO ITI l

equipment limitations Several of these reasons are scJf-explanHory Olhns

such as the second ill become more mcaningfui later

In additIOn to modulation other primary functions performed by the

transmi tter a r c fil tering amplillcation and coup ling th e moct u[ed s ipnaJ tu

the channel Ifor example through an antenna or o th e r 1 pprl1 pr JIC c ( ICT I

4

PIIlt1II Ihidmftl lJaklumul H~drlUil Unl c r Sl ll Nl 1aV S1lt1 S arn~n k UNIVEllt~nl MILnSr ~~ w

2 11 3 Channel

Tl w channel can have m any different for m s the most [amil iaL pc-h p is

rh e channel that exists between tlI e transmittin g an ten n a nl ) c OlTImLrLlnl

radio s tat ion and the receivIng antenna of a rad i() 111 thi 5 ch ~ nIH1 the

transmitted slgn al propagates through the 8 trn ospllfr e Dr fn e s Pju rr t il e

receli1ng antenna Hoovever it is not uncommon to Jlnd lhl~ trlnnlI1lcr

hard-wired to the receiver as in most local te lephone syste m s Th S -hlnnl

is vastly differen t from the radio example However ~ I ~ htnncls hC1H )lIe

th ing in common the signal undergoes d egradation fn ln lld I1 S ll11 tr f 1 I

receiver Although this degradatIOn may occur at ~m POlllt or 1I

communication system block diagram lt is customan iy i1 S S~t( l ~ llC d t th lil t

channe1 alone This degrad a tion often results from nOl sc rll rl qhr r lin(lt-

on-ed signals or lIlterference but also may lIlclude o lh er (hSLO I UOll cllcLh 1S

Nell such as fad lng signallcvels multiple transIniss io n P ill-h s 8nd fillr nnf

More about these unwanted perturbatIOns will be pr esented llo lll v

2114 Receiver

The receivers fu n ction is to extract the desIred messag( lrofll Imiddothe ITr-I~ I f d

signal at the ch ill1nel output and to convert It to fUI In Sl lltlhle f lll lit

output transducer Although amplification rn3 be 11IIC or ti ll IIfb l Il

atlons per[onned by the receiver especially in radio ( ()TIl11l1nllal J1) I1 ~ ) wh(n

lhe recelved Si gn al m ay be extremely weak the rn __ ~ i ll Junc lio n uf dH r L l l I C i

is to demodula ie the received signal Oft en It IS d es ire d th lI rcCCIIl rl( output be a scaled possibly delayed version of th e mcssd gc s iYIrI I I h e

modli lator mput although in some cases a morc ge n creo l rnnclo ll I Ih e

input rnessage is desired However as a result of the p re s cll (c or nO ise d nd

distortion tlus operatIOn is less than ldeal Ways of ~pprn ] hillg Illl k11

5

case of perfec t recovery wi ll be discussed as we p roceed

211 5 Output Transducer

The outpu t transdu cer completes the communicatIOn svstem This knee

converts th e el~Ll ic s Ignal at its in pu t InLO t he f rm c1csll(d hv I he svsIt m

u ser Perh aps the m os t common OUlput tran sdu cer IS 1Iucl spIkcr

However the re ar e many oth er examples s u ch as tltlpe rccorckrs pers0I w]

computers meters and cath ode-r ay tubes an d etc

212 CHANNEL CHARACTERISTICS

Noise Sources

No ise in a co mmunica tion sys tem can be cl lsslficcl Jt1 to two 1-1 lt1

categori es depend ing on its source Noise generated bv compone nt w it hll1

a co mmunication system s u ch as resis tors eicclron lubes ii nel sol U-llI(

acti ve devices is referr ed to as internal nOise The second ca tc~nr p~l( rnal

noise r esults from sources out s ide a commul11cation system 1IIclLllthr

a tmospheri c man -m a de and extrate rrestrial sou rces

Atmospheri c noise results primarily fro m SP Uri O U S )dl n wmTS

gen erated by the n a tural e lec trical d ischarges wit llll the t111uraquoph ltl

a ssocia ted with thunderstorms It is commonly rcfc rrrd to rl S 1)11( or

spitcncs Below about 100 MHz th e fi e ld s trcl12th of such radw 1 o- S IS

in ve rsely propo rtio na l to frequen cy Almosph en c II IHSC IS Lh Ii ln IZf d 011

the time do m ai n by largeamplitude s ho rt-dura tion bu rs ls lild IS nne of t illt

p rime examples o f n oise refe rred to as trl)I)[il~I(~ RecltlIlgte of llq i The

6

dependence on frequency atmospheric nOIse 8ffcrs ( CllllnWrCIltl1 A) l

broadcast radio which occupies the frequency ra n flc fm m 550 kfl lO 110

IIHiz m ore lh an it affects television and FM rd riio wlliill 11eldle in

lreq uency bands above 50 Mhz

i1a n - l11ade noise sources include high-voltage po( rl1 n ( corona dlS shy

charge COilllllUla to r-generated nOISE In electrica l lnotors aliturT10hik d

aircran 19ni t ion nOlse and switching-gear 1l00se Ign H lon n01~e (Hid

sWltching noise like atmospheric nOIse are Imru ls ivc in c Wfa uel lmpuhc

noise is Ih e predominant type of nOIse In switched vrc ll ne c hl lllwls gt11111

as lc1cphone channels For applicatlOlls such as Olee I rdJLsnli~si o I

Imp ulse noise is only an irritation factor hovrever It can 1)( ) s~ t J(Hl~

source of error in appilC3tIons involvIng transmIssion of cl lgnal el ata

Yet another importClrlL source of man -- Tn a de noist is LHlio- fr_~ qucncy

transmitters other than the one of Interest NUJSC Ju c to 1t1lcr tc nng

transmItters is commonly referred to as radlO-freq ll l1 cy in I e reTlllC( WFII

RFI IS p anicularly troublesome In SItuations 111 ~hICh i1 I ClC IIIIL dn tcllll ll IS

su bj ect to a high -density tran smitter environrrlen L -1 S Jn rnohdc

connn unications in a large city

Extraterrestrial noise sources include oLir sun and r)t l H~r ho t

heaven lv bodIes such as stars Owing to its high t Clllpcr)tlllT (tlfill(j C) md

rebliey close proximity to the earth the sun is an Intense bUI [UIIUllattiV

localized source of radio energy that extends ovcr a broad rrr-jl1lnry

spectrum Sim ilarly the stars are sources of wlde- iJalld rClth ~ntT0middot

Although m uch more distant and hence less ink n s e Ih lI1 t i l S II Il

7

nevertheless thev are collectively an importan t source o r n Oi s e IJCT 1 1 ~( n[

their vast numbers Radio stars such as quasars ltl nci p u lsm tgt t ~lbo

In l fnSe sources u f radio energy Considered a Sig ll Zll 5r1L1n c h v n~c1ln

astrCllt Omers such stars are vieved as anolher nlnSl oour( c bv

com nlun lc atlOlls l n gIneers The frequency f clngc or ~ oln r lind ( i JSIIlI C r1l)t~ C

exlends [rom a [evil megahertz to a fevv g igltlh e r t7 - 110Ih( 1 SOU l CC 01

Interference In communication systems is m u ltiple l r d ll s m ic clt)ll pt th s

These can resull from reflection off b u il d in gs th e (]rlh rp ln IK S lJleI

ShIpS or [rom refraclion by stratifications In the lranS ITlI S lt lnn Il t dlllln If

the scattering mechanism results in numerous [(fleeted (umpH1cnls be

received multipatb signal is noiselike and is ter m ed (l i(i 5e If lil e ITlUIUI l h

slgnal componen t IS composed of only one or tVO s lTnng 11 l tT tmiddotd fnv s 11 i ~

termed specular Finally signal degradatlOl1 In a corntn LtJl1 CiJ t0l1 ~ middot ~Ll nl C 1l1

occur because of random changes in attenuallOn w ilh lll 1 h e lril llSTn is SH11l

medium Such signal perturbations (disturbances) are rde n-cd Ln CiS Ji ) )

altbou g h it should be noted that specular m u itlp 1[h abo rcs llits III l l1 rlil1 ~

due to th e constructive and destructive interferen ce uf the Fltlird IIllllLlpk

signals

Typical usesFrequency Name Microwave Band (GHz)Band

Lon rnnsc n [11gnllon snnn r3 -30k l-l z c ry low frequency

Nai gatlonai 81tb rl(ilu30-300kHz Low frequen cy

IMm l imt nl liJo cli~ t I J S~ ilL Cmiddot1 11lJ1g cliree tlJ )1l flllcling COltlsl (jlla rd (( 111 111 lPnlIHLnlal IM rltIi S c IILIl m Ic c lc

nircrnfL Cllnl il l it ll

300-3000 Medium frequ en cy

ships telcgrmiddotp il tr lepllnne anu facsimd e ~llJp- flt- C iJ ~ t

3 - 30~ll-Iz High frequen cy (I-IF

VHF t eleJ~ioJl ( lhlnnltl 5 11 radio land lrdllltpOrlllinn

30-300 Very high frequency

private GHl c raft (tll t raffic cont rol laxi C Ilgt policr navlga noTlftl ltli ds

UHF tc IILgt n l hJIllll is raclto ~() n d( 11 1 I iris

03-3 Gl-lz Ultrahigh frequency 05- 10

suncd lI1lt( r ld r sw l i ite comm 1a dio ltiml le rs

20-30 30-40 40-6 0

10-2 0

s aleii lC lIlI1 lll Jldi~ alillh lc r 1l1l Cn)~1 illk~

Superhigh freq uency 60-80 3-30GI-lL

80- 100 airborn e rlc1 ar ltlpp rnarh radar middottotile r rdciar com m on

10- 124 citrrier Inn d m ollc 30-311lt] Extremel y hig h timiddotcq Rlilroad sen icc rOldOlr Iltlding

800-40 000 Infrared (80- 400) 10Hz) ~m

40k-75k Vis ible light (40-80) ~ tn Optl c01I C() llll JlL1 n11 ti (n~

GHz S vs tCln 75000- 1O~ 1 Ultrav iolet ligh t (12-40 ~ I r

G lIz wt1lltlcnq thj

Table 22 Frequ e ncy Bands With TypIcal Uses ([dc I to Reference II))

9

In ternal nOIse resu lts from th e random motIO n o f charge ca rri- in

e lect roni c com ponen ts It can be of two general types Iderrcd to s thermal

n(js e ca u sed by the random motion of free dcc rons In crmri u or or

SClnlCO n u c tor ~xci ted by th erm al agitation and shot 110 ~dtl cd by th e

runcom arrl aJ or discre te charge carriers 111 sllrh c1e lc( as lhen rllnnLc

tubes and semicondu ctor junc tion dev ices

2 2 Baseband signal types

We a re cons idering th e s ignals only a fter they have bCI OIne ek tnmiddott 1

s Igna ls s ta rt off in non-e lectncal fo rm (eg VOIce t-m per Itun) htlt 11(

been co nve rted to vo ltage u s ing some form o f tra n sdllce Ie g mluphollr middot

thermoeoll p ie)

These e lec trical sign als form the origina l Il1for lllttioll Illch i~ 10 he middot Ilt

the baseband O nce obtai ned they III always flli Il1 ln nc 01 two i)n)d

c la sses

221 Analogue signals

In these Ihe electri cal s igna l s h ows a contmu ous vari lt1l1 Ol1 II I rtmr five r a

wide ra nge of m agni tu des Ofte n th s tim e vanatton s the e Ll h tt of

an original non-elec trical signaJ (eg au preSSlll ltI nc ( I t ~gf In

microphone) so that the two arc sa Id to be ana logou s IWllce he nme of

analogue s ignal

Digital signals

IhcOsc e lec tr ica l siglla ls consi~ ( o r d iscontinuuus pu bes (or di ~It1 elel CIIIla lll ill

duc bu ciJ ltJ ngi ng tbluptl y tiom one d igi t to the nex l I lte Ire ll SI Idl ) led

S i t~lla l s as in a ld c~ prinl e r The most common type is o f cU UJC hill~ll ( lIdinL Ih Il

Chapter 2

Literature Review of Powered Intercom Project

21 WHAT IS COMMUNICATION

211 THE BLOCK DIAGRAM OF A COMMUNICATION SYSTEM

Fi gure 20 shows a cOllullonly used model Il) 1 Cl l l ll 1l l J11 iCl li u ll sy --lun

-l lhough it - lIggcsls a system -or cOllllllunicaLion be1ccn t u ICllhdCh InL~I(t d

or sonar In I hich Ihe system input and output 111 1 be localed 11 Ihe 11e ie

Regardless of the particular application and conli gu-iln II 11l1l1 lmli

trallsmission systems invariably involve three lllZljor sUbSYS tlll l ~~ 11l1bIl1lIloCl Ihl

channeL and d receiver In this literature review we II I lI s lul l bmiddot I h lllkill ~ t11 LLrI1l S

01 systems ror transk r of inforlllation between rcmolch IIK ll ed poi nls II is

limited to such systellls

mes sage message

sgnat

Inp~Jt

transducer T fansmlU8r

carner

Iransmll signal

R8C81ver

addl11ve nOise Interfereflce dls tNtlon res lJolllng from ba~d limlitl119 and non Ilns-cHllls S

c u lpu t ~IJnal

OIJIPll t jrr1sJu cer

Fig 2 I Block d iagram of a communic8 tion sys lcm (Rl fc 10 Re k l llU IIII

2111 Input Transducer

The vide vanety of possible sources of informatlOn refmiddota lll S III ffi JIlV (11 1 h 1r11 1

[arms [or mess a pes Regardless of their exa c t form hOW (lr IncSS rq~~e s 1Tl1 ~

be categorized as analog or digliol The former tTl) be 1ll 1l(lt-lt- cJ s fU Il CIIlt1I 1S

of a continu ous-time variable ([or example press u re t ll n pcrdl lll4 spLrch

mus iC l whereas the latter consist of discrete symbols (for rX d rnpk 1 nlt tl

text) Almost lIwanably the message produced by a sOll rce mbl be

converted bv a transducer to a for m SUItable for til c p ltrti cul r I pe f

cnrn mU111Calion system employed For CX2lillplc 111 elre t riri11

com tT1urlicarions speech waves are converted b cl nllCiUphullf Lo nll ~e

variatIons Sucl a converted 11leSsage is referred to as 111( Incssnrlf siqnu

In thi s book therefore a signal can be Interpreted as the tmiddotu idtin l1 01 a

qua n tIty often a vOlt2gC or current with ti me

2112 Transmitter

The purpose of the transmitter is to couple the mc~sI1~ Lo Llw ~ (Inll c l

Altho ugh it is not uncommon to find the input transd u ce l dll l c lv u lu plcc1

to the trans111ission medium as for example in some interLonl s stC1l1~ iL is

often nccessary to modulate a carrier wave With the s lgn 1 flillTI tile 1111111

transducer Modulation is the systematic vanation 0 1 some illlni) u ll o f Ill

carrier such as amplitude) phase or frequency in alc nrd d l1Ce 1111

function of th e n1essage slgnal There are several reasons f(gt r 11 ing (~rncr

and modulating it Important ones are (l l for ease of ra ci lduo n 1 10 red u ce

noise and interference (3) for channel assignment (4 ) for m Ultiplex ing or

transmlssion of several messages over a single chnnnc1 ln cl (5 I f J U VL rCO ITI l

equipment limitations Several of these reasons are scJf-explanHory Olhns

such as the second ill become more mcaningfui later

In additIOn to modulation other primary functions performed by the

transmi tter a r c fil tering amplillcation and coup ling th e moct u[ed s ipnaJ tu

the channel Ifor example through an antenna or o th e r 1 pprl1 pr JIC c ( ICT I

4

PIIlt1II Ihidmftl lJaklumul H~drlUil Unl c r Sl ll Nl 1aV S1lt1 S arn~n k UNIVEllt~nl MILnSr ~~ w

2 11 3 Channel

Tl w channel can have m any different for m s the most [amil iaL pc-h p is

rh e channel that exists between tlI e transmittin g an ten n a nl ) c OlTImLrLlnl

radio s tat ion and the receivIng antenna of a rad i() 111 thi 5 ch ~ nIH1 the

transmitted slgn al propagates through the 8 trn ospllfr e Dr fn e s Pju rr t il e

receli1ng antenna Hoovever it is not uncommon to Jlnd lhl~ trlnnlI1lcr

hard-wired to the receiver as in most local te lephone syste m s Th S -hlnnl

is vastly differen t from the radio example However ~ I ~ htnncls hC1H )lIe

th ing in common the signal undergoes d egradation fn ln lld I1 S ll11 tr f 1 I

receiver Although this degradatIOn may occur at ~m POlllt or 1I

communication system block diagram lt is customan iy i1 S S~t( l ~ llC d t th lil t

channe1 alone This degrad a tion often results from nOl sc rll rl qhr r lin(lt-

on-ed signals or lIlterference but also may lIlclude o lh er (hSLO I UOll cllcLh 1S

Nell such as fad lng signallcvels multiple transIniss io n P ill-h s 8nd fillr nnf

More about these unwanted perturbatIOns will be pr esented llo lll v

2114 Receiver

The receivers fu n ction is to extract the desIred messag( lrofll Imiddothe ITr-I~ I f d

signal at the ch ill1nel output and to convert It to fUI In Sl lltlhle f lll lit

output transducer Although amplification rn3 be 11IIC or ti ll IIfb l Il

atlons per[onned by the receiver especially in radio ( ()TIl11l1nllal J1) I1 ~ ) wh(n

lhe recelved Si gn al m ay be extremely weak the rn __ ~ i ll Junc lio n uf dH r L l l I C i

is to demodula ie the received signal Oft en It IS d es ire d th lI rcCCIIl rl( output be a scaled possibly delayed version of th e mcssd gc s iYIrI I I h e

modli lator mput although in some cases a morc ge n creo l rnnclo ll I Ih e

input rnessage is desired However as a result of the p re s cll (c or nO ise d nd

distortion tlus operatIOn is less than ldeal Ways of ~pprn ] hillg Illl k11

5

case of perfec t recovery wi ll be discussed as we p roceed

211 5 Output Transducer

The outpu t transdu cer completes the communicatIOn svstem This knee

converts th e el~Ll ic s Ignal at its in pu t InLO t he f rm c1csll(d hv I he svsIt m

u ser Perh aps the m os t common OUlput tran sdu cer IS 1Iucl spIkcr

However the re ar e many oth er examples s u ch as tltlpe rccorckrs pers0I w]

computers meters and cath ode-r ay tubes an d etc

212 CHANNEL CHARACTERISTICS

Noise Sources

No ise in a co mmunica tion sys tem can be cl lsslficcl Jt1 to two 1-1 lt1

categori es depend ing on its source Noise generated bv compone nt w it hll1

a co mmunication system s u ch as resis tors eicclron lubes ii nel sol U-llI(

acti ve devices is referr ed to as internal nOise The second ca tc~nr p~l( rnal

noise r esults from sources out s ide a commul11cation system 1IIclLllthr

a tmospheri c man -m a de and extrate rrestrial sou rces

Atmospheri c noise results primarily fro m SP Uri O U S )dl n wmTS

gen erated by the n a tural e lec trical d ischarges wit llll the t111uraquoph ltl

a ssocia ted with thunderstorms It is commonly rcfc rrrd to rl S 1)11( or

spitcncs Below about 100 MHz th e fi e ld s trcl12th of such radw 1 o- S IS

in ve rsely propo rtio na l to frequen cy Almosph en c II IHSC IS Lh Ii ln IZf d 011

the time do m ai n by largeamplitude s ho rt-dura tion bu rs ls lild IS nne of t illt

p rime examples o f n oise refe rred to as trl)I)[il~I(~ RecltlIlgte of llq i The

6

dependence on frequency atmospheric nOIse 8ffcrs ( CllllnWrCIltl1 A) l

broadcast radio which occupies the frequency ra n flc fm m 550 kfl lO 110

IIHiz m ore lh an it affects television and FM rd riio wlliill 11eldle in

lreq uency bands above 50 Mhz

i1a n - l11ade noise sources include high-voltage po( rl1 n ( corona dlS shy

charge COilllllUla to r-generated nOISE In electrica l lnotors aliturT10hik d

aircran 19ni t ion nOlse and switching-gear 1l00se Ign H lon n01~e (Hid

sWltching noise like atmospheric nOIse are Imru ls ivc in c Wfa uel lmpuhc

noise is Ih e predominant type of nOIse In switched vrc ll ne c hl lllwls gt11111

as lc1cphone channels For applicatlOlls such as Olee I rdJLsnli~si o I

Imp ulse noise is only an irritation factor hovrever It can 1)( ) s~ t J(Hl~

source of error in appilC3tIons involvIng transmIssion of cl lgnal el ata

Yet another importClrlL source of man -- Tn a de noist is LHlio- fr_~ qucncy

transmitters other than the one of Interest NUJSC Ju c to 1t1lcr tc nng

transmItters is commonly referred to as radlO-freq ll l1 cy in I e reTlllC( WFII

RFI IS p anicularly troublesome In SItuations 111 ~hICh i1 I ClC IIIIL dn tcllll ll IS

su bj ect to a high -density tran smitter environrrlen L -1 S Jn rnohdc

connn unications in a large city

Extraterrestrial noise sources include oLir sun and r)t l H~r ho t

heaven lv bodIes such as stars Owing to its high t Clllpcr)tlllT (tlfill(j C) md

rebliey close proximity to the earth the sun is an Intense bUI [UIIUllattiV

localized source of radio energy that extends ovcr a broad rrr-jl1lnry

spectrum Sim ilarly the stars are sources of wlde- iJalld rClth ~ntT0middot

Although m uch more distant and hence less ink n s e Ih lI1 t i l S II Il

7

nevertheless thev are collectively an importan t source o r n Oi s e IJCT 1 1 ~( n[

their vast numbers Radio stars such as quasars ltl nci p u lsm tgt t ~lbo

In l fnSe sources u f radio energy Considered a Sig ll Zll 5r1L1n c h v n~c1ln

astrCllt Omers such stars are vieved as anolher nlnSl oour( c bv

com nlun lc atlOlls l n gIneers The frequency f clngc or ~ oln r lind ( i JSIIlI C r1l)t~ C

exlends [rom a [evil megahertz to a fevv g igltlh e r t7 - 110Ih( 1 SOU l CC 01

Interference In communication systems is m u ltiple l r d ll s m ic clt)ll pt th s

These can resull from reflection off b u il d in gs th e (]rlh rp ln IK S lJleI

ShIpS or [rom refraclion by stratifications In the lranS ITlI S lt lnn Il t dlllln If

the scattering mechanism results in numerous [(fleeted (umpH1cnls be

received multipatb signal is noiselike and is ter m ed (l i(i 5e If lil e ITlUIUI l h

slgnal componen t IS composed of only one or tVO s lTnng 11 l tT tmiddotd fnv s 11 i ~

termed specular Finally signal degradatlOl1 In a corntn LtJl1 CiJ t0l1 ~ middot ~Ll nl C 1l1

occur because of random changes in attenuallOn w ilh lll 1 h e lril llSTn is SH11l

medium Such signal perturbations (disturbances) are rde n-cd Ln CiS Ji ) )

altbou g h it should be noted that specular m u itlp 1[h abo rcs llits III l l1 rlil1 ~

due to th e constructive and destructive interferen ce uf the Fltlird IIllllLlpk

signals

Typical usesFrequency Name Microwave Band (GHz)Band

Lon rnnsc n [11gnllon snnn r3 -30k l-l z c ry low frequency

Nai gatlonai 81tb rl(ilu30-300kHz Low frequen cy

IMm l imt nl liJo cli~ t I J S~ ilL Cmiddot1 11lJ1g cliree tlJ )1l flllcling COltlsl (jlla rd (( 111 111 lPnlIHLnlal IM rltIi S c IILIl m Ic c lc

nircrnfL Cllnl il l it ll

300-3000 Medium frequ en cy

ships telcgrmiddotp il tr lepllnne anu facsimd e ~llJp- flt- C iJ ~ t

3 - 30~ll-Iz High frequen cy (I-IF

VHF t eleJ~ioJl ( lhlnnltl 5 11 radio land lrdllltpOrlllinn

30-300 Very high frequency

private GHl c raft (tll t raffic cont rol laxi C Ilgt policr navlga noTlftl ltli ds

UHF tc IILgt n l hJIllll is raclto ~() n d( 11 1 I iris

03-3 Gl-lz Ultrahigh frequency 05- 10

suncd lI1lt( r ld r sw l i ite comm 1a dio ltiml le rs

20-30 30-40 40-6 0

10-2 0

s aleii lC lIlI1 lll Jldi~ alillh lc r 1l1l Cn)~1 illk~

Superhigh freq uency 60-80 3-30GI-lL

80- 100 airborn e rlc1 ar ltlpp rnarh radar middottotile r rdciar com m on

10- 124 citrrier Inn d m ollc 30-311lt] Extremel y hig h timiddotcq Rlilroad sen icc rOldOlr Iltlding

800-40 000 Infrared (80- 400) 10Hz) ~m

40k-75k Vis ible light (40-80) ~ tn Optl c01I C() llll JlL1 n11 ti (n~

GHz S vs tCln 75000- 1O~ 1 Ultrav iolet ligh t (12-40 ~ I r

G lIz wt1lltlcnq thj

Table 22 Frequ e ncy Bands With TypIcal Uses ([dc I to Reference II))

9

In ternal nOIse resu lts from th e random motIO n o f charge ca rri- in

e lect roni c com ponen ts It can be of two general types Iderrcd to s thermal

n(js e ca u sed by the random motion of free dcc rons In crmri u or or

SClnlCO n u c tor ~xci ted by th erm al agitation and shot 110 ~dtl cd by th e

runcom arrl aJ or discre te charge carriers 111 sllrh c1e lc( as lhen rllnnLc

tubes and semicondu ctor junc tion dev ices

2 2 Baseband signal types

We a re cons idering th e s ignals only a fter they have bCI OIne ek tnmiddott 1

s Igna ls s ta rt off in non-e lectncal fo rm (eg VOIce t-m per Itun) htlt 11(

been co nve rted to vo ltage u s ing some form o f tra n sdllce Ie g mluphollr middot

thermoeoll p ie)

These e lec trical sign als form the origina l Il1for lllttioll Illch i~ 10 he middot Ilt

the baseband O nce obtai ned they III always flli Il1 ln nc 01 two i)n)d

c la sses

221 Analogue signals

In these Ihe electri cal s igna l s h ows a contmu ous vari lt1l1 Ol1 II I rtmr five r a

wide ra nge of m agni tu des Ofte n th s tim e vanatton s the e Ll h tt of

an original non-elec trical signaJ (eg au preSSlll ltI nc ( I t ~gf In

microphone) so that the two arc sa Id to be ana logou s IWllce he nme of

analogue s ignal

Digital signals

IhcOsc e lec tr ica l siglla ls consi~ ( o r d iscontinuuus pu bes (or di ~It1 elel CIIIla lll ill

duc bu ciJ ltJ ngi ng tbluptl y tiom one d igi t to the nex l I lte Ire ll SI Idl ) led

S i t~lla l s as in a ld c~ prinl e r The most common type is o f cU UJC hill~ll ( lIdinL Ih Il

21 WHAT IS COMMUNICATION

211 THE BLOCK DIAGRAM OF A COMMUNICATION SYSTEM

Fi gure 20 shows a cOllullonly used model Il) 1 Cl l l ll 1l l J11 iCl li u ll sy --lun

-l lhough it - lIggcsls a system -or cOllllllunicaLion be1ccn t u ICllhdCh InL~I(t d

or sonar In I hich Ihe system input and output 111 1 be localed 11 Ihe 11e ie

Regardless of the particular application and conli gu-iln II 11l1l1 lmli

trallsmission systems invariably involve three lllZljor sUbSYS tlll l ~~ 11l1bIl1lIloCl Ihl

channeL and d receiver In this literature review we II I lI s lul l bmiddot I h lllkill ~ t11 LLrI1l S

01 systems ror transk r of inforlllation between rcmolch IIK ll ed poi nls II is

limited to such systellls

mes sage message

sgnat

Inp~Jt

transducer T fansmlU8r

carner

Iransmll signal

R8C81ver

addl11ve nOise Interfereflce dls tNtlon res lJolllng from ba~d limlitl119 and non Ilns-cHllls S

c u lpu t ~IJnal

OIJIPll t jrr1sJu cer

Fig 2 I Block d iagram of a communic8 tion sys lcm (Rl fc 10 Re k l llU IIII

2111 Input Transducer

The vide vanety of possible sources of informatlOn refmiddota lll S III ffi JIlV (11 1 h 1r11 1

[arms [or mess a pes Regardless of their exa c t form hOW (lr IncSS rq~~e s 1Tl1 ~

be categorized as analog or digliol The former tTl) be 1ll 1l(lt-lt- cJ s fU Il CIIlt1I 1S

of a continu ous-time variable ([or example press u re t ll n pcrdl lll4 spLrch

mus iC l whereas the latter consist of discrete symbols (for rX d rnpk 1 nlt tl

text) Almost lIwanably the message produced by a sOll rce mbl be

converted bv a transducer to a for m SUItable for til c p ltrti cul r I pe f

cnrn mU111Calion system employed For CX2lillplc 111 elre t riri11

com tT1urlicarions speech waves are converted b cl nllCiUphullf Lo nll ~e

variatIons Sucl a converted 11leSsage is referred to as 111( Incssnrlf siqnu

In thi s book therefore a signal can be Interpreted as the tmiddotu idtin l1 01 a

qua n tIty often a vOlt2gC or current with ti me

2112 Transmitter

The purpose of the transmitter is to couple the mc~sI1~ Lo Llw ~ (Inll c l

Altho ugh it is not uncommon to find the input transd u ce l dll l c lv u lu plcc1

to the trans111ission medium as for example in some interLonl s stC1l1~ iL is

often nccessary to modulate a carrier wave With the s lgn 1 flillTI tile 1111111

transducer Modulation is the systematic vanation 0 1 some illlni) u ll o f Ill

carrier such as amplitude) phase or frequency in alc nrd d l1Ce 1111

function of th e n1essage slgnal There are several reasons f(gt r 11 ing (~rncr

and modulating it Important ones are (l l for ease of ra ci lduo n 1 10 red u ce

noise and interference (3) for channel assignment (4 ) for m Ultiplex ing or

transmlssion of several messages over a single chnnnc1 ln cl (5 I f J U VL rCO ITI l

equipment limitations Several of these reasons are scJf-explanHory Olhns

such as the second ill become more mcaningfui later

In additIOn to modulation other primary functions performed by the

transmi tter a r c fil tering amplillcation and coup ling th e moct u[ed s ipnaJ tu

the channel Ifor example through an antenna or o th e r 1 pprl1 pr JIC c ( ICT I

4

PIIlt1II Ihidmftl lJaklumul H~drlUil Unl c r Sl ll Nl 1aV S1lt1 S arn~n k UNIVEllt~nl MILnSr ~~ w

2 11 3 Channel

Tl w channel can have m any different for m s the most [amil iaL pc-h p is

rh e channel that exists between tlI e transmittin g an ten n a nl ) c OlTImLrLlnl

radio s tat ion and the receivIng antenna of a rad i() 111 thi 5 ch ~ nIH1 the

transmitted slgn al propagates through the 8 trn ospllfr e Dr fn e s Pju rr t il e

receli1ng antenna Hoovever it is not uncommon to Jlnd lhl~ trlnnlI1lcr

hard-wired to the receiver as in most local te lephone syste m s Th S -hlnnl

is vastly differen t from the radio example However ~ I ~ htnncls hC1H )lIe

th ing in common the signal undergoes d egradation fn ln lld I1 S ll11 tr f 1 I

receiver Although this degradatIOn may occur at ~m POlllt or 1I

communication system block diagram lt is customan iy i1 S S~t( l ~ llC d t th lil t

channe1 alone This degrad a tion often results from nOl sc rll rl qhr r lin(lt-

on-ed signals or lIlterference but also may lIlclude o lh er (hSLO I UOll cllcLh 1S

Nell such as fad lng signallcvels multiple transIniss io n P ill-h s 8nd fillr nnf

More about these unwanted perturbatIOns will be pr esented llo lll v

2114 Receiver

The receivers fu n ction is to extract the desIred messag( lrofll Imiddothe ITr-I~ I f d

signal at the ch ill1nel output and to convert It to fUI In Sl lltlhle f lll lit

output transducer Although amplification rn3 be 11IIC or ti ll IIfb l Il

atlons per[onned by the receiver especially in radio ( ()TIl11l1nllal J1) I1 ~ ) wh(n

lhe recelved Si gn al m ay be extremely weak the rn __ ~ i ll Junc lio n uf dH r L l l I C i

is to demodula ie the received signal Oft en It IS d es ire d th lI rcCCIIl rl( output be a scaled possibly delayed version of th e mcssd gc s iYIrI I I h e

modli lator mput although in some cases a morc ge n creo l rnnclo ll I Ih e

input rnessage is desired However as a result of the p re s cll (c or nO ise d nd

distortion tlus operatIOn is less than ldeal Ways of ~pprn ] hillg Illl k11

5

case of perfec t recovery wi ll be discussed as we p roceed

211 5 Output Transducer

The outpu t transdu cer completes the communicatIOn svstem This knee

converts th e el~Ll ic s Ignal at its in pu t InLO t he f rm c1csll(d hv I he svsIt m

u ser Perh aps the m os t common OUlput tran sdu cer IS 1Iucl spIkcr

However the re ar e many oth er examples s u ch as tltlpe rccorckrs pers0I w]

computers meters and cath ode-r ay tubes an d etc

212 CHANNEL CHARACTERISTICS

Noise Sources

No ise in a co mmunica tion sys tem can be cl lsslficcl Jt1 to two 1-1 lt1

categori es depend ing on its source Noise generated bv compone nt w it hll1

a co mmunication system s u ch as resis tors eicclron lubes ii nel sol U-llI(

acti ve devices is referr ed to as internal nOise The second ca tc~nr p~l( rnal

noise r esults from sources out s ide a commul11cation system 1IIclLllthr

a tmospheri c man -m a de and extrate rrestrial sou rces

Atmospheri c noise results primarily fro m SP Uri O U S )dl n wmTS

gen erated by the n a tural e lec trical d ischarges wit llll the t111uraquoph ltl

a ssocia ted with thunderstorms It is commonly rcfc rrrd to rl S 1)11( or

spitcncs Below about 100 MHz th e fi e ld s trcl12th of such radw 1 o- S IS

in ve rsely propo rtio na l to frequen cy Almosph en c II IHSC IS Lh Ii ln IZf d 011

the time do m ai n by largeamplitude s ho rt-dura tion bu rs ls lild IS nne of t illt

p rime examples o f n oise refe rred to as trl)I)[il~I(~ RecltlIlgte of llq i The

6

dependence on frequency atmospheric nOIse 8ffcrs ( CllllnWrCIltl1 A) l

broadcast radio which occupies the frequency ra n flc fm m 550 kfl lO 110

IIHiz m ore lh an it affects television and FM rd riio wlliill 11eldle in

lreq uency bands above 50 Mhz

i1a n - l11ade noise sources include high-voltage po( rl1 n ( corona dlS shy

charge COilllllUla to r-generated nOISE In electrica l lnotors aliturT10hik d

aircran 19ni t ion nOlse and switching-gear 1l00se Ign H lon n01~e (Hid

sWltching noise like atmospheric nOIse are Imru ls ivc in c Wfa uel lmpuhc

noise is Ih e predominant type of nOIse In switched vrc ll ne c hl lllwls gt11111

as lc1cphone channels For applicatlOlls such as Olee I rdJLsnli~si o I

Imp ulse noise is only an irritation factor hovrever It can 1)( ) s~ t J(Hl~

source of error in appilC3tIons involvIng transmIssion of cl lgnal el ata

Yet another importClrlL source of man -- Tn a de noist is LHlio- fr_~ qucncy

transmitters other than the one of Interest NUJSC Ju c to 1t1lcr tc nng

transmItters is commonly referred to as radlO-freq ll l1 cy in I e reTlllC( WFII

RFI IS p anicularly troublesome In SItuations 111 ~hICh i1 I ClC IIIIL dn tcllll ll IS

su bj ect to a high -density tran smitter environrrlen L -1 S Jn rnohdc

connn unications in a large city

Extraterrestrial noise sources include oLir sun and r)t l H~r ho t

heaven lv bodIes such as stars Owing to its high t Clllpcr)tlllT (tlfill(j C) md

rebliey close proximity to the earth the sun is an Intense bUI [UIIUllattiV

localized source of radio energy that extends ovcr a broad rrr-jl1lnry

spectrum Sim ilarly the stars are sources of wlde- iJalld rClth ~ntT0middot

Although m uch more distant and hence less ink n s e Ih lI1 t i l S II Il

7

nevertheless thev are collectively an importan t source o r n Oi s e IJCT 1 1 ~( n[

their vast numbers Radio stars such as quasars ltl nci p u lsm tgt t ~lbo

In l fnSe sources u f radio energy Considered a Sig ll Zll 5r1L1n c h v n~c1ln

astrCllt Omers such stars are vieved as anolher nlnSl oour( c bv

com nlun lc atlOlls l n gIneers The frequency f clngc or ~ oln r lind ( i JSIIlI C r1l)t~ C

exlends [rom a [evil megahertz to a fevv g igltlh e r t7 - 110Ih( 1 SOU l CC 01

Interference In communication systems is m u ltiple l r d ll s m ic clt)ll pt th s

These can resull from reflection off b u il d in gs th e (]rlh rp ln IK S lJleI

ShIpS or [rom refraclion by stratifications In the lranS ITlI S lt lnn Il t dlllln If

the scattering mechanism results in numerous [(fleeted (umpH1cnls be

received multipatb signal is noiselike and is ter m ed (l i(i 5e If lil e ITlUIUI l h

slgnal componen t IS composed of only one or tVO s lTnng 11 l tT tmiddotd fnv s 11 i ~

termed specular Finally signal degradatlOl1 In a corntn LtJl1 CiJ t0l1 ~ middot ~Ll nl C 1l1

occur because of random changes in attenuallOn w ilh lll 1 h e lril llSTn is SH11l

medium Such signal perturbations (disturbances) are rde n-cd Ln CiS Ji ) )

altbou g h it should be noted that specular m u itlp 1[h abo rcs llits III l l1 rlil1 ~

due to th e constructive and destructive interferen ce uf the Fltlird IIllllLlpk

signals

Typical usesFrequency Name Microwave Band (GHz)Band

Lon rnnsc n [11gnllon snnn r3 -30k l-l z c ry low frequency

Nai gatlonai 81tb rl(ilu30-300kHz Low frequen cy

IMm l imt nl liJo cli~ t I J S~ ilL Cmiddot1 11lJ1g cliree tlJ )1l flllcling COltlsl (jlla rd (( 111 111 lPnlIHLnlal IM rltIi S c IILIl m Ic c lc

nircrnfL Cllnl il l it ll

300-3000 Medium frequ en cy

ships telcgrmiddotp il tr lepllnne anu facsimd e ~llJp- flt- C iJ ~ t

3 - 30~ll-Iz High frequen cy (I-IF

VHF t eleJ~ioJl ( lhlnnltl 5 11 radio land lrdllltpOrlllinn

30-300 Very high frequency

private GHl c raft (tll t raffic cont rol laxi C Ilgt policr navlga noTlftl ltli ds

UHF tc IILgt n l hJIllll is raclto ~() n d( 11 1 I iris

03-3 Gl-lz Ultrahigh frequency 05- 10

suncd lI1lt( r ld r sw l i ite comm 1a dio ltiml le rs

20-30 30-40 40-6 0

10-2 0

s aleii lC lIlI1 lll Jldi~ alillh lc r 1l1l Cn)~1 illk~

Superhigh freq uency 60-80 3-30GI-lL

80- 100 airborn e rlc1 ar ltlpp rnarh radar middottotile r rdciar com m on

10- 124 citrrier Inn d m ollc 30-311lt] Extremel y hig h timiddotcq Rlilroad sen icc rOldOlr Iltlding

800-40 000 Infrared (80- 400) 10Hz) ~m

40k-75k Vis ible light (40-80) ~ tn Optl c01I C() llll JlL1 n11 ti (n~

GHz S vs tCln 75000- 1O~ 1 Ultrav iolet ligh t (12-40 ~ I r

G lIz wt1lltlcnq thj

Table 22 Frequ e ncy Bands With TypIcal Uses ([dc I to Reference II))

9

In ternal nOIse resu lts from th e random motIO n o f charge ca rri- in

e lect roni c com ponen ts It can be of two general types Iderrcd to s thermal

n(js e ca u sed by the random motion of free dcc rons In crmri u or or

SClnlCO n u c tor ~xci ted by th erm al agitation and shot 110 ~dtl cd by th e

runcom arrl aJ or discre te charge carriers 111 sllrh c1e lc( as lhen rllnnLc

tubes and semicondu ctor junc tion dev ices

2 2 Baseband signal types

We a re cons idering th e s ignals only a fter they have bCI OIne ek tnmiddott 1

s Igna ls s ta rt off in non-e lectncal fo rm (eg VOIce t-m per Itun) htlt 11(

been co nve rted to vo ltage u s ing some form o f tra n sdllce Ie g mluphollr middot

thermoeoll p ie)

These e lec trical sign als form the origina l Il1for lllttioll Illch i~ 10 he middot Ilt

the baseband O nce obtai ned they III always flli Il1 ln nc 01 two i)n)d

c la sses

221 Analogue signals

In these Ihe electri cal s igna l s h ows a contmu ous vari lt1l1 Ol1 II I rtmr five r a

wide ra nge of m agni tu des Ofte n th s tim e vanatton s the e Ll h tt of

an original non-elec trical signaJ (eg au preSSlll ltI nc ( I t ~gf In

microphone) so that the two arc sa Id to be ana logou s IWllce he nme of

analogue s ignal

Digital signals

IhcOsc e lec tr ica l siglla ls consi~ ( o r d iscontinuuus pu bes (or di ~It1 elel CIIIla lll ill

duc bu ciJ ltJ ngi ng tbluptl y tiom one d igi t to the nex l I lte Ire ll SI Idl ) led

S i t~lla l s as in a ld c~ prinl e r The most common type is o f cU UJC hill~ll ( lIdinL Ih Il

mus iC l whereas the latter consist of discrete symbols (for rX d rnpk 1 nlt tl

text) Almost lIwanably the message produced by a sOll rce mbl be

converted bv a transducer to a for m SUItable for til c p ltrti cul r I pe f

cnrn mU111Calion system employed For CX2lillplc 111 elre t riri11

com tT1urlicarions speech waves are converted b cl nllCiUphullf Lo nll ~e

variatIons Sucl a converted 11leSsage is referred to as 111( Incssnrlf siqnu

In thi s book therefore a signal can be Interpreted as the tmiddotu idtin l1 01 a

qua n tIty often a vOlt2gC or current with ti me

2112 Transmitter

The purpose of the transmitter is to couple the mc~sI1~ Lo Llw ~ (Inll c l

Altho ugh it is not uncommon to find the input transd u ce l dll l c lv u lu plcc1

to the trans111ission medium as for example in some interLonl s stC1l1~ iL is

often nccessary to modulate a carrier wave With the s lgn 1 flillTI tile 1111111

transducer Modulation is the systematic vanation 0 1 some illlni) u ll o f Ill

carrier such as amplitude) phase or frequency in alc nrd d l1Ce 1111

function of th e n1essage slgnal There are several reasons f(gt r 11 ing (~rncr

and modulating it Important ones are (l l for ease of ra ci lduo n 1 10 red u ce

noise and interference (3) for channel assignment (4 ) for m Ultiplex ing or

transmlssion of several messages over a single chnnnc1 ln cl (5 I f J U VL rCO ITI l

equipment limitations Several of these reasons are scJf-explanHory Olhns

such as the second ill become more mcaningfui later

In additIOn to modulation other primary functions performed by the

transmi tter a r c fil tering amplillcation and coup ling th e moct u[ed s ipnaJ tu

the channel Ifor example through an antenna or o th e r 1 pprl1 pr JIC c ( ICT I

4

PIIlt1II Ihidmftl lJaklumul H~drlUil Unl c r Sl ll Nl 1aV S1lt1 S arn~n k UNIVEllt~nl MILnSr ~~ w

2 11 3 Channel

Tl w channel can have m any different for m s the most [amil iaL pc-h p is

rh e channel that exists between tlI e transmittin g an ten n a nl ) c OlTImLrLlnl

radio s tat ion and the receivIng antenna of a rad i() 111 thi 5 ch ~ nIH1 the

transmitted slgn al propagates through the 8 trn ospllfr e Dr fn e s Pju rr t il e

receli1ng antenna Hoovever it is not uncommon to Jlnd lhl~ trlnnlI1lcr

hard-wired to the receiver as in most local te lephone syste m s Th S -hlnnl

is vastly differen t from the radio example However ~ I ~ htnncls hC1H )lIe

th ing in common the signal undergoes d egradation fn ln lld I1 S ll11 tr f 1 I

receiver Although this degradatIOn may occur at ~m POlllt or 1I

communication system block diagram lt is customan iy i1 S S~t( l ~ llC d t th lil t

channe1 alone This degrad a tion often results from nOl sc rll rl qhr r lin(lt-

on-ed signals or lIlterference but also may lIlclude o lh er (hSLO I UOll cllcLh 1S

Nell such as fad lng signallcvels multiple transIniss io n P ill-h s 8nd fillr nnf

More about these unwanted perturbatIOns will be pr esented llo lll v

2114 Receiver

The receivers fu n ction is to extract the desIred messag( lrofll Imiddothe ITr-I~ I f d

signal at the ch ill1nel output and to convert It to fUI In Sl lltlhle f lll lit

output transducer Although amplification rn3 be 11IIC or ti ll IIfb l Il

atlons per[onned by the receiver especially in radio ( ()TIl11l1nllal J1) I1 ~ ) wh(n

lhe recelved Si gn al m ay be extremely weak the rn __ ~ i ll Junc lio n uf dH r L l l I C i

is to demodula ie the received signal Oft en It IS d es ire d th lI rcCCIIl rl( output be a scaled possibly delayed version of th e mcssd gc s iYIrI I I h e

modli lator mput although in some cases a morc ge n creo l rnnclo ll I Ih e

input rnessage is desired However as a result of the p re s cll (c or nO ise d nd

distortion tlus operatIOn is less than ldeal Ways of ~pprn ] hillg Illl k11

5

case of perfec t recovery wi ll be discussed as we p roceed

211 5 Output Transducer

The outpu t transdu cer completes the communicatIOn svstem This knee

converts th e el~Ll ic s Ignal at its in pu t InLO t he f rm c1csll(d hv I he svsIt m

u ser Perh aps the m os t common OUlput tran sdu cer IS 1Iucl spIkcr

However the re ar e many oth er examples s u ch as tltlpe rccorckrs pers0I w]

computers meters and cath ode-r ay tubes an d etc

212 CHANNEL CHARACTERISTICS

Noise Sources

No ise in a co mmunica tion sys tem can be cl lsslficcl Jt1 to two 1-1 lt1

categori es depend ing on its source Noise generated bv compone nt w it hll1

a co mmunication system s u ch as resis tors eicclron lubes ii nel sol U-llI(

acti ve devices is referr ed to as internal nOise The second ca tc~nr p~l( rnal

noise r esults from sources out s ide a commul11cation system 1IIclLllthr

a tmospheri c man -m a de and extrate rrestrial sou rces

Atmospheri c noise results primarily fro m SP Uri O U S )dl n wmTS

gen erated by the n a tural e lec trical d ischarges wit llll the t111uraquoph ltl

a ssocia ted with thunderstorms It is commonly rcfc rrrd to rl S 1)11( or

spitcncs Below about 100 MHz th e fi e ld s trcl12th of such radw 1 o- S IS

in ve rsely propo rtio na l to frequen cy Almosph en c II IHSC IS Lh Ii ln IZf d 011

the time do m ai n by largeamplitude s ho rt-dura tion bu rs ls lild IS nne of t illt

p rime examples o f n oise refe rred to as trl)I)[il~I(~ RecltlIlgte of llq i The

6

dependence on frequency atmospheric nOIse 8ffcrs ( CllllnWrCIltl1 A) l

broadcast radio which occupies the frequency ra n flc fm m 550 kfl lO 110

IIHiz m ore lh an it affects television and FM rd riio wlliill 11eldle in

lreq uency bands above 50 Mhz

i1a n - l11ade noise sources include high-voltage po( rl1 n ( corona dlS shy

charge COilllllUla to r-generated nOISE In electrica l lnotors aliturT10hik d

aircran 19ni t ion nOlse and switching-gear 1l00se Ign H lon n01~e (Hid

sWltching noise like atmospheric nOIse are Imru ls ivc in c Wfa uel lmpuhc

noise is Ih e predominant type of nOIse In switched vrc ll ne c hl lllwls gt11111

as lc1cphone channels For applicatlOlls such as Olee I rdJLsnli~si o I

Imp ulse noise is only an irritation factor hovrever It can 1)( ) s~ t J(Hl~

source of error in appilC3tIons involvIng transmIssion of cl lgnal el ata

Yet another importClrlL source of man -- Tn a de noist is LHlio- fr_~ qucncy

transmitters other than the one of Interest NUJSC Ju c to 1t1lcr tc nng

transmItters is commonly referred to as radlO-freq ll l1 cy in I e reTlllC( WFII

RFI IS p anicularly troublesome In SItuations 111 ~hICh i1 I ClC IIIIL dn tcllll ll IS

su bj ect to a high -density tran smitter environrrlen L -1 S Jn rnohdc

connn unications in a large city

Extraterrestrial noise sources include oLir sun and r)t l H~r ho t

heaven lv bodIes such as stars Owing to its high t Clllpcr)tlllT (tlfill(j C) md

rebliey close proximity to the earth the sun is an Intense bUI [UIIUllattiV

localized source of radio energy that extends ovcr a broad rrr-jl1lnry

spectrum Sim ilarly the stars are sources of wlde- iJalld rClth ~ntT0middot

Although m uch more distant and hence less ink n s e Ih lI1 t i l S II Il

7

nevertheless thev are collectively an importan t source o r n Oi s e IJCT 1 1 ~( n[

their vast numbers Radio stars such as quasars ltl nci p u lsm tgt t ~lbo

In l fnSe sources u f radio energy Considered a Sig ll Zll 5r1L1n c h v n~c1ln

astrCllt Omers such stars are vieved as anolher nlnSl oour( c bv

com nlun lc atlOlls l n gIneers The frequency f clngc or ~ oln r lind ( i JSIIlI C r1l)t~ C

exlends [rom a [evil megahertz to a fevv g igltlh e r t7 - 110Ih( 1 SOU l CC 01

Interference In communication systems is m u ltiple l r d ll s m ic clt)ll pt th s

These can resull from reflection off b u il d in gs th e (]rlh rp ln IK S lJleI

ShIpS or [rom refraclion by stratifications In the lranS ITlI S lt lnn Il t dlllln If

the scattering mechanism results in numerous [(fleeted (umpH1cnls be

received multipatb signal is noiselike and is ter m ed (l i(i 5e If lil e ITlUIUI l h

slgnal componen t IS composed of only one or tVO s lTnng 11 l tT tmiddotd fnv s 11 i ~

termed specular Finally signal degradatlOl1 In a corntn LtJl1 CiJ t0l1 ~ middot ~Ll nl C 1l1

occur because of random changes in attenuallOn w ilh lll 1 h e lril llSTn is SH11l

medium Such signal perturbations (disturbances) are rde n-cd Ln CiS Ji ) )

altbou g h it should be noted that specular m u itlp 1[h abo rcs llits III l l1 rlil1 ~

due to th e constructive and destructive interferen ce uf the Fltlird IIllllLlpk

signals

Typical usesFrequency Name Microwave Band (GHz)Band

Lon rnnsc n [11gnllon snnn r3 -30k l-l z c ry low frequency

Nai gatlonai 81tb rl(ilu30-300kHz Low frequen cy

IMm l imt nl liJo cli~ t I J S~ ilL Cmiddot1 11lJ1g cliree tlJ )1l flllcling COltlsl (jlla rd (( 111 111 lPnlIHLnlal IM rltIi S c IILIl m Ic c lc

nircrnfL Cllnl il l it ll

300-3000 Medium frequ en cy

ships telcgrmiddotp il tr lepllnne anu facsimd e ~llJp- flt- C iJ ~ t

3 - 30~ll-Iz High frequen cy (I-IF

VHF t eleJ~ioJl ( lhlnnltl 5 11 radio land lrdllltpOrlllinn

30-300 Very high frequency

private GHl c raft (tll t raffic cont rol laxi C Ilgt policr navlga noTlftl ltli ds

UHF tc IILgt n l hJIllll is raclto ~() n d( 11 1 I iris

03-3 Gl-lz Ultrahigh frequency 05- 10

suncd lI1lt( r ld r sw l i ite comm 1a dio ltiml le rs

20-30 30-40 40-6 0

10-2 0

s aleii lC lIlI1 lll Jldi~ alillh lc r 1l1l Cn)~1 illk~

Superhigh freq uency 60-80 3-30GI-lL

80- 100 airborn e rlc1 ar ltlpp rnarh radar middottotile r rdciar com m on

10- 124 citrrier Inn d m ollc 30-311lt] Extremel y hig h timiddotcq Rlilroad sen icc rOldOlr Iltlding

800-40 000 Infrared (80- 400) 10Hz) ~m

40k-75k Vis ible light (40-80) ~ tn Optl c01I C() llll JlL1 n11 ti (n~

GHz S vs tCln 75000- 1O~ 1 Ultrav iolet ligh t (12-40 ~ I r

G lIz wt1lltlcnq thj

Table 22 Frequ e ncy Bands With TypIcal Uses ([dc I to Reference II))

9

In ternal nOIse resu lts from th e random motIO n o f charge ca rri- in

e lect roni c com ponen ts It can be of two general types Iderrcd to s thermal

n(js e ca u sed by the random motion of free dcc rons In crmri u or or

SClnlCO n u c tor ~xci ted by th erm al agitation and shot 110 ~dtl cd by th e

runcom arrl aJ or discre te charge carriers 111 sllrh c1e lc( as lhen rllnnLc

tubes and semicondu ctor junc tion dev ices

2 2 Baseband signal types

We a re cons idering th e s ignals only a fter they have bCI OIne ek tnmiddott 1

s Igna ls s ta rt off in non-e lectncal fo rm (eg VOIce t-m per Itun) htlt 11(

been co nve rted to vo ltage u s ing some form o f tra n sdllce Ie g mluphollr middot

thermoeoll p ie)

These e lec trical sign als form the origina l Il1for lllttioll Illch i~ 10 he middot Ilt

the baseband O nce obtai ned they III always flli Il1 ln nc 01 two i)n)d

c la sses

221 Analogue signals

In these Ihe electri cal s igna l s h ows a contmu ous vari lt1l1 Ol1 II I rtmr five r a

wide ra nge of m agni tu des Ofte n th s tim e vanatton s the e Ll h tt of

an original non-elec trical signaJ (eg au preSSlll ltI nc ( I t ~gf In

microphone) so that the two arc sa Id to be ana logou s IWllce he nme of

analogue s ignal

Digital signals

IhcOsc e lec tr ica l siglla ls consi~ ( o r d iscontinuuus pu bes (or di ~It1 elel CIIIla lll ill

duc bu ciJ ltJ ngi ng tbluptl y tiom one d igi t to the nex l I lte Ire ll SI Idl ) led

S i t~lla l s as in a ld c~ prinl e r The most common type is o f cU UJC hill~ll ( lIdinL Ih Il

PIIlt1II Ihidmftl lJaklumul H~drlUil Unl c r Sl ll Nl 1aV S1lt1 S arn~n k UNIVEllt~nl MILnSr ~~ w

2 11 3 Channel

Tl w channel can have m any different for m s the most [amil iaL pc-h p is

rh e channel that exists between tlI e transmittin g an ten n a nl ) c OlTImLrLlnl

radio s tat ion and the receivIng antenna of a rad i() 111 thi 5 ch ~ nIH1 the

transmitted slgn al propagates through the 8 trn ospllfr e Dr fn e s Pju rr t il e

receli1ng antenna Hoovever it is not uncommon to Jlnd lhl~ trlnnlI1lcr

hard-wired to the receiver as in most local te lephone syste m s Th S -hlnnl

is vastly differen t from the radio example However ~ I ~ htnncls hC1H )lIe

th ing in common the signal undergoes d egradation fn ln lld I1 S ll11 tr f 1 I

receiver Although this degradatIOn may occur at ~m POlllt or 1I

communication system block diagram lt is customan iy i1 S S~t( l ~ llC d t th lil t

channe1 alone This degrad a tion often results from nOl sc rll rl qhr r lin(lt-

on-ed signals or lIlterference but also may lIlclude o lh er (hSLO I UOll cllcLh 1S

Nell such as fad lng signallcvels multiple transIniss io n P ill-h s 8nd fillr nnf

More about these unwanted perturbatIOns will be pr esented llo lll v

2114 Receiver

The receivers fu n ction is to extract the desIred messag( lrofll Imiddothe ITr-I~ I f d

signal at the ch ill1nel output and to convert It to fUI In Sl lltlhle f lll lit

output transducer Although amplification rn3 be 11IIC or ti ll IIfb l Il

atlons per[onned by the receiver especially in radio ( ()TIl11l1nllal J1) I1 ~ ) wh(n

lhe recelved Si gn al m ay be extremely weak the rn __ ~ i ll Junc lio n uf dH r L l l I C i

is to demodula ie the received signal Oft en It IS d es ire d th lI rcCCIIl rl( output be a scaled possibly delayed version of th e mcssd gc s iYIrI I I h e

modli lator mput although in some cases a morc ge n creo l rnnclo ll I Ih e

input rnessage is desired However as a result of the p re s cll (c or nO ise d nd

distortion tlus operatIOn is less than ldeal Ways of ~pprn ] hillg Illl k11

5

case of perfec t recovery wi ll be discussed as we p roceed

211 5 Output Transducer

The outpu t transdu cer completes the communicatIOn svstem This knee

converts th e el~Ll ic s Ignal at its in pu t InLO t he f rm c1csll(d hv I he svsIt m

u ser Perh aps the m os t common OUlput tran sdu cer IS 1Iucl spIkcr

However the re ar e many oth er examples s u ch as tltlpe rccorckrs pers0I w]

computers meters and cath ode-r ay tubes an d etc

212 CHANNEL CHARACTERISTICS

Noise Sources

No ise in a co mmunica tion sys tem can be cl lsslficcl Jt1 to two 1-1 lt1

categori es depend ing on its source Noise generated bv compone nt w it hll1

a co mmunication system s u ch as resis tors eicclron lubes ii nel sol U-llI(

acti ve devices is referr ed to as internal nOise The second ca tc~nr p~l( rnal

noise r esults from sources out s ide a commul11cation system 1IIclLllthr

a tmospheri c man -m a de and extrate rrestrial sou rces

Atmospheri c noise results primarily fro m SP Uri O U S )dl n wmTS

gen erated by the n a tural e lec trical d ischarges wit llll the t111uraquoph ltl

a ssocia ted with thunderstorms It is commonly rcfc rrrd to rl S 1)11( or

spitcncs Below about 100 MHz th e fi e ld s trcl12th of such radw 1 o- S IS

in ve rsely propo rtio na l to frequen cy Almosph en c II IHSC IS Lh Ii ln IZf d 011

the time do m ai n by largeamplitude s ho rt-dura tion bu rs ls lild IS nne of t illt

p rime examples o f n oise refe rred to as trl)I)[il~I(~ RecltlIlgte of llq i The

6

dependence on frequency atmospheric nOIse 8ffcrs ( CllllnWrCIltl1 A) l

broadcast radio which occupies the frequency ra n flc fm m 550 kfl lO 110

IIHiz m ore lh an it affects television and FM rd riio wlliill 11eldle in

lreq uency bands above 50 Mhz

i1a n - l11ade noise sources include high-voltage po( rl1 n ( corona dlS shy

charge COilllllUla to r-generated nOISE In electrica l lnotors aliturT10hik d

aircran 19ni t ion nOlse and switching-gear 1l00se Ign H lon n01~e (Hid

sWltching noise like atmospheric nOIse are Imru ls ivc in c Wfa uel lmpuhc

noise is Ih e predominant type of nOIse In switched vrc ll ne c hl lllwls gt11111

as lc1cphone channels For applicatlOlls such as Olee I rdJLsnli~si o I

Imp ulse noise is only an irritation factor hovrever It can 1)( ) s~ t J(Hl~

source of error in appilC3tIons involvIng transmIssion of cl lgnal el ata

Yet another importClrlL source of man -- Tn a de noist is LHlio- fr_~ qucncy

transmitters other than the one of Interest NUJSC Ju c to 1t1lcr tc nng

transmItters is commonly referred to as radlO-freq ll l1 cy in I e reTlllC( WFII

RFI IS p anicularly troublesome In SItuations 111 ~hICh i1 I ClC IIIIL dn tcllll ll IS

su bj ect to a high -density tran smitter environrrlen L -1 S Jn rnohdc

connn unications in a large city

Extraterrestrial noise sources include oLir sun and r)t l H~r ho t

heaven lv bodIes such as stars Owing to its high t Clllpcr)tlllT (tlfill(j C) md

rebliey close proximity to the earth the sun is an Intense bUI [UIIUllattiV

localized source of radio energy that extends ovcr a broad rrr-jl1lnry

spectrum Sim ilarly the stars are sources of wlde- iJalld rClth ~ntT0middot

Although m uch more distant and hence less ink n s e Ih lI1 t i l S II Il

7

nevertheless thev are collectively an importan t source o r n Oi s e IJCT 1 1 ~( n[

their vast numbers Radio stars such as quasars ltl nci p u lsm tgt t ~lbo

In l fnSe sources u f radio energy Considered a Sig ll Zll 5r1L1n c h v n~c1ln

astrCllt Omers such stars are vieved as anolher nlnSl oour( c bv

com nlun lc atlOlls l n gIneers The frequency f clngc or ~ oln r lind ( i JSIIlI C r1l)t~ C

exlends [rom a [evil megahertz to a fevv g igltlh e r t7 - 110Ih( 1 SOU l CC 01

Interference In communication systems is m u ltiple l r d ll s m ic clt)ll pt th s

These can resull from reflection off b u il d in gs th e (]rlh rp ln IK S lJleI

ShIpS or [rom refraclion by stratifications In the lranS ITlI S lt lnn Il t dlllln If

the scattering mechanism results in numerous [(fleeted (umpH1cnls be

received multipatb signal is noiselike and is ter m ed (l i(i 5e If lil e ITlUIUI l h

slgnal componen t IS composed of only one or tVO s lTnng 11 l tT tmiddotd fnv s 11 i ~

termed specular Finally signal degradatlOl1 In a corntn LtJl1 CiJ t0l1 ~ middot ~Ll nl C 1l1

occur because of random changes in attenuallOn w ilh lll 1 h e lril llSTn is SH11l

medium Such signal perturbations (disturbances) are rde n-cd Ln CiS Ji ) )

altbou g h it should be noted that specular m u itlp 1[h abo rcs llits III l l1 rlil1 ~

due to th e constructive and destructive interferen ce uf the Fltlird IIllllLlpk

signals

Typical usesFrequency Name Microwave Band (GHz)Band

Lon rnnsc n [11gnllon snnn r3 -30k l-l z c ry low frequency

Nai gatlonai 81tb rl(ilu30-300kHz Low frequen cy

IMm l imt nl liJo cli~ t I J S~ ilL Cmiddot1 11lJ1g cliree tlJ )1l flllcling COltlsl (jlla rd (( 111 111 lPnlIHLnlal IM rltIi S c IILIl m Ic c lc

nircrnfL Cllnl il l it ll

300-3000 Medium frequ en cy

ships telcgrmiddotp il tr lepllnne anu facsimd e ~llJp- flt- C iJ ~ t

3 - 30~ll-Iz High frequen cy (I-IF

VHF t eleJ~ioJl ( lhlnnltl 5 11 radio land lrdllltpOrlllinn

30-300 Very high frequency

private GHl c raft (tll t raffic cont rol laxi C Ilgt policr navlga noTlftl ltli ds

UHF tc IILgt n l hJIllll is raclto ~() n d( 11 1 I iris

03-3 Gl-lz Ultrahigh frequency 05- 10

suncd lI1lt( r ld r sw l i ite comm 1a dio ltiml le rs

20-30 30-40 40-6 0

10-2 0

s aleii lC lIlI1 lll Jldi~ alillh lc r 1l1l Cn)~1 illk~

Superhigh freq uency 60-80 3-30GI-lL

80- 100 airborn e rlc1 ar ltlpp rnarh radar middottotile r rdciar com m on

10- 124 citrrier Inn d m ollc 30-311lt] Extremel y hig h timiddotcq Rlilroad sen icc rOldOlr Iltlding

800-40 000 Infrared (80- 400) 10Hz) ~m

40k-75k Vis ible light (40-80) ~ tn Optl c01I C() llll JlL1 n11 ti (n~

GHz S vs tCln 75000- 1O~ 1 Ultrav iolet ligh t (12-40 ~ I r

G lIz wt1lltlcnq thj

Table 22 Frequ e ncy Bands With TypIcal Uses ([dc I to Reference II))

9

In ternal nOIse resu lts from th e random motIO n o f charge ca rri- in

e lect roni c com ponen ts It can be of two general types Iderrcd to s thermal

n(js e ca u sed by the random motion of free dcc rons In crmri u or or

SClnlCO n u c tor ~xci ted by th erm al agitation and shot 110 ~dtl cd by th e

runcom arrl aJ or discre te charge carriers 111 sllrh c1e lc( as lhen rllnnLc

tubes and semicondu ctor junc tion dev ices

2 2 Baseband signal types

We a re cons idering th e s ignals only a fter they have bCI OIne ek tnmiddott 1

s Igna ls s ta rt off in non-e lectncal fo rm (eg VOIce t-m per Itun) htlt 11(

been co nve rted to vo ltage u s ing some form o f tra n sdllce Ie g mluphollr middot

thermoeoll p ie)

These e lec trical sign als form the origina l Il1for lllttioll Illch i~ 10 he middot Ilt

the baseband O nce obtai ned they III always flli Il1 ln nc 01 two i)n)d

c la sses

221 Analogue signals

In these Ihe electri cal s igna l s h ows a contmu ous vari lt1l1 Ol1 II I rtmr five r a

wide ra nge of m agni tu des Ofte n th s tim e vanatton s the e Ll h tt of

an original non-elec trical signaJ (eg au preSSlll ltI nc ( I t ~gf In

microphone) so that the two arc sa Id to be ana logou s IWllce he nme of

analogue s ignal

Digital signals

IhcOsc e lec tr ica l siglla ls consi~ ( o r d iscontinuuus pu bes (or di ~It1 elel CIIIla lll ill

duc bu ciJ ltJ ngi ng tbluptl y tiom one d igi t to the nex l I lte Ire ll SI Idl ) led

S i t~lla l s as in a ld c~ prinl e r The most common type is o f cU UJC hill~ll ( lIdinL Ih Il

case of perfec t recovery wi ll be discussed as we p roceed

211 5 Output Transducer

The outpu t transdu cer completes the communicatIOn svstem This knee

converts th e el~Ll ic s Ignal at its in pu t InLO t he f rm c1csll(d hv I he svsIt m

u ser Perh aps the m os t common OUlput tran sdu cer IS 1Iucl spIkcr

However the re ar e many oth er examples s u ch as tltlpe rccorckrs pers0I w]

computers meters and cath ode-r ay tubes an d etc

212 CHANNEL CHARACTERISTICS

Noise Sources

No ise in a co mmunica tion sys tem can be cl lsslficcl Jt1 to two 1-1 lt1

categori es depend ing on its source Noise generated bv compone nt w it hll1

a co mmunication system s u ch as resis tors eicclron lubes ii nel sol U-llI(

acti ve devices is referr ed to as internal nOise The second ca tc~nr p~l( rnal

noise r esults from sources out s ide a commul11cation system 1IIclLllthr

a tmospheri c man -m a de and extrate rrestrial sou rces

Atmospheri c noise results primarily fro m SP Uri O U S )dl n wmTS

gen erated by the n a tural e lec trical d ischarges wit llll the t111uraquoph ltl

a ssocia ted with thunderstorms It is commonly rcfc rrrd to rl S 1)11( or

spitcncs Below about 100 MHz th e fi e ld s trcl12th of such radw 1 o- S IS

in ve rsely propo rtio na l to frequen cy Almosph en c II IHSC IS Lh Ii ln IZf d 011

the time do m ai n by largeamplitude s ho rt-dura tion bu rs ls lild IS nne of t illt

p rime examples o f n oise refe rred to as trl)I)[il~I(~ RecltlIlgte of llq i The

6

dependence on frequency atmospheric nOIse 8ffcrs ( CllllnWrCIltl1 A) l

broadcast radio which occupies the frequency ra n flc fm m 550 kfl lO 110

IIHiz m ore lh an it affects television and FM rd riio wlliill 11eldle in

lreq uency bands above 50 Mhz

i1a n - l11ade noise sources include high-voltage po( rl1 n ( corona dlS shy

charge COilllllUla to r-generated nOISE In electrica l lnotors aliturT10hik d

aircran 19ni t ion nOlse and switching-gear 1l00se Ign H lon n01~e (Hid

sWltching noise like atmospheric nOIse are Imru ls ivc in c Wfa uel lmpuhc

noise is Ih e predominant type of nOIse In switched vrc ll ne c hl lllwls gt11111

as lc1cphone channels For applicatlOlls such as Olee I rdJLsnli~si o I

Imp ulse noise is only an irritation factor hovrever It can 1)( ) s~ t J(Hl~

source of error in appilC3tIons involvIng transmIssion of cl lgnal el ata

Yet another importClrlL source of man -- Tn a de noist is LHlio- fr_~ qucncy

transmitters other than the one of Interest NUJSC Ju c to 1t1lcr tc nng

transmItters is commonly referred to as radlO-freq ll l1 cy in I e reTlllC( WFII

RFI IS p anicularly troublesome In SItuations 111 ~hICh i1 I ClC IIIIL dn tcllll ll IS

su bj ect to a high -density tran smitter environrrlen L -1 S Jn rnohdc

connn unications in a large city

Extraterrestrial noise sources include oLir sun and r)t l H~r ho t

heaven lv bodIes such as stars Owing to its high t Clllpcr)tlllT (tlfill(j C) md

rebliey close proximity to the earth the sun is an Intense bUI [UIIUllattiV

localized source of radio energy that extends ovcr a broad rrr-jl1lnry

spectrum Sim ilarly the stars are sources of wlde- iJalld rClth ~ntT0middot

Although m uch more distant and hence less ink n s e Ih lI1 t i l S II Il

7

nevertheless thev are collectively an importan t source o r n Oi s e IJCT 1 1 ~( n[

their vast numbers Radio stars such as quasars ltl nci p u lsm tgt t ~lbo

In l fnSe sources u f radio energy Considered a Sig ll Zll 5r1L1n c h v n~c1ln

astrCllt Omers such stars are vieved as anolher nlnSl oour( c bv

com nlun lc atlOlls l n gIneers The frequency f clngc or ~ oln r lind ( i JSIIlI C r1l)t~ C

exlends [rom a [evil megahertz to a fevv g igltlh e r t7 - 110Ih( 1 SOU l CC 01

Interference In communication systems is m u ltiple l r d ll s m ic clt)ll pt th s

These can resull from reflection off b u il d in gs th e (]rlh rp ln IK S lJleI

ShIpS or [rom refraclion by stratifications In the lranS ITlI S lt lnn Il t dlllln If

the scattering mechanism results in numerous [(fleeted (umpH1cnls be

received multipatb signal is noiselike and is ter m ed (l i(i 5e If lil e ITlUIUI l h

slgnal componen t IS composed of only one or tVO s lTnng 11 l tT tmiddotd fnv s 11 i ~

termed specular Finally signal degradatlOl1 In a corntn LtJl1 CiJ t0l1 ~ middot ~Ll nl C 1l1

occur because of random changes in attenuallOn w ilh lll 1 h e lril llSTn is SH11l

medium Such signal perturbations (disturbances) are rde n-cd Ln CiS Ji ) )

altbou g h it should be noted that specular m u itlp 1[h abo rcs llits III l l1 rlil1 ~

due to th e constructive and destructive interferen ce uf the Fltlird IIllllLlpk

signals

Typical usesFrequency Name Microwave Band (GHz)Band

Lon rnnsc n [11gnllon snnn r3 -30k l-l z c ry low frequency

Nai gatlonai 81tb rl(ilu30-300kHz Low frequen cy

IMm l imt nl liJo cli~ t I J S~ ilL Cmiddot1 11lJ1g cliree tlJ )1l flllcling COltlsl (jlla rd (( 111 111 lPnlIHLnlal IM rltIi S c IILIl m Ic c lc

nircrnfL Cllnl il l it ll

300-3000 Medium frequ en cy

ships telcgrmiddotp il tr lepllnne anu facsimd e ~llJp- flt- C iJ ~ t

3 - 30~ll-Iz High frequen cy (I-IF

VHF t eleJ~ioJl ( lhlnnltl 5 11 radio land lrdllltpOrlllinn

30-300 Very high frequency

private GHl c raft (tll t raffic cont rol laxi C Ilgt policr navlga noTlftl ltli ds

UHF tc IILgt n l hJIllll is raclto ~() n d( 11 1 I iris

03-3 Gl-lz Ultrahigh frequency 05- 10

suncd lI1lt( r ld r sw l i ite comm 1a dio ltiml le rs

20-30 30-40 40-6 0

10-2 0

s aleii lC lIlI1 lll Jldi~ alillh lc r 1l1l Cn)~1 illk~

Superhigh freq uency 60-80 3-30GI-lL

80- 100 airborn e rlc1 ar ltlpp rnarh radar middottotile r rdciar com m on

10- 124 citrrier Inn d m ollc 30-311lt] Extremel y hig h timiddotcq Rlilroad sen icc rOldOlr Iltlding

800-40 000 Infrared (80- 400) 10Hz) ~m

40k-75k Vis ible light (40-80) ~ tn Optl c01I C() llll JlL1 n11 ti (n~

GHz S vs tCln 75000- 1O~ 1 Ultrav iolet ligh t (12-40 ~ I r

G lIz wt1lltlcnq thj

Table 22 Frequ e ncy Bands With TypIcal Uses ([dc I to Reference II))

9

In ternal nOIse resu lts from th e random motIO n o f charge ca rri- in

e lect roni c com ponen ts It can be of two general types Iderrcd to s thermal

n(js e ca u sed by the random motion of free dcc rons In crmri u or or

SClnlCO n u c tor ~xci ted by th erm al agitation and shot 110 ~dtl cd by th e

runcom arrl aJ or discre te charge carriers 111 sllrh c1e lc( as lhen rllnnLc

tubes and semicondu ctor junc tion dev ices

2 2 Baseband signal types

We a re cons idering th e s ignals only a fter they have bCI OIne ek tnmiddott 1

s Igna ls s ta rt off in non-e lectncal fo rm (eg VOIce t-m per Itun) htlt 11(

been co nve rted to vo ltage u s ing some form o f tra n sdllce Ie g mluphollr middot

thermoeoll p ie)

These e lec trical sign als form the origina l Il1for lllttioll Illch i~ 10 he middot Ilt

the baseband O nce obtai ned they III always flli Il1 ln nc 01 two i)n)d

c la sses

221 Analogue signals

In these Ihe electri cal s igna l s h ows a contmu ous vari lt1l1 Ol1 II I rtmr five r a

wide ra nge of m agni tu des Ofte n th s tim e vanatton s the e Ll h tt of

an original non-elec trical signaJ (eg au preSSlll ltI nc ( I t ~gf In

microphone) so that the two arc sa Id to be ana logou s IWllce he nme of

analogue s ignal

Digital signals

IhcOsc e lec tr ica l siglla ls consi~ ( o r d iscontinuuus pu bes (or di ~It1 elel CIIIla lll ill

duc bu ciJ ltJ ngi ng tbluptl y tiom one d igi t to the nex l I lte Ire ll SI Idl ) led

S i t~lla l s as in a ld c~ prinl e r The most common type is o f cU UJC hill~ll ( lIdinL Ih Il

dependence on frequency atmospheric nOIse 8ffcrs ( CllllnWrCIltl1 A) l

broadcast radio which occupies the frequency ra n flc fm m 550 kfl lO 110

IIHiz m ore lh an it affects television and FM rd riio wlliill 11eldle in

lreq uency bands above 50 Mhz

i1a n - l11ade noise sources include high-voltage po( rl1 n ( corona dlS shy

charge COilllllUla to r-generated nOISE In electrica l lnotors aliturT10hik d

aircran 19ni t ion nOlse and switching-gear 1l00se Ign H lon n01~e (Hid

sWltching noise like atmospheric nOIse are Imru ls ivc in c Wfa uel lmpuhc

noise is Ih e predominant type of nOIse In switched vrc ll ne c hl lllwls gt11111

as lc1cphone channels For applicatlOlls such as Olee I rdJLsnli~si o I

Imp ulse noise is only an irritation factor hovrever It can 1)( ) s~ t J(Hl~

source of error in appilC3tIons involvIng transmIssion of cl lgnal el ata

Yet another importClrlL source of man -- Tn a de noist is LHlio- fr_~ qucncy

transmitters other than the one of Interest NUJSC Ju c to 1t1lcr tc nng

transmItters is commonly referred to as radlO-freq ll l1 cy in I e reTlllC( WFII

RFI IS p anicularly troublesome In SItuations 111 ~hICh i1 I ClC IIIIL dn tcllll ll IS

su bj ect to a high -density tran smitter environrrlen L -1 S Jn rnohdc

connn unications in a large city

Extraterrestrial noise sources include oLir sun and r)t l H~r ho t

heaven lv bodIes such as stars Owing to its high t Clllpcr)tlllT (tlfill(j C) md

rebliey close proximity to the earth the sun is an Intense bUI [UIIUllattiV

localized source of radio energy that extends ovcr a broad rrr-jl1lnry

spectrum Sim ilarly the stars are sources of wlde- iJalld rClth ~ntT0middot

Although m uch more distant and hence less ink n s e Ih lI1 t i l S II Il

7

nevertheless thev are collectively an importan t source o r n Oi s e IJCT 1 1 ~( n[

their vast numbers Radio stars such as quasars ltl nci p u lsm tgt t ~lbo

In l fnSe sources u f radio energy Considered a Sig ll Zll 5r1L1n c h v n~c1ln

astrCllt Omers such stars are vieved as anolher nlnSl oour( c bv

com nlun lc atlOlls l n gIneers The frequency f clngc or ~ oln r lind ( i JSIIlI C r1l)t~ C

exlends [rom a [evil megahertz to a fevv g igltlh e r t7 - 110Ih( 1 SOU l CC 01

Interference In communication systems is m u ltiple l r d ll s m ic clt)ll pt th s

These can resull from reflection off b u il d in gs th e (]rlh rp ln IK S lJleI

ShIpS or [rom refraclion by stratifications In the lranS ITlI S lt lnn Il t dlllln If

the scattering mechanism results in numerous [(fleeted (umpH1cnls be

received multipatb signal is noiselike and is ter m ed (l i(i 5e If lil e ITlUIUI l h

slgnal componen t IS composed of only one or tVO s lTnng 11 l tT tmiddotd fnv s 11 i ~

termed specular Finally signal degradatlOl1 In a corntn LtJl1 CiJ t0l1 ~ middot ~Ll nl C 1l1

occur because of random changes in attenuallOn w ilh lll 1 h e lril llSTn is SH11l

medium Such signal perturbations (disturbances) are rde n-cd Ln CiS Ji ) )

altbou g h it should be noted that specular m u itlp 1[h abo rcs llits III l l1 rlil1 ~

due to th e constructive and destructive interferen ce uf the Fltlird IIllllLlpk

signals

Typical usesFrequency Name Microwave Band (GHz)Band

Lon rnnsc n [11gnllon snnn r3 -30k l-l z c ry low frequency

Nai gatlonai 81tb rl(ilu30-300kHz Low frequen cy

IMm l imt nl liJo cli~ t I J S~ ilL Cmiddot1 11lJ1g cliree tlJ )1l flllcling COltlsl (jlla rd (( 111 111 lPnlIHLnlal IM rltIi S c IILIl m Ic c lc

nircrnfL Cllnl il l it ll

300-3000 Medium frequ en cy

ships telcgrmiddotp il tr lepllnne anu facsimd e ~llJp- flt- C iJ ~ t

3 - 30~ll-Iz High frequen cy (I-IF

VHF t eleJ~ioJl ( lhlnnltl 5 11 radio land lrdllltpOrlllinn

30-300 Very high frequency

private GHl c raft (tll t raffic cont rol laxi C Ilgt policr navlga noTlftl ltli ds

UHF tc IILgt n l hJIllll is raclto ~() n d( 11 1 I iris

03-3 Gl-lz Ultrahigh frequency 05- 10

suncd lI1lt( r ld r sw l i ite comm 1a dio ltiml le rs

20-30 30-40 40-6 0

10-2 0

s aleii lC lIlI1 lll Jldi~ alillh lc r 1l1l Cn)~1 illk~

Superhigh freq uency 60-80 3-30GI-lL

80- 100 airborn e rlc1 ar ltlpp rnarh radar middottotile r rdciar com m on

10- 124 citrrier Inn d m ollc 30-311lt] Extremel y hig h timiddotcq Rlilroad sen icc rOldOlr Iltlding

800-40 000 Infrared (80- 400) 10Hz) ~m

40k-75k Vis ible light (40-80) ~ tn Optl c01I C() llll JlL1 n11 ti (n~

GHz S vs tCln 75000- 1O~ 1 Ultrav iolet ligh t (12-40 ~ I r

G lIz wt1lltlcnq thj

Table 22 Frequ e ncy Bands With TypIcal Uses ([dc I to Reference II))

9

In ternal nOIse resu lts from th e random motIO n o f charge ca rri- in

e lect roni c com ponen ts It can be of two general types Iderrcd to s thermal

n(js e ca u sed by the random motion of free dcc rons In crmri u or or

SClnlCO n u c tor ~xci ted by th erm al agitation and shot 110 ~dtl cd by th e

runcom arrl aJ or discre te charge carriers 111 sllrh c1e lc( as lhen rllnnLc

tubes and semicondu ctor junc tion dev ices

2 2 Baseband signal types

We a re cons idering th e s ignals only a fter they have bCI OIne ek tnmiddott 1

s Igna ls s ta rt off in non-e lectncal fo rm (eg VOIce t-m per Itun) htlt 11(

been co nve rted to vo ltage u s ing some form o f tra n sdllce Ie g mluphollr middot

thermoeoll p ie)

These e lec trical sign als form the origina l Il1for lllttioll Illch i~ 10 he middot Ilt

the baseband O nce obtai ned they III always flli Il1 ln nc 01 two i)n)d

c la sses

221 Analogue signals

In these Ihe electri cal s igna l s h ows a contmu ous vari lt1l1 Ol1 II I rtmr five r a

wide ra nge of m agni tu des Ofte n th s tim e vanatton s the e Ll h tt of

an original non-elec trical signaJ (eg au preSSlll ltI nc ( I t ~gf In

microphone) so that the two arc sa Id to be ana logou s IWllce he nme of

analogue s ignal

Digital signals

IhcOsc e lec tr ica l siglla ls consi~ ( o r d iscontinuuus pu bes (or di ~It1 elel CIIIla lll ill

duc bu ciJ ltJ ngi ng tbluptl y tiom one d igi t to the nex l I lte Ire ll SI Idl ) led

S i t~lla l s as in a ld c~ prinl e r The most common type is o f cU UJC hill~ll ( lIdinL Ih Il

nevertheless thev are collectively an importan t source o r n Oi s e IJCT 1 1 ~( n[

their vast numbers Radio stars such as quasars ltl nci p u lsm tgt t ~lbo

In l fnSe sources u f radio energy Considered a Sig ll Zll 5r1L1n c h v n~c1ln

astrCllt Omers such stars are vieved as anolher nlnSl oour( c bv

com nlun lc atlOlls l n gIneers The frequency f clngc or ~ oln r lind ( i JSIIlI C r1l)t~ C

exlends [rom a [evil megahertz to a fevv g igltlh e r t7 - 110Ih( 1 SOU l CC 01

Interference In communication systems is m u ltiple l r d ll s m ic clt)ll pt th s

These can resull from reflection off b u il d in gs th e (]rlh rp ln IK S lJleI

ShIpS or [rom refraclion by stratifications In the lranS ITlI S lt lnn Il t dlllln If

the scattering mechanism results in numerous [(fleeted (umpH1cnls be

received multipatb signal is noiselike and is ter m ed (l i(i 5e If lil e ITlUIUI l h

slgnal componen t IS composed of only one or tVO s lTnng 11 l tT tmiddotd fnv s 11 i ~

termed specular Finally signal degradatlOl1 In a corntn LtJl1 CiJ t0l1 ~ middot ~Ll nl C 1l1

occur because of random changes in attenuallOn w ilh lll 1 h e lril llSTn is SH11l

medium Such signal perturbations (disturbances) are rde n-cd Ln CiS Ji ) )

altbou g h it should be noted that specular m u itlp 1[h abo rcs llits III l l1 rlil1 ~

due to th e constructive and destructive interferen ce uf the Fltlird IIllllLlpk

signals

Typical usesFrequency Name Microwave Band (GHz)Band

Lon rnnsc n [11gnllon snnn r3 -30k l-l z c ry low frequency

Nai gatlonai 81tb rl(ilu30-300kHz Low frequen cy

IMm l imt nl liJo cli~ t I J S~ ilL Cmiddot1 11lJ1g cliree tlJ )1l flllcling COltlsl (jlla rd (( 111 111 lPnlIHLnlal IM rltIi S c IILIl m Ic c lc

nircrnfL Cllnl il l it ll

300-3000 Medium frequ en cy

ships telcgrmiddotp il tr lepllnne anu facsimd e ~llJp- flt- C iJ ~ t

3 - 30~ll-Iz High frequen cy (I-IF

VHF t eleJ~ioJl ( lhlnnltl 5 11 radio land lrdllltpOrlllinn

30-300 Very high frequency

private GHl c raft (tll t raffic cont rol laxi C Ilgt policr navlga noTlftl ltli ds

UHF tc IILgt n l hJIllll is raclto ~() n d( 11 1 I iris

03-3 Gl-lz Ultrahigh frequency 05- 10

suncd lI1lt( r ld r sw l i ite comm 1a dio ltiml le rs

20-30 30-40 40-6 0

10-2 0

s aleii lC lIlI1 lll Jldi~ alillh lc r 1l1l Cn)~1 illk~

Superhigh freq uency 60-80 3-30GI-lL

80- 100 airborn e rlc1 ar ltlpp rnarh radar middottotile r rdciar com m on

10- 124 citrrier Inn d m ollc 30-311lt] Extremel y hig h timiddotcq Rlilroad sen icc rOldOlr Iltlding

800-40 000 Infrared (80- 400) 10Hz) ~m

40k-75k Vis ible light (40-80) ~ tn Optl c01I C() llll JlL1 n11 ti (n~

GHz S vs tCln 75000- 1O~ 1 Ultrav iolet ligh t (12-40 ~ I r

G lIz wt1lltlcnq thj

Table 22 Frequ e ncy Bands With TypIcal Uses ([dc I to Reference II))

9

In ternal nOIse resu lts from th e random motIO n o f charge ca rri- in

e lect roni c com ponen ts It can be of two general types Iderrcd to s thermal

n(js e ca u sed by the random motion of free dcc rons In crmri u or or

SClnlCO n u c tor ~xci ted by th erm al agitation and shot 110 ~dtl cd by th e

runcom arrl aJ or discre te charge carriers 111 sllrh c1e lc( as lhen rllnnLc

tubes and semicondu ctor junc tion dev ices

2 2 Baseband signal types

We a re cons idering th e s ignals only a fter they have bCI OIne ek tnmiddott 1

s Igna ls s ta rt off in non-e lectncal fo rm (eg VOIce t-m per Itun) htlt 11(

been co nve rted to vo ltage u s ing some form o f tra n sdllce Ie g mluphollr middot

thermoeoll p ie)

These e lec trical sign als form the origina l Il1for lllttioll Illch i~ 10 he middot Ilt

the baseband O nce obtai ned they III always flli Il1 ln nc 01 two i)n)d

c la sses

221 Analogue signals

In these Ihe electri cal s igna l s h ows a contmu ous vari lt1l1 Ol1 II I rtmr five r a

wide ra nge of m agni tu des Ofte n th s tim e vanatton s the e Ll h tt of

an original non-elec trical signaJ (eg au preSSlll ltI nc ( I t ~gf In

microphone) so that the two arc sa Id to be ana logou s IWllce he nme of

analogue s ignal

Digital signals

IhcOsc e lec tr ica l siglla ls consi~ ( o r d iscontinuuus pu bes (or di ~It1 elel CIIIla lll ill

duc bu ciJ ltJ ngi ng tbluptl y tiom one d igi t to the nex l I lte Ire ll SI Idl ) led

S i t~lla l s as in a ld c~ prinl e r The most common type is o f cU UJC hill~ll ( lIdinL Ih Il

Typical usesFrequency Name Microwave Band (GHz)Band

Lon rnnsc n [11gnllon snnn r3 -30k l-l z c ry low frequency

Nai gatlonai 81tb rl(ilu30-300kHz Low frequen cy

IMm l imt nl liJo cli~ t I J S~ ilL Cmiddot1 11lJ1g cliree tlJ )1l flllcling COltlsl (jlla rd (( 111 111 lPnlIHLnlal IM rltIi S c IILIl m Ic c lc

nircrnfL Cllnl il l it ll

300-3000 Medium frequ en cy

ships telcgrmiddotp il tr lepllnne anu facsimd e ~llJp- flt- C iJ ~ t

3 - 30~ll-Iz High frequen cy (I-IF

VHF t eleJ~ioJl ( lhlnnltl 5 11 radio land lrdllltpOrlllinn

30-300 Very high frequency

private GHl c raft (tll t raffic cont rol laxi C Ilgt policr navlga noTlftl ltli ds

UHF tc IILgt n l hJIllll is raclto ~() n d( 11 1 I iris

03-3 Gl-lz Ultrahigh frequency 05- 10

suncd lI1lt( r ld r sw l i ite comm 1a dio ltiml le rs

20-30 30-40 40-6 0

10-2 0

s aleii lC lIlI1 lll Jldi~ alillh lc r 1l1l Cn)~1 illk~

Superhigh freq uency 60-80 3-30GI-lL

80- 100 airborn e rlc1 ar ltlpp rnarh radar middottotile r rdciar com m on

10- 124 citrrier Inn d m ollc 30-311lt] Extremel y hig h timiddotcq Rlilroad sen icc rOldOlr Iltlding

800-40 000 Infrared (80- 400) 10Hz) ~m

40k-75k Vis ible light (40-80) ~ tn Optl c01I C() llll JlL1 n11 ti (n~

GHz S vs tCln 75000- 1O~ 1 Ultrav iolet ligh t (12-40 ~ I r

G lIz wt1lltlcnq thj

Table 22 Frequ e ncy Bands With TypIcal Uses ([dc I to Reference II))

9

In ternal nOIse resu lts from th e random motIO n o f charge ca rri- in

e lect roni c com ponen ts It can be of two general types Iderrcd to s thermal

n(js e ca u sed by the random motion of free dcc rons In crmri u or or

SClnlCO n u c tor ~xci ted by th erm al agitation and shot 110 ~dtl cd by th e

runcom arrl aJ or discre te charge carriers 111 sllrh c1e lc( as lhen rllnnLc

tubes and semicondu ctor junc tion dev ices

2 2 Baseband signal types

We a re cons idering th e s ignals only a fter they have bCI OIne ek tnmiddott 1

s Igna ls s ta rt off in non-e lectncal fo rm (eg VOIce t-m per Itun) htlt 11(

been co nve rted to vo ltage u s ing some form o f tra n sdllce Ie g mluphollr middot

thermoeoll p ie)

These e lec trical sign als form the origina l Il1for lllttioll Illch i~ 10 he middot Ilt

the baseband O nce obtai ned they III always flli Il1 ln nc 01 two i)n)d

c la sses

221 Analogue signals

In these Ihe electri cal s igna l s h ows a contmu ous vari lt1l1 Ol1 II I rtmr five r a

wide ra nge of m agni tu des Ofte n th s tim e vanatton s the e Ll h tt of

an original non-elec trical signaJ (eg au preSSlll ltI nc ( I t ~gf In

microphone) so that the two arc sa Id to be ana logou s IWllce he nme of

analogue s ignal

Digital signals

IhcOsc e lec tr ica l siglla ls consi~ ( o r d iscontinuuus pu bes (or di ~It1 elel CIIIla lll ill

duc bu ciJ ltJ ngi ng tbluptl y tiom one d igi t to the nex l I lte Ire ll SI Idl ) led

S i t~lla l s as in a ld c~ prinl e r The most common type is o f cU UJC hill~ll ( lIdinL Ih Il

In ternal nOIse resu lts from th e random motIO n o f charge ca rri- in

e lect roni c com ponen ts It can be of two general types Iderrcd to s thermal

n(js e ca u sed by the random motion of free dcc rons In crmri u or or

SClnlCO n u c tor ~xci ted by th erm al agitation and shot 110 ~dtl cd by th e

runcom arrl aJ or discre te charge carriers 111 sllrh c1e lc( as lhen rllnnLc

tubes and semicondu ctor junc tion dev ices

2 2 Baseband signal types

We a re cons idering th e s ignals only a fter they have bCI OIne ek tnmiddott 1

s Igna ls s ta rt off in non-e lectncal fo rm (eg VOIce t-m per Itun) htlt 11(

been co nve rted to vo ltage u s ing some form o f tra n sdllce Ie g mluphollr middot

thermoeoll p ie)

These e lec trical sign als form the origina l Il1for lllttioll Illch i~ 10 he middot Ilt

the baseband O nce obtai ned they III always flli Il1 ln nc 01 two i)n)d

c la sses

221 Analogue signals

In these Ihe electri cal s igna l s h ows a contmu ous vari lt1l1 Ol1 II I rtmr five r a

wide ra nge of m agni tu des Ofte n th s tim e vanatton s the e Ll h tt of

an original non-elec trical signaJ (eg au preSSlll ltI nc ( I t ~gf In

microphone) so that the two arc sa Id to be ana logou s IWllce he nme of

analogue s ignal

Digital signals

IhcOsc e lec tr ica l siglla ls consi~ ( o r d iscontinuuus pu bes (or di ~It1 elel CIIIla lll ill

duc bu ciJ ltJ ngi ng tbluptl y tiom one d igi t to the nex l I lte Ire ll SI Idl ) led

S i t~lla l s as in a ld c~ prinl e r The most common type is o f cU UJC hill~ll ( lIdinL Ih Il