Bai Tap Lon Mon Thu Phat
Transcript of Bai Tap Lon Mon Thu Phat
-
8/3/2019 Bai Tap Lon Mon Thu Phat
1/26
BI TP LN MN THIT B THU PHT V TUYN IN
MC LC
LI M U .......... 01
PHN : TNG QUAN V THIT B THU PHT .......... 02I.Tng quan v my pht v tuyn in. .......... 02
1. Khi nim: .......... 02
2. S khi .......... 03
3. Phn loi my pht: .......... 04
4. Cc ch tiu k thut ca my pht .......... 05
II. My thu .......... 07
1.Cc tham s k thut .......... 072.Phn loi my thu .......... 07
3. My thu khuch i thng: .......... 08
4. My thu i tn .08PHN II. PHN TCH S KHI,S TNG PHI HP TR KHNG
ANTEN CA MY THU PHT VT JSS-720 .......... 10
I. Phn tch phn pht .......... 10
1. Khi pht ca JSS 720 bao gm cc khi: .......... 102. Nhim v cc khi: .......... 10
3. Phn tch .......... 10
II. Phn tch phn thu .......... 14
1. Phn thu gm cc khi: .......... 14
2. Nhim v cc khi: .......... 14
3.Phn tch .......... 14
III. i su phn tch b phi hp tr khng anten JSS-720. .......... 171.Khi qut: .......... 17
2.S khi ca b iu hng: .......... 19
IV. KT LUN. .......... 26
trang:1
-
8/3/2019 Bai Tap Lon Mon Thu Phat
2/26
BI TP LN MN THIT B THU PHT V TUYN IN
LI M U
Ngy nay cng vi s pht trin mnh m ca thng tin v tuyn th thit b v
tuyn in(VT) ng mt vai tr rt quan trng trong vic truyn ti tin tc i xa.Thit b thu pht c s dng rt rng ri trong nhiu lnh vc thng tin nh vic pht
thanh truyn b cc thng tin i chng, cc thng tin qun s c bit thit b thu
pht c s dng trn cc tu thuyn nhm phc v cho mc ch an ton v cu nn
trn bin.
Thng tin lin lc trc khi c truyn i xa n phi c iu ch dch ln
min tn s cao c khi nng t bc x ra khng gian. Thit b thc hin x l tin tc,
iu ch v bc x sng in t gi l my pht v tuyn in. Thit b lm chc nngngc li gi l my thu v tuyn in.
M hnh truyn sng trong khng gian t do ca h thng thng tin VT :
nghin cu k hn sau y chng ta s nghin cu tng quan v thit b v
tuyn in v i su phn tch chi tit s khi ca my thu pht VT JSS-720.Phn
tch chi tit s phi hp tr khng.
trang:2
My pht vtuyn in
My thu v tuynin
Mi trng truyn
-
8/3/2019 Bai Tap Lon Mon Thu Phat
3/26
BI TP LN MN THIT B THU PHT V TUYN IN
PHN : TNG QUAN V THIT B THU PHT
I.Tng quan v my pht v tuyn in.
1. Khi nim:
My pht v tuyn in l mt thit b v tuyn in to ra dao ng cao tn a
vo anten bc x ra khng gian t do di dng sng in t truyn thng tin i
xa.
2. S khi
+> Khi dao ng: To ra mt tn s chun a vo khi iu ch
+> Ngun tin gm: Ngun tin tng t v ngun tin s. N to ra tin tc m pha thu
yu cu.
+> Khuch i tin tc: Khuch i bin tin tc ln a ti khi iu ch.
+> iu ch: Trn hai tn s t khi dao ng ti v t ngun tin ti cho ra tn s pht.
+> Khuch i ra anten: C nhim v: - m bo cng sut bc x ra khng gian.
- Lc hi bc cao.
- Phi hp tr khng.
tng hiu qu ca vic pht sng v tuyn in ngi ta a ra s khi phc tp
hn nh sau:
trang:3
Dao ng iu ch
K tintc
K raanten
Ngun tin
-
8/3/2019 Bai Tap Lon Mon Thu Phat
4/26
BI TP LN MN THIT B THU PHT V TUYN IN
+> Khi tng hp tn s v to tn s pht: C nhim v to ra nhiu tn s pht theoyu cu t tn s chun ca b dao ng thch anh.
+> Tin khuch i cng sut: C nhim v khuch i bin tn hiu t khi iu
ch ti c bin ln trc khi bc x ra khng gian.
+> Khuch i cng sut: C nhim v lc hi, phi hp tr khng vi mch ra Anten.
3. Phn loi my pht:
C nhiu cch phn loi khc nhau tu theo mc ch s dng
a.Phn loi theo nhm cng tc c cc loi sau:
- My pht lin tc: Cc sng siu cao tn lun lun bc x ra khng gian.
- My pht khng lin tc: Ch bc x ra khng gian khi c tin tc.
b.Phn loi theo tn s pht:
Trong di tn v tuyn in ngi ta chia ra cc di tn:
-sng di: 30KHz 300KHz.
-Sng trung: 300KHz 3000KHz
-Sng ngn: 3MHz 30MHz
-Sng cc ngn: 30MHz 300MHz
-Sng siu ngn: 300MHz 3000Mhz
-Sng SHF: 3GHz 30GHz
Theo cch ny ta c my pht sng trung, sng ngn, sng cc ngn.
trang:4
T/Htn sto
tn s
K/tintc
iu
ch
K/ra
anten
TinK/cng
sut
K/cng
sut
Daongthch
anh
Ngun tin
-
8/3/2019 Bai Tap Lon Mon Thu Phat
5/26
BI TP LN MN THIT B THU PHT V TUYN IN
c.Phn loi theo cng sut pht bao gm:
-Cng sut thp.
-Cng sut trung bnh.
-Cng sut ln.d.Phn loi theo phng php iu ch gm:
- iu bin
- iu tn
- iu fa
- Kt hp
- Xung
4. Cc ch tiu k thut ca my phta. Ch tiu v in:
+ Cng sut pht ca my pht: l cng a ra anten bc x ra khng gian. Cng
sut ny quyt nh c li thng tin ca thit b gi l cng sut c ch P t. Cng sut tn
hao Pa, cng sut tiu th P0 (tiu th nng lng ca ngun ).
+ Hiu sut ca my pht:
0
tP
P
=
2% 20% =
+ Di cng tc: L kh nng lm vic ca my pht (bc x ra anten) trong mt di tn
s, on tn s no .
+ n nh tn s pht: y l ch tiu quan trng nht ca my pht n m bo
c qu trnh thng tin lin lc nhanh chng, thu hp c rng di tn khng gy
can nhiu cho cc i pht khc. n nh tn s ph thuc ch yu vo tng to dao
ng ch ca my pht do nng cao n nhca tn s dao ng ch ngi ta
dng thch anh.
+ chnh xc ca tn s: L s sai lch gia b ch th tn s pht vi tn s bc x
thc t ca anten ca my pht ra khng gian. N ph thuc vo c cu ch th ca
my pht :
trang:5
-
8/3/2019 Bai Tap Lon Mon Thu Phat
6/26
BI TP LN MN THIT B THU PHT V TUYN IN
+ Sng hi: L cc tn s hi bc x ra khng gian cng vi thnh phn tn s c bn
ca my pht, tn s hi s gy nhiu cho cc i pht khc v gy nhiu cho i xung
quanh.
+ Tham s iu ch gm:+/ Di tn iu ch: L gi tn s thc hin iu ch tin tc trong my pht. Tu theo
tng loi tin tc m s dng tn s iu ch thch hp.
+/ Phi m bo su iu ch: Tc l s dng di tn v tn s thch hp, thng s
dng cho phng php iu ch n bin.
+/ c tuyn tn s iu ch: ng cong biu din s ph thuc h s iu ch theo
tn s.
+/ Mo phi tuyn iu ch:Mo phi tuyn do tnh cht phi tuyn ca cc phn t phi tuyn gy nn. Mch khuch
i c c im l chn p tp m nn ta da vo trit tiu cc thnh phn khng
c li. Trong mch khuch i h s khuch i cng khng ng u vi cc tn hiu
khc nhau.
b. Cc ch tiu k thut v kt cu:
Ph thuc vo iu kin, mc ch s dng thit b ngi ta xt n ch tiu:
+/ Trng lng th tch+/ Kh nng chu va p
+/ Kh nng chu nhit , m
+/ Thun li cho vic thao tc s dng
+/ H s an ton c kh ca thit b
+/ Gi thnh ca thit b
trang:6
-
8/3/2019 Bai Tap Lon Mon Thu Phat
7/26
BI TP LN MN THIT B THU PHT V TUYN IN
II. My thu
1.Cc tham s k thut
a. nhy trong my thu:
nhy l kh nng thu c tn hiu nh nht u vo m my thu cho ra c mctn hiu tin tc b ch th bnh thng. y l ch tiu quan trng nht nh gi
cht lng ca my thu. nhy ph thuc rt ln vo cc tng u vo v ph thuc
vo h s phm cht ca cc linh kin. n v nh gi nhy l mv hoc v
b. n nh tn s:
n nh tn s ca my thu c nh gi bng di tn f ca my thu, f cng
nh th n nh tn s cng cao.
c. chnh xc ca tn s:c nh gi bng sai lch tn s gia tn s trn b ch th ca my thu v tn s
cng hng u vo ca my thu .
d. Di tn cng tc:
Di tn cng tc l thng s nh gi kh nng lm vic ca my thu trong mt on
tn s cng tc nht nh.
e. Ch cng tc:
Ch cng tc l kh nng my thu c th thu c cc loi tn hiu cc ch iuch khc nhau.
f. Ngun cung cp:
Ngun cung cp gm in p s dng, cng sut ngun tiu th.
Ngoi ra cn mt s thng s khc nh kch thc, kt cu lm vic,nhit , m.
2.Phn loi my thu
a. Phn loi theo di tn s cng tc gm:
+ My thu sng di
+ My thu sng trung
+ My thu sng ngn
+ My thu sng cc ngn
+ My thu sng siu cao tn
trang:7
-
8/3/2019 Bai Tap Lon Mon Thu Phat
8/26
BI TP LN MN THIT B THU PHT V TUYN IN
+ My thu ton sng
b. Phn loi theo ch thu gm:
+ My thu iu bin: gm my thu n bin v my thu a bin
+ My thu iu tn+ My thu iu pha
c. Phn loi theo tn hiu tin tc gm:
+ My thu hnh
+ My thu thanh
+ My thu ch(Telex)
+ My thu nh
+ My thu Fax3. My thu khuch i thng:
+ Mch vo l khung cng hng cng hng tn s cn thu, thng l khung daong LC.
+ Khi tch sng: tch tn s cn thu ra khi tn s cao tn.
+ Khi khuch i cng sut: Khuch i bin tn hiu thu ln a ra loa.
Nhc im ca my thu ny l: n nh km, di tn lm vic hp, tp m ln v
nhiu.
u im: n gin, r tin, khng i hi cng ngh.
4. My thu i tn:
trang:8
Tchsng
Mchvo
K/cngsut
-
8/3/2019 Bai Tap Lon Mon Thu Phat
9/26
BI TP LN MN THIT B THU PHT V TUYN IN
+ Mch vo: C nhim v chn lc tn s cn thu. Tn hiu c chn a vo khi
K/ cao tn, y khng quan trng h s khuch i m iu quan trng l t s S/N.
+ Khi i tn: Trn tn s t khi khuch i cao tn vi tn s khi dao ng ni
OSC a ra tn s khng i Ftt tn s ny c a qua khi khuch i na, tng
khuch i ny quyt nh nhy ca my thu.
+ Khi tch sng: Phc hi li tin tc a vo b khuch i cng sut a ra loa,tch mt phn tn hiu a vo b t iu chnh khuch i.
+ Mch t iu chnh khuch i c nhim v bo m tn hiu n b tch sng l
ln v trong gii hn b tch sng c hiu qu. B t iu chnh khuch i thc
hin iu ny bng cch cm nhn mc tn hiu u vo ti b khuch i cao tn,
cng nh tn hiu vo b khuch i tin tc v iu chnh h s khuch i ca b
khuch i duy tr n mc n nh.
trang:9
K/cao tn
itn
K/trungtn
OSC
Tchsng
K/cngsut
AGC
Mchvo
S khi
-
8/3/2019 Bai Tap Lon Mon Thu Phat
10/26
BI TP LN MN THIT B THU PHT V TUYN IN
PHN II. PHN TCH S KHI,S TNG PHI HP TR KHNG
ANTEN CA MY THU PHT VT JSS-720
I. Phn tch phn pht1. Khi pht ca JSS 720 bao gm cc khi:
+ Khi to tn hiu n bin SSB
+ Khi tng hp tn s v to tn s pht
+ Khi khuch i cng sut
+ Khi iu hng Anten
2. Nhim v cc khi:
+ Khi to tn hiu n bin SSB: Tn hiu ny c to ra bng cch iu ch tn hiuAF( tn hiu m thanh) vi tn s sng mang 455kHz. N c dng cho mch bin i
tn s bin i thnh tn s pht.
+ Khi khuch i cng sut: Khuch i bin tn hiu ln a ra Anten, loi
b tp m ra khi tn hiu.
+ Khi iu hng Anten: C nhim v bc x tn hiu ra ngoi khng gian, phi hp
tr khng vi tng khuch i cng sut.
3. Phn tcha, Khi to tn hiu n bin SSB
Dao ng thch anh to ra tn s 20MHz sau c a qua b chia 4 v a vo
mch vng kho pha PLL to ra tn s 455kHz.
+ Nguyn l to tn s 455kHz bng mch vng kho pha PLL.
S khi mch vng kho pha:
trang:10
-
8/3/2019 Bai Tap Lon Mon Thu Phat
11/26
BI TP LN MN THIT B THU PHT V TUYN IN
Khi khng c tn hiu vo th tn hiu hiu chnh Ud =0 v tn hiu ra ca b tch sng
pha l tch (Uv x Ud ). Mch VCO dao ng ti tn s dao ng ring f = 455kHz. Khic tn hiu vo b tch sng pha s so pha tn s tn hiu vo vi tn hiu so snh. u
ra ca b tch sng pha xut hin tn hiu Ud m tr s tc thi ca n t l vi hiu pha
(hiu tn s) ca hai tn hiu vo thi im ng thi c cc thnh phn tn sfv fr
v fv + fr . Tn s tng b loi b nh mch lc thng thp cn tn s thp c
khuch i ln v c dng iu khin tn s dao ng ca VCO. Tn s dao ng
ca VCO c thay i sao cho fv fr tin ti 0 ngha l fv = fr hoc fr =N fv vi N
l h s chia ca b chia tn. y fv = 5MHz vy h s chia6
9110N= . Tn s 455kHz
c trn vi tn s AF ( tn s m thanh) to ra tn hiu n bin SSB.
455kHz
trang:11
Lc thngthp vK/
MchChia tn
VCO (f0)
fv
fr
tn hiu sai s
Ud
fr
Ud
fr
f
SSB
Uv , fv
-
8/3/2019 Bai Tap Lon Mon Thu Phat
12/26
BI TP LN MN THIT B THU PHT V TUYN IN
Tn hiu d liu t b iu khin qua cng COM c khuch i m bo bin
tn hiu ln sau a vo b chuyn mch m tn (AF SW). CPU s iu khin
chuyn mch pht i cc tn hiu d liu v cc tn hiu ph: Tone, Alarm, Fs-In.
Tn hiu ra t chuyn mch AF c a ti b iu ch n bin (LSB MOD) iu ch vi sng mang fc = 455kHz to tn hiu SSB. Tn hiu sng mang fc to ra t
b dao ng ch bng thch anh DTCXO 20MHz. Tn hiu sau iu ch a qua b lc
bng (BPF) ly mt di bin tn. Qu trnh iu ch n bin ny nhm mc ch:
+ Gim rng di tn i mt na.
+ Cng sut ca my pht gim.
+ Tp m u thu gim do bin tn ca tn hiu hp hn.
B iu ch nhiu ch (VCA) xc lp ch lm vic ca my pht, c iuchnh bi tn hiu Gain-Cont t CPU. B iu ch ny thc hin iu ch tn hiu n
bin t b lc bng a ti vi sng mang chun fc = 455kHz to ra tn hiu sng
mang ph vi tn s 455kHz.
m bo cht lng ca tn hiu ngun nh:
+ Lc b tn s nh
+ m bo su iu ch
+ Gim nh yu cu vi cc mch lc,
b, Khi tng hp tn s v to tn s pht
Tn hiu mang tin tc c tn s 455kHz s c a ln tn s sng mang rt cao, vic
ny c thc hin nh cc b trn (MIX). u tin tn s sng mang 455kHz c
trn vi tn s fL1 = 70MHz to ra tn s 70.455MHz. Sau khi c khuch i v
qua b lc bng a ti b trn th hai, ti y n c trn vi tn s fL2 to tn
s pht f0. Tn s fL2 bin i trong mt khong t 70.055MHz n 97.955MHz lm
cho f0 bin i trong di tn t 1.6MHz n 27.5MHz. y chnh l di tn lm vic
ca my pht. Tn s fL2 ph thuc vo cc h s chia M,N ca cc b vng kho pha
(PLL).
trang:12
-
8/3/2019 Bai Tap Lon Mon Thu Phat
13/26
BI TP LN MN THIT B THU PHT V TUYN IN
Tn s f0 sau khi qua b lc c a ti khi khuch i cng sut to cng
sut ln a ra Anten..
c,B khuch i cng sut gm:4 khi chc nng:
+ Tin khuch i (DRIVE AMP): Khng yu cu v h s khuch i m ch lm tngt s tn hiu trn tp m (S/N).
+ B chia tn hiu (POWER SPLITTER): Chia tn hiu t b tin khuch i thnh ba
ng tn hiu ring bit ti 3 b khuch i cng sut.
+ Cc b khuch i cng sut: Thc hin khuch i cng sut. Cc mch ny m
bo h s khuch i a ra cng sut ln.
+ B tng hp cng sut(POWER COMBINER): Tng hp cng sut t 3 b khuch
i cng sut.Mc ch ca vic s dng ba b khuch i cng sut ring r trong khi khuch i
cng sut l gim bt yu cu v h s khuch i, kh nng chu ti, phm cht
ca cc phn t khuch i do lm gim gi thnh thit b.
Tn hiu sau khi khuch i vi cng sut ln s c a ra Anten bc x
ra khng gian. phi hp tr khng gia anten v b khuch i cng sut phi dng
mch phi hp tr khng. Mt khc, my pht lm vic nhiu tn s khc nhau, Anten
ch lm vic vi mt tn s cng hng ring nh vy i hi phi c mch ra Anten b cc thnh phn cm hoc dung m bo cho anten lun lm vic ch cng
hng. B phi ghp Anten (ANTENNA TUNER) thc hin cc yu cu trn ca my
pht.
d,ANTENNA TUNER gm cc thnh phn sau:
+ SENSOR: y l t hp nhiu IC c xy dng t nhng mch thut ton, triger,
cc phn t tch cc, cm bin c nhim v so snh pha ca tn hiu dng v p nhm
pht hin s sai pha.
+ AUTOMATIC ANTENNA TUNER: Da trn s sai pha gia dng v p nhn c
t SENSOR t ng iu khin s phi ghp cuae anten anten lm vic ch
cng hng.
trang:13
-
8/3/2019 Bai Tap Lon Mon Thu Phat
14/26
BI TP LN MN THIT B THU PHT V TUYN IN
II. Phn tch phn thu
* S NRD-740
1. Phn thu gm cc khi:
+ Mch vo
+ Mch K/ cao tn
+ Mch i tn
+ Mch K/ trung tn
+ Mch tch sng
+ Mch khuch i cng sut2. Nhim v cc khi:
+ Mch vo: c nhim v chn lc tn s cn thu. Tn hiu c chn a vo khi
K/ cao tn, y khng quan trng h s khuch i m iu quan trng l t s S/N.
+ Khi i tn: trn tn s t khi khuch i cao tn vi tn s khi dao ng ni
a ra tn s khng i Ftt tn s ny c a qua khi khuch i na, tng khuch
i ny quyt nh nhy ca my thu.
+ Mch K/ trung tn: Khuch i tn hiu ln.+ Khi tch sng: Tch tn hiu cn thu ra khi sng mang cao tn.
+ Khi khuch i cng sut: Khuch i cng sut tn hiu ln a ra loa.
3.Phn tch
Tn hiu t anten i vo my thu, trc tin n i qua mch TEST th xem my
sn sng lm vic cha, sau c a qua mch bo v ARRESTER v
BKRELAY mch ny c tc dng bo v my thu khi m tn hiu t my pht ln c
a ti anten nhng khng vo my thu do lc ny rle c ngt ra khi anten. V
my thu lm vic di tn rt rng do m bo nhy my thu mch vo ca
my thu ngi ta chia thnh 8 mch vo di rng, khi cn thu on tn s no mch
iu khin s ng mch vo tng ng vi on tn s , ng m cc mch vo
ta s dng chuyn mch bng diot.
trang:14
-
8/3/2019 Bai Tap Lon Mon Thu Phat
15/26
BI TP LN MN THIT B THU PHT V TUYN IN
- S chuyn mch s dng diot:
Bnh thng ta cp cho catt ca hai diot mt in p m hoc l 0V do cc
diot khng thng nn mch vo ng, khi cp in p dng cho catot hai diot thng
nn mch vo m cho tn hiu i qua ( ngi ta tnh ton sao cho bin in p cu
tn hiu vo phi nh hn bin in p mt chiu cp cho catot ca diot). Tn hiu t
chuyn mch diot c a vo b lc thng thp 35MHz mch lc ny ch cho qua tn
s nh hn hoc bng tn s 35MHz, sau c a ti mch khuch i cao tn
mch ny ch c tc dng nng cao t s S/N.
Tn hiu ra ca b khuch i cao tn c trn ln th nht vi tn s dao ng
ni(70.455 ~ 100.454999MHz) t b dao ng LOOP1 tn hiu sau b trn c a
vo mch lc c tn s 70.455MHz, vic chn lc tn hiu cn thu do dao ng
ni t LOOP1 tn s ny qua b khuch i trung tn loi b tn s nh ng thi
chng nhiu-pha inh sau c trn ln th hai vi tn s 70MHz t LOOP2 a tn
s trung tn cao xung thp tr v tn s ban u 455KHz, tn hiu i tip qua rle, qua
mch lc thng thp 455KHz c di thng 12KHz.
trang:15
D2
Ur
L
C1
D1
Uv
C2
-
8/3/2019 Bai Tap Lon Mon Thu Phat
16/26
BI TP LN MN THIT B THU PHT V TUYN IN
ng thi tn hiu 455kHz c a vo mch lc tp m. Tip theo tn hiu c a
vo b lc bng gm 4 di tn: 0.3KHz, 1KHz, 3KHz, 6KHz. Tn hiu 455KHz a
qua 4 b khuch i trung tn ( bn b khuch i trung tn ny nhm tng h s
khuch i v tng nhy ca my thu) tn hiu ra t b khuch i trung tn th ba i
qua mch khuch i sng mang (CAR AMP) i vo b gii iu ch (DEMO) cng
vi tn hiu t b khuch i trung tn th ba. Tn hiu gii iu ch c a vo b
SQLMUTE qua b iu chnh to nh (volume) iu chnh tn s theo mun v qua b
khuch i m thanh a ra loa.
+ LOOP1: To dao ng ni quyt nh tn s cn thu, to tn hiu TESTL1.
+ LOOP2: To ra tn s dao ng ni th hai, to ra tn hiu TESTL2.
+ CPU: iu khin qu trnh lm vic ca cc khi trong my thu.
trang:16
455KHz
12Khz
-
8/3/2019 Bai Tap Lon Mon Thu Phat
17/26
BI TP LN MN THIT B THU PHT V TUYN IN
III. i su phn tch b phi hp tr khng anten JSS-720.
1. Khi qut:
mt trong nhng yu t quyt nh n cht lng ca my pht l vic phihp tr khng gia tng KCS v anten anten c th bc x tt nht sng in t
ra khng gian. khi anten lm vic ch cng hng.
nu my pht s dng mt tn s th ch cn s dng mt anten pht. do nu
my pht s dng nhiu tn s pht th my pht s phi s dng nhiu anten
pht nn s gy lng ph v cng knh.
Vn t ra l s dng my pht nhiu tn s ch s dng mt anten pht khc
phc nhc im trn chnh l phng php m rng di tn lm vic ca antenpht hay iu hng anten pht.
khc phc nhc im trn ngi ta s dng mt mch ghp anten mch ny
ghp gia tng khuych i cng sut v anten.
s khi:
trang:17
-
8/3/2019 Bai Tap Lon Mon Thu Phat
18/26
BI TP LN MN THIT B THU PHT V TUYN IN
S tng ng ca anten:
T s tng ng ca anten ta nhn thy rng anten gm c ba thnh phn:
phn cm LA , thnh phn in dung CA , v thnh phn tn hao RA
trong ba thnh phn trn th thnh phn RA khng ph thuc vo tn s ch c hai thnh
phn LA v CA lph thuc vo tn s t vo anten.
Tr khng ca anten l:
ZA=RA + j(XL XC)
trong
CX
LX
A
A
C
L
1=
=
Khi anten cng hng tn s 0 th ta c:
LC
XXAA
CL
1
0==
=
Khi cng hng th anten bc x cng sut ra khng gian l ln nht
khi lch tn s cng hng ring ca anten 0 th khi anten c th mang tnh
dung hoc tnh cm khi anten bc x cng sut ra khng gian thp. trong trng hp
ny mch ghp s c tc dng b thnh phn cm nu anten mang tnh dung v b
trang:18
-
8/3/2019 Bai Tap Lon Mon Thu Phat
19/26
BI TP LN MN THIT B THU PHT V TUYN IN
thnh phn dung nu anten mang tnh cm anten c th cng hng vi bt k thnh
phn no ca tn s pht.
mch ghp anten gi l tng ra ca my pht.
Mch ra yu cu phi m bo cong sut ra v hiu sut ra cao. hiu sut ra ca mch ras quyt nh hiu sut ca ton my pht v cng sut ca tng ra chim 90% cng sut
ton my pht.
iu khin cc mch ra ny thi trong my thu pht JSS-720 ngi ta s
dng cc b vi iu khin v cc cm bin v pha cm bin v
ti cm bin v t s sng ng.
Sau y ta s phn tch cc b cm bin s dng trong my thu pht JSS 720.
2.S khi ca b iu hng:
B iu hng anten gm cc b phn chnh sau:
+ Mch cm bin
+ Mch iu khin
+ Mch bo v
+ Mch phi hp tr khng
Trong khun kh bi tp ln ny ta s ch phn tch chi tit mch cm bin
(sensor) ca b phi hp tr khng.
Mch cm bin bao gm cc b cm bin : cm bin pha ,cm bin SWR (Standing
Ware Ratio), cm bin tr khng ti.
trang:19
Cm bin Mch phi hp
iu khin Bo v
Kim tra dnganten
anten
NFC 801/802
-
8/3/2019 Bai Tap Lon Mon Thu Phat
20/26
BI TP LN MN THIT B THU PHT V TUYN IN
a, B cm bin v pha (phase sensor )
s khi ca b cm bin pha:
trang:20
-
8/3/2019 Bai Tap Lon Mon Thu Phat
21/26
BI TP LN MN THIT B THU PHT V TUYN IN
v nguyn tc so snh pha gia dng in v in p th chng ta phi
chuyn v cng mt i lng dng in hoc in p sau a vo so snh. y
ngi ta chuyn v in p, nguyn l hot ng ca cm bin nh sau:
trn ng dy tn hiu dn t my pht ra anten ngi ta t mt cm bin dng, trn
cun th cp ca cm bin dng ta mc mt in tr R1 ly tn hiu in p a vo
chn 4 v 5 ca IC1 nu dng trn ng tn hiu cng ln th in p a vo IC1
cng tng theo( ngoi tr trng hp chp ti khi s khng c dng cun th cp
ca bin p dng) IC1 c tc dng so snh in p cm bin c t cm bin dng vi
mt mc in p ngng nht nh. khi in p vo ln hn mc ngng th in p ra
chn 15 ca IC1 s mc thp ngc li th cho ra mc cao.
ly pha ca in p ngi ta trch mt phn in p t ng tn hiu qua mch
phn p vi cc thnh phn R10, R11, R12, R18 v t C23 v a vo chn 4 v 5 ca
IC4. IC4 hot ng cng tng t nh IC1.
trang:21
-
8/3/2019 Bai Tap Lon Mon Thu Phat
22/26
BI TP LN MN THIT B THU PHT V TUYN IN
u vo ca IC1 v IC4 c mc thm cc t C1 v t C24 ngn mch thnh phn
cao tn. Cc dit CD2 v CD4 c tc dng nh mt mch ghim mc 0v, cc it CD3
v CD1 bo v qu ti cho IC1v IC4 tc l khi in p cm bin ln hn 5v th it
CD1 v CD3 thng v s hn dng vo IC.Vic so pha c thc hin nh D plipplop:
tc l u ra ca IC1(chn 15 ) a vo chn D ca plipplop cn u ra ca IC10 a
vo chn CE (Chip Enable ) ca plipplop.
mc in p u ra ca IC3 s cho bit tr khng ca mch ra anten mang tnh cm hay
tnh dung.
Nu in p u ra IC3 mc cao th s mang tnh cm.
nu in p du ra ca IC3 mc thp th tr khng s mang tnh dung.in p ny s c bin i A/D ri a v vi x l.
Ngoi tn hiu so pha th vi iu khin cn a ra tn hiu tt b so pha (phase sensor
off ) bnh thng tn hiu ny mc thp th b so pha hat ng bnh thng nhng
khi n c a ln mc cao th s lm cho Transistor TR3 thng, TR1 v TR2 kho
lm cho in p u vo IC4 rt nh dn ti u ra 15 mc tch cc cao lm cho chn
CE (Chip Enable ) ca D plipplop cng mc cao nn lm cho D plipplop ngng lm
vic.b, B cm bin t s sng ng (SWR ) :
Khi khng phi hp tr khng gia tng PA v Anten, th c sng phn x. S
phn x nhiu hay t c c trng bi t s song ng SWR-Standing Wave Ratio.
S mch:
trang:22
-
8/3/2019 Bai Tap Lon Mon Thu Phat
23/26
BI TP LN MN THIT B THU PHT V TUYN IN
Mch ny lm nhim v cm bin v t s in p sng ng SWR(bng cch so
pha ca dng pht i v dng phn x) thng qua hai tn hiu Vf v Vr. Trong Vf l
tn hiu a ra tng trc(sng pht i; Vr l tn hiu phn hi v tng sau(song phn
x).
Cm bin Vf: tn hiu ra anten qua cm bin dng T2 chuyn t dng thnh p i
qua diode CD5 , so snh tn hiu cm bin v in p ly t C11 v C13.vi tn hiu
trang:23
-
8/3/2019 Bai Tap Lon Mon Thu Phat
24/26
BI TP LN MN THIT B THU PHT V TUYN IN
cm bin o pha ly t bin p dng T2.Tn hiu ny c ua dn b so snh
IC5A thng qua R22,L59.
Cm bin Vr: tn hiu ly t diode CD5.CD5 so snh tn hiu cm bin v in
p ly t C12 v C14.vi tn hiu cm bin o pha ly t bin p dng T2.Tn hiu
ny c ua dn b so snh IC5B thng qua R23,L60.
C9,C10,R33,R34,C59,C60 lm nhim v lc thnh phn bin i.
Sauk hi i qua IC5A v IC5B tn hiu s c ly ra t chn 7&1 ca 2 IC ny
v chng c a ti vi x l thng qua 2 mch lc bao gm C39,L53,C33(v
C41,L55,C35).
c, B cm bin ti (LOAD):
S mch:
trang:24
-
8/3/2019 Bai Tap Lon Mon Thu Phat
25/26
BI TP LN MN THIT B THU PHT V TUYN IN
Mch bao gm cm bin dng T3,diode CD7 ,CD8; in tr R26~R31; t in
C16~C20; cun cm L7~L9.B cm bin ny s cm bin v cho ta bit v tr khng ca anten (ti)
nguyn l ca b cm bin ny l n so snh v ln ca dng v p ra anten.
hot ng ca mch nh sau:
u ra ca cun th cp ca bin p dng s c mc vi in tr R27,
R26 ly p in p ny s c nn ly in p 1 chiu a vao b so snh IC3.
Trn ng dy tn hiu ngi ta trch ra in p v qua dit nn ly in p mt
chiu a vao chn o ca b so snh.
u ra ca b so snh s cho bit tr khng ca anten ln hn 50 hay nh hn 50
.
Nu chn load mc cao th tr khng ca anten nh hn 50 .
Nu chn load mc thp th tr khng ca anten ln hn 50 .
trang:25
-
8/3/2019 Bai Tap Lon Mon Thu Phat
26/26
BI TP LN MN THIT B THU PHT V TUYN IN
IV. KT LUN.
Nh vy,qua vic phn tch s h thng ta thy i hi khi lng cc kin
thc tng quan, cch thc lin h gia c s l thuyt v thc tin .Qu trnh phn tchl qu trnh tng hp li cc kin thc cc phng php nghin cu.Yu t nh hng
nhiu trong qu trnh phn tch mt h thng chnh l mt kin thc c bn, khi nm
chc iu trnh t phn tch c p dng l chia nh theo tng khi ,thc hin phn
tch chc nng nhim v ca khi ,ri thc hin lin kt cc khi con trong ton
b h thng c cch nhn tng th nht.
c th gii thch ti sao mch hay khi li lm nhim v g, ti sao dung phn
t ,hay ti sao li s dng gii php ny m khng s dng phng n khc?th ihi ngi phn tch phi mc ni cc phn lin h trn cc nguyn tc c bn,thc hin
pht trin khi c s h tr ca cc linh kin thay th.
Qu trnh phn tch s khi cng nh i su phn tch chi tit mt module c th
trong my v tuyn JSS-720 gip em c c phng php phn tch mt h thng
c chinh xc,nhng r do hn ch v mt kin thc cung nh ti liu tham kho do
khng trnh khi nhng sai st trong qu trnh tm hiu v phn tch, rt mong c
s gp ca thy c v bn b bi phn tch c chnh xc v hon chnh hn.
trang:26