Truyen Hinh Mau

8/12/2019 Truyen Hinh Mau

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L i n i u

Trong x hi hin nay, nhu cu trao i thng tin lun gn lin vi spht trin ca con ng-i. T rt xa x-a loi ng-i c nhu cu trao ithng tin nn vn mong mun c mt ph-ng php truyn thng tin i xa.

Ngy nay, nhng mong -c ca con ng-i tr thnh hin thc. Cngvi s pht trin ca x hi, khoa hc k thut ng mt vai tr rt quantrng. Trong bt k lnh vc hot ng no ca con ng-i cng cn nthng tin. Chnh v vy, trong vi thp k gn y x hi loi ng-i c sbng n v thng tin, loi ng-i ang chuyn sang k nguyn thng tin.Khng ging nh- cc ti nguyn khc, ti nguyn thng tin l v tn, cngkhai thc th cng lm cho thng tin ngy mt phong ph thm. Mt trongnhng lnh vc khoa hc k thut, thng tin cung cp cho cc hot ngca con ng-i l truyn hnh.

Mt trong nhng kha cnh quan trng ca truyn hnh l my thuhnh, cng vi s pht trin ca k thut truyn hnh th my thu hnh cng

pht trin nhanh chng, t my thu hnh en trng n my thu hnh muri n my thu hnh cht l-ng cao... p ng nhu cu ca con ng-ingy cng cao.

Vit Nam cng nh- cc n-c trn th gii, truyn hnh ngy mtpht trin mnh m. Cht l-ng truyn hnh ngy cng mt tt hn, sl-ng thng tin -c truyn ti trn truyn hnh ngy mt phong ph. Spht trin ca truyn hnh -c th hin kh r 3 h truyn hnh mu l:PAL, NTSC, SECAM, c bit l h truyn hnh mu PAL v NTSC.

Trong n tt nghip ny, -c s gip nhit tnh ca cc thyc trong phng k thut trung tm thc hnh in T Vin Thng, cbit l thy gio ThS D-ng Thanh Ph-ng tn tnh gip em nghincu v trnh by n ny.

Em c gng nh-ng v thi gian c hn v s hiu bit v chuynmn cn hn ch nn n ny cn nhiu thiu st v ni dung v hnhthc. Vy em mong cc thy c thng cm v ch bo thm cho em.

n gm 3 phn chnh l:Ch-ng I: Nguyn l truyn hnh muCh-ng II: S khi my thu hnh muCh-ng III: Mch ngun cho my thu hnh

H Ni, ngy 01 thng 04 nm 2007

SV thc hin

Nguyn Minh Hin


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Ch ng INguyn l truyn hnh mu

I. Nguyn l truyn hnh muTrong h thng truyn hnh en trng nh truyn i -c hin th

bng sng ti cc im trn t-ng dng my nh, camera c nhim vbin i sng ti truyn hnh nh nhiu mc in p khc nhau. mbo cho nh thu -c ng b vi nh pht i, ta cn phi pht xung ngb dng v xung ng b mnh. Dng sng ca tn hiu truyn hnh entrng y gm tn hiu hnh, xung xa v xung ng b, v vy trong hthng truyn hnh mu ta phi truyn thng tin v mu ng vi mi imca hnh u t l vi ba mu c bn: mu (R red), mu lc (Ggreen),mu l (B blue) v mu l mu khng cn truyn tn hiu chi. Vvy, dng sng tn hiu truyn hnh en trng gm xung xa, xung ng btruyn hnh v thng tin v chi -c thay th bng truyn hnh thng

tin v tn hiu mu.1. H thng truyn hnh c bnH thng truyn c bn l h thng truyn hnh ng thi truyn ba

tn hiu mu ring bit l tn hiu hnh.a. H thng thit pht tn hiu mu

H thng thit b pht mu

nquangRR

nquangGG

BnquangB

Khuchi KR

i uchFR

Khuchi KG

i uchFG

Khuchi KB

i uchFB

MyphtFov

DR DG DB

D


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Ph ca tn hiu mu

Knh l-ng sc 3, phn chiu mu (R) v truyn i mu lc (G) G-ng phn chiu 2 v g-ng phn chiu 4 phn chiu nh sng

mu l (B) v mu (R).

Do h thng knh l-ng sc v g-ng phn chiu phn tch nhsng mu sc ca cnh vt gm 3 thnh phn c bn -a ti 3 knh lc mu,knh lc mu (R) ch cho mu qua (cn cc thnh phn khc th knhhp th), cc knh lc khc cng t-ng t (knh lc mu B ch cho mu B iqua, knh lc mu G ch cho mu G i qua). nh sng ca 3 mu c bn R,G, B -c -a truyn n n quang in. n quang in c nhim vbin i tn hiu quang (nh sng mu R, G, B) thnh tn hiu in t-ngng vi 3 mu c bn RR, FG, FB. in p tn hiu FR, FG, FB, -c truynti b khuch i in p KR, KG, KB, khuch i tn hiu mu ln ln sau -c -a vo iu ch bin ca 3 tn s mang tn s cao tnFRFGFB, ba tn s sng mang iu bin -c -a n b cng h-ng vta -c tn ph nhtrn.

Nu cc di ph tn hiu l mu D v gii ph ca tn hiu mulc D v gii ph ca tn hiu mu l D u bng 6MHz v dnh thm 1MHz lm khong m gia cc di tn th di thng ca knh truynhnh l:

D = 6MHz * 3 + 1 MHz = 19 MHz.Tn hiu tng hp ca knh truyn hnh mu u ra b cng -c

-a ti my pht. My pht c nhim v to ra tn s sng mang pht hnh

Fov v ly tn hiu tng hp ca knh truyn hnh iu ch bin sngmang Fov cui cng sng iu ch -c -a ti Anten pht, pht rakhng gian d-i dng sng in t.

b. H thng thit b thu muL s khi ca thit b thu tn hiu Anten mu, anten my thu

nhn -c tn hiu cn thu c tn s sng mang Fov qua cc tng khuchi cao tn, i tn, khuch i trung tn v tch sng, ta li ly ra -cgii tn ca knh truyn hnh mu.


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S khi thu mu

Tn hiu ca knh truyn hnh mu -c -a ti b lc khuch ivi b khuch i di ly ring ra 3 tn s sng mang mu iu chFG, FR, FB. Tn s sng mang mu -c -a ti b tch sng ly ra 3 tnhiu mu ring bit R, G, B. Tn hiu mu -c khuch i v cung cp quathu knh v n trn mu trn hnh nh v ti to li cnh vt y mu sc.

Tn s qut dng v qut mnh -c s dng nh- mn hnh entrng.

Kt lun H thng truyn hnh mu trn khng c -ng truyn chi Y

ring bit do khng p ng -c khi thu ch-ng trnh truyn hnh entrng.

Di thng tin ca truyn hnh mu qu rng (19 MHz), do khngph hp vi truyn hnh en trng (di thng khong 60 MHz).

thc hin -c di truyn hnh mu v truyn hnh en trng, taphi to ra -ng truyn chi ring bit v di thng ca tn hiu mu 6MHz ph hp vi di thng ca tn hiu truyn hnh en trng.

II. Tn hiu trong truyn hnh mu1. Tn hiu chi

Tn hiu chi l tn hiu hnh nh trong truyn hnh en trng. hthng truyn hnh mu, tn hiu chi -c t hp t ba tn hiu mu c bnER, EG, EBtheo biu thc sau:

Y = 0,3 ER+ 0,59 EG+ 0,11 EB2. Tn hiu mu

Tn hiu mu l hiu s ca tn hiu mu c bn v tn hiu chi.Trong truyn hnh mu ng-i ta khng trc tip pht i cc tn hiu muc bn m pht i cc tn hiu mu v to nh mu trng cc tn hiu muu bng khng, do khng gy nhiu ln nh en trng.

Ba tn hiu mu:

ER EY= EE (0,3R+ 0,29G+ 0,11EB) = 0,7 ER 0,29 EG 0,11EBEG EY= EG (0,3R+ 0,29G+ 0,11EB) = 0,3 ER+ EG 0,11EB


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EB EY = EB (0,3ER + 0, 9EG + 0,11EB) = 0,3 ER 0, 9 EG 0,89EB

La chn tn hiu mu truyn i trong truyn hnh mu.i truyn hnh mu pht i mt tn hiu chi EYv hai tn hiu in

mu ER EYv EB EY. Tn hiu mu th ba EG EY b khng gi i v:

+ Qung bin thin ca EG EYl nh nht cha l-ng thng tinkm r rng.

+ Mt ng-i rt nhy cm vi mu lc G, c th phn bit cc chi titrt nh do phi gi tn hiu mu lc G vi di ph rng, lm phc tpthm v k thut. Bi vy pha thu phi dng mch ma trn G Y toli tn hiu mu th ba EG EYtheo cng thc sau:

EY= 0,3 ER+ 0,59 + 0,11 EBEY= 0,3 (ER EY) + 0,59(EG EY) + 0,11 (EB EY) + EYEY EY= 0,4 (ER EY) + 0,59 (EG EY) + 0,11 (EB EY)0,59 (E

G E

Y) = 0,3 (E

R E

Y) 0,11 (E

B E

Y)

ER EY= 0,51 (ER EY) 0,19 (EB EY)4. Bin php rt gn di tn rt gn di tn ca tn hiu mu tng hp cho ph hp vi di tn

ca h thng truyn hnh en trng ta da vo 2 yu t sau:a. Kh nng phn di chi tit nh mu ca mtCc th nghim cho rng kh nng phn gii ca mt i vi cc phn

t mu ph thuc vo mu sc ca cc phn t mu. Kh nng phn giica mt tt nht l i vi mu lc G, i vi cc mu c b-c sng >560nm v b-c sng > 500nm kh nng phn gii ca mt gii nhanh. Mu

c ph cng rng th kh nng phn gii ca mt cng cao, v ng-c li. Do mt c phn gii vi mu lc l tt nht, i vi mu mt c phn gii trung bnh, i vi mu l mt c phn gii km.

Thc nghim cho ta bit: i vi tn hiu R hay (R Y) ch cn gii tn c tn s khong

1,5MHz i vi tn hiu B hay (B Y) ch cn di tn c tn s khong

0,5MHzDo di tn ca tn hiu mu tng hp chim 9MHz gm: tn hiu

chi Y chim di tn s 6 MHz v dnh 1 Mhz lm khong m. Trong

nhiu di tn ca tn hiu tng hp ny ch-a kt hp -c vi h thngtruyn hnh en trng.

6MHz 1, MHz 0, MHz

9MHz

fy f(RY) f(BY)


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Di tn ca tn hiu mu tng hpb. Ph-ng php xen tnPh ca tn hiu chi (hay tn hiu truyn hnh en trng) khng lin

tc. Cc vch ph tp trung tn s mnh fv cng vi bi ca n 2fv... nfv

v cc nh ca tn.S dng f.h cng nhng bi ca n, khu vc tn s cng cao th

nh ca chng cng nh dn.Nng l-ng ca tn hiu chi Y tp trung khu vc tn s cng cao

th nh ca chng cng nh dn.Nng l-ng ca tn hiu chi Y tp trung nhng vch nht nh ta

c th ci l-ngThng tin mu vo khong chng gia cc vch c chi. Do 2

tn hiu "mu hiu" (R Y) v (B Y) khng phi truyn i 2 di tn ringbit m ci ngay trong di tn ca tn hiu chi cng truyn i. Vvy m di tn ca tn hiu mu tng hp Y 9 R Y), (B Y) -c thu v di tn ca Y. Vi ph-ng php ny ta gii quyt -c gia truyn hnh entrng v h thng truyn hnh mu.

Di tn ca ph tn hiu mu tng hp theo ph-ng php xen tnKt lun chungQua phn tch phn trn ta thy h thng truyn hnh mu kt

hp vi h thng truyn hnh en trng thc hin cc bin php sau:+ H thng truyn hnh mu truyn i b chi Y (nh- h thng

truyn hnh en trng)

Vi 2 tn hiu "hiu mu", (R Y) v (B Y) iu ch trn 2 tns sng mang f (R Y) v f ( B Y).

+ Hai tn s sng mang ph f (R Y) v f ( B Y) -c ci vo tnhiu chi Y theo ph-ng php xen tn.

Vn cn li l:+ Thng tin tn hiu mu ch-a -c tp trung i tn khu vc tn

s cao ca di tn dnh cho tn hiu chi Y nu c nh h-ng ln hnhnh.

+ Khi -a tn s sng mang mu ph f (R Y) v f ( B Y) v tnhiu mu t hp d sinh ra giao thoa gia 2 tn s mang mu ph vi tn smang hnh foa, tn s sng mang hnh foa to ln nhng tn s nhiu rtkh loi tr.

01 2 3 4 6

6,2 MHz

01 2 3 4

4,25 MHz


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+ gi i quy t nhng nh-c i m ny m i h th ng truy n hnhphi c nhng bin php gii quyt khc nhau.

III. c im ca h truyn hnh mu1. H truyn hnh mu NTSCNTSC (National televesion committee) y ban h thng truyn quc

gia. y l h truyn hnh u tin trn th gii (nm 1953) ti M do FFCchnh thc ph chun lm h truyn hnh mu ca M.

a. Tn hiu chi Y -c tnh theoY = 0,30 R + 0,59 G + 0,11 B

C rng di tn l 4,2 MHzb. Hai tn hiu "hiu mu": -c truyn ng thi sang pha thu.

Thng tin mu -c truyn i trong h NTSC khng phi l (R Y) v(B Y) m l tn hiu I v Q)

th biu th vect muTrong h NTSC ta chuyn h trc ta (R Y) v (B Y) thnh h

trc ta I v Q lch vi h trc (R Y) v (B Y) mt gc 330. Tn hiumu I v Q -c tnh theo cng thc:

I = 0,74 (R Y) 0,27 (B Y)Y = 0,48 (R Y) 0,41 (B Y)

Tn hiu I c rng di tn l 1,5 MHz v Q c rng l 0,5 MHzHai tn hiu ny -c iu ch vung gc trn mt tn s mang muph fc. Ngha l tn hiu I v Q cng iu ch bin trn cng mt tn sfcnh-ng dch pha 900.

c. iu bin nnTrong truyn hnh en trng cng nh- truyn hnh mu i vi tn

hiu iu bin ta khng truyn i c sng mang F0v c hai di bin tn

trn d-i (F0F) m tit kim ph tn ta ch truyn sng mang vi tondi bin tn trn (f0+ F) v mt phn bin tn d-i. Trong h NTSC cngvy tn hiu I v Q cng -c iu ch vo tn s sng mang f

cnh-ng ta

khng truyn i sng mang m ch truyn i hai di bin tn trn v d-i

E1 M

EQ33

33

ER EY

(05)MHz

EQ

E1

EB EY

(01,5)MHz

(01,5)MHz


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ph-ng php ny gi l truy n thng tin sng bin trit t n s sng mang Imv Qml tn hiu sng bin ca I v Q.

Ph tn hiud. Tn hiu ng b muDo tn s fcli nn hon ton, bn pha pht khng truyn sang pha

thu phc hi, v vy my pht phi truyn i tn hiu ng b mu mythu phc hi tn s sng mang mu fcng tn tn s v phan ban u nh-pha pht. Tn hiu ng b mu c tn s mang mu bng fc= 3,58 MHzv -c t pha sau cc xung dng.

e. Ph ca tn hiu mu tng hpPh ca tn hiu mu tng hp trong h NTSC bao gm chi Y v

sc C, sc C gm tn hiu I iu bin vo tn s fctruyn i ton di bintn d-i v mt phn di bin tn trn tn hiu Q iu bin vo cng tn sfcnh-ng dch pha 900truyn i c 2 bin tn trn v d-i. Hai tn hiu Imv Qmto thnh tn hiu mu sc C;

C = Im+ Qmf. S m ha h NTSC

Hnh 10. Ph ca tn hiu mu tng hp

f0fmax f0 f0+ fmax f0fmax f0 f0+ fmin f0+fmax f0 f0+ fmax

3, 8

3,

Im

Qm

Y

0

MHzfc 43

Matrn

Dy tr

SAMI

SAMII

Bcng

I

Bcng

II

Bcng

C ngmu

U2(t)

0

fH

U4(t)U3(t)

90

U2(t)

U1(t)EREY

EYER

EG

EB

VideoNTSC Ura

EB


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S m h NTSC

Nguyn l lm vic+ Tn hiu mu c bn qua ma trn -c bin i u ra in p chi

EYv in p mu Er, Eb, in p chi qua dy tr gi chm 0,7 ms chong b vi tn hiu mu khi tn hiu mu qua b m ha. Cn 2 in pmu -c -a n b iu ch SAM I v SAM II. Nguyn l 2 b iu chny hon ton ging nhau ch khc nhau ca dao ng sng mang mu:

SAM I l 900, SAM II l 00.Mch to dao ng c f = 3,58 MHz -c di pha t 00sang 330kt

hp vi tn hiu EQcho vo mch iu bin nn loi b sng mang.n b iu ch c dao ng sng mang pht ra in p.Us(t) = Us* sin Wst(ly Us= 1 n v)

Us(t) = Sin Wst+ Xt SAM I: in p ra sau SAM I:U1(t) = Er* cos (Wst)U1(t), U2(t) -a vo b cng I

U3(t) = U1(t) + U2(t)= Er* cos Wst= Eb* sin WstU3(t) v EY-c cng b cng II ta -c U4tU4= EY+ Erc Wst+ Ebsin WstU4(t) v U5(t) qua b cng III ta -c tn hiu Ura(t):y chnh l tn hiu VIDEO iu ch vi dao ng sng mang mug. S gii m mu h NTSC* S

ER EG EB


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Nhim v cc khi+ Tch sng ng b: tch ly 2 tn hiu video l tn hiu mu iu

ch vi sng mang mu v tn hiu chi EY+ Trn 2 tn s trung tn hnh v ting ly ra tn s trung tn ting

tt hn: (4,5 MHz; 5 MHz; 5,5 MHz).

nph

ntin

g


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+ Kh i khu ch i trung t n mu: nng cao bin tn hiu v pht

trin tnh lc tn s cho tn hiu mu trong di tn f = 2,35 MHz 4,2MHz.+ Khi tch sng ng b I, II tch ly tn hiu mu t sng mang

mu.

+ B lc I, II: lc b tn s cao tn fs, gi li tn hiu mu ERYvEBY+ Mch ma trn: bin i tn hiu EY, EG, EB(ma trn ny gm hai

ma trn: ma trn G Y v ma trn RGB).+ Dao ng thch anh (f = 3,58 MHz)+ Cng mu: khuch i xung ng b m i qua. N ch m khi c

xung ng b dng i qua.

Nguyn l lm vicTn hiu tng hp gm 7 tn hiu trong 1 tn hiu ting v 6 tn

hiu th tn (tn hiu xung ng b mnh, ng b dng, tn hiu chi, 2 tin

tc mu l EI, EQ, tn hiu ng b mu. 1 -ng tn hiu chi i qua mch gi chm 0,7mSECAM ch tn

hiu mu qua cc mch n ma trn khi b lch pha. 1 -ng tn hiu qua khuch i trung tn mu khuch i chn

lc, chn ly tn hiu iu bin nn vung gc 2,38 4,2 MHz n y tnhiu vo hai mch tch sng iu bin nn I v tch sng iu bin nn 2ri i vo mch ma trn. Mun c tch sng iu bin nn phi c sngmang mu ph fsc= 3,58 MHz dao ng ny -c xc nh bi pha ca tnhiu le mu. Mch le mu l mt tng khuch i ch m khi c xung tn

s dng fHi vo ngay ti thi im thm sau ca xung ng b dng. Nh-vy u ra ca cng le tt c cc tin tc ca tn hiu khc b loi b, trtin le mu vi pha 00 -c -a ra kch thch tng dao ng OSC fsc,sng mang ph -c quay sm pha +330-a vo tch sng iu bin EQ,ri li quay sm pha 900na tch sng iu bin EI.

Kt lun v h mu NTSC Truyn ng thi 2 tn hiu iu bin sng mang ph fsc(3,58 MHz hoc 4,43 MHz) bi 2 tn

hiu mu EI, EQbng cch iu bin nn vung gc.

Tn hiu mu NTSC c cha 7 tin tc:+ 4 tin tc u ca truyn hnh en trng: gii tn n 4,5 MHz(FFC)

+ 2 tn hiu mu EI gii tn t 0 1,2 MHz, EQ c gii tn t

00,5MHz -c chn vo bin trn ca tn hiu chi t 2,38 MHz n4,2MHz

+ Tn tc th 7 l le mu (ng b mu) Le mu truyn i pha gc 0 ca sng mang ph, dng chun

pha sng mang ph fsc my thu cn cho tch sng iu bin nn vung

gc


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B ng cch chn sng mang ph fsccho php t kh -c tp m don gy ra.

Phi chn FM ting sao cho n giao thoa vi fsc khng to nnnhiu trn mn hnh.

H NTSC hay xy ra s sai pha trn -ng truyn, gii php cho

vn ny l my thu c nt iu chnh pha sa mu ( 2 nt chnh TINThoc HUE) tuy nhin kh nng iu chnh ca 2 nt ny cng c gii hnnn xem sau mt thi gian my NTSC cn -c hiu chnh nh k th khnng hiu chnh mi chnh xc t cht l-ng cao.

2. H truyn hnh mu SECAM (SECAM tun t v mu)H mu theo tiu chun OIRT (t chc pht thanh truyn hnh quc

t)H mu SECAM tri qua nhiu ph-ng php ci tin nng cao

cht l-ng truyn hnh mu c tn nh- sau: SECAM II, SECAM III,SECAM IIIB, SECAM IV, SECAM IIIB optimal. Trong SECAM IIIBoptimal l h mu hon chnh nht v tr thnh h truyn hnh SECAMchnh thc.

a. c im h SECAM III optimal* Tn hiu chi Y -c tnh theoY = 0,3 R + 0,59 G + 0,11 BVi rng di tn l 6 MHz

2 tn hiu "hiu mu" -c truyn i theo tng dng sang pha thu,tn hiu -c biu th bi: DR= 1,9 (R Y)

DB= 1,5 (B Y)

Vi rng di tn c 2 tn hiu "hiu mu" u bng 1,5MHz, chn1,9 tn hiu DRnhm gii quyt tnh kt hp ca h truyn hnh mu vi htruyn hnh en trng.

2 tn hiu "hiu mu" -c iu tn s sng mang mu ph fCRvfCB. Hai tn s sng mang ny -c chn sao cho tnh chng nhiu catruyn hnh -c nng cao.

Tn s sng mang mu ph: i vi cc dng truyn tn hiu DRth tn s khi ch-a mang mu ph khi ch-a iu ch bng fCB =4,40625MHz i vi cc dng truyn tn hiu DB th tn s sng mang mu

ph khi ch-a iu ch bng fCB= 4,25 MHzTn hiu ng bng b theo xung dng: xung ng b mu theo dng -c sp xp

s-n sau xung xa dng, c tn s l fCRi vi -ng truyn DRv fCBvi -ng truyn DB.

ng b theo mnh: trong h SECAM mi hnh nh -c chia thnhMnh l (hay mnh 1) bao gm cc dng 1, 2, 3, 4 n dng 313 v

mnh chn (hay mnh 2) gm cc dng t 314 625.Tn hiu ng b mu theo mnh t :


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+ Mnh 1: t dng 715 gm 9 xung (5 xung d-ng nhn dng tnhiu DRv 4 xung m nhn dng tn hiu DB)

+ Mnh 2: t dng th 320 328 cng gm c 9 xung chia lm 2loi nh- mnh 1.

Ph ca tn hiu mu tng hp

Ph ca tn hiu SECAM gm chi Y v sc C. Sc C gm 2 tnhiu DRiu tn vo sng mang fCRthnh tn hiu iu tn fDBhai tn hiusc fDBv fDR-c hn ch bin thp hn so vi chi Y (trung bnhkhong 30% bin tn hiu chi Y).

b. S m ha h mu SECAM* S

S m ha h mu SECAM

Nguyn l hot ng-a 3 tn hiu mu c bn vo mch ma trn cng ti y to ra E Y,

ER EY, EB EY. Tn hiu chi EYqua dy gi chm ch tn hiu muiu tn cho khi lch pha. Mun truyn ln l-t th o mch S.

Phi ng theo nhp fH/2ngha l c mt dng n ng ln ER EYthdng tip n li ng xung EB EY. Mch iu tn EM tn s sng mangmu ph fsc= 4,43 MHz thc hin iu tn bi 1 trong 2 tn hiu mu cho

0 1 2 3 4 5 6

MHz

FERYBin

FDB

Matrn

Gi chm 0,7mEYEREG

EBi utnFM

Matrn

Sng

mangmu ng bmu nhndng mt

Tn hiuh

SECAMER

EB

CMT

theodng

fmp


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tng dng truy n. Tn hiu i u t n k hiu l fmRv fmB-c nhp chungvi tn hiu chi mch cng c tn hiu SECAM COLOR VIDEO. Haitn hiu mu fmR v fmB c mc 25% so vi mc 100% ca tn hiu chithay nhau xc nh ln cn fsc= 4,43 MHz. Tn hiu FM sound tn s6,5 MHz.

C. S gii m h mu SECAM


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Nhim v cc khi Tch sng ng b tch ly cc tn hiu fmR, EY, fmB, xung nhn

dng trung tn ting. Mch gii nhn: gim bin tn hiu tn s cao lm cho c tnh

ca n ging nh- ban u. Nguyn l hot ng

+ Tn hiu chi -c -a qua dy tr 0,7 ms ri -c khuch i -aton di tn EYvo 3 catt ca n hnh. ng thi nhnh khc ca tn hiuvideo -c -a qua b lc chung chn lc khi phc li tn hiu musau ly ra trung tn mu.

+ Mt -ng trung tn mu -a thng n chuyn mch SW mt-ng -a n sau khi qua dy tr tn hiu (fmR, fmB) sau -a qua mchhn ch bin ri -c tch sng (FM, DET) ri qua mch dii nhn n

ma trn to ra tn hiu G Y, v c 2 tn hiu R Y v B Y. Cui cng3 tn hiu ny -c khuch i cng sut -a vo 3 l-i ca n hnhmu.

c im ca h mu SECAM Truyn ln l-t 2 tn hiu theo tng dng (nn cn c chuyn mch Dng iu tn 2 tn hiu mu bng 2 sng mang ph fOR= 4,40625

MHz

fOB= 4,25 MHz vi khong cha tin mu 4,02 4,68 MHz Tn hiu color video gm 8 tin tc

+ 4 tin tc nh- ca en trng+ 2 tin tc mu DRv DB+ Tin tc nhn dng dc+ Tin tc le mu CHai tn hiu sau ch s dng 1 nhn dng my thu Tn hiu mu iu tn fmEv fmB mc thp hn nhiu so vi tn

hiu chi

2 bin ca di tn fmBv fmR(3,9 4,2 MHz v 4,68 4,75 MHz)l ph ca tn hiu nhn dng gc.

3. H mu PAL

PAL (phase alter nativeline thay i theo dng pha). H PAL ra i Ty c theo tiu chun FFC y ban thng tin lin bang.

EY= 0,3 ER+ 0,59 EG+ 0,11 EBU = 0,493 (EB EY)V = 0,877 (ER EY)+ Trong mi mt sng tn hiu gm c tn hiu chi v 2 tin tc

mu -c m ha. Mi mt tin tc mu thc hin iu ch sng mangmu ph theo ph-ng php iu bin nn, ph-ng php iu ch sng mang

ph iu ch 900c mt tin tc mu s thc hin o pha ln l-t theo

dng V=0,877 (ER EY) nhm mc ch chng sai pha trn -ng truyn


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khi thc hin i u ch tin tc mu ng-i ta l ng vo tn hiu chi pht ing b mu cng -c chn mt s pha.

Gc 0 ca tn hiu sng mang mu ph lm c s sau -c o

pha i 1350v chn vo xung ng b dng pht i.

Ph ca tn hiu ng b dng n v n + 1

Ph ca tn hiu mu tng hpPh ca tn hiu mu tng hp gm tn hiu chi c di tn

(05MHz), tn hiu sc C gm hai tn hiu u v mt phn di bin tn trnb. S m ha h PAL* S

1350v Cn+1

B YU

Cnv ng bdng (n)

1350

ng bdng (n+1) 1250

Matrn

Daongsngmang

Dy tr 0,7ms

SAMI

SAMII

opha900

o pha+1350

Bcng

I

Bcng

II

Bcng

C ngmu

0

fH900

YER

EG

EB

Ura

EB

EY

opha900

o pha1350

1 2 3 4


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Nhim v cc khi Ma trn: bin i 3 tn hiu thnh ERYV, EBY=U iu ch SAM I. II. iu ch tn hiu mu vi dao ng sng mangD-i hnh thc iu bin nn Dao ng sng mang mu: to in p c bin khng if=3,58MHz

Dy tr 0,7 ms gi chm tn hiu chi EY B cng I, II, III: cng tuyn tnh cc tn hiu o pha: o pha dao ng sng mang mu Cng mu: iu kin cho xung ng b mu i qua n b cng III.

H PAL vn s dng iu bin nn vung gc nh-ng vi s thay iv pha ca sng mang mu ph:

Pha 00dng iu bin nn cho tn hiu mu th nht (khc vi330nh- h NTSC)

Pha +900v 900iu bin nn ln l-t tng dng cho tn hiu muth 2 (khc vi NTSC dng 330+ 900= 1250cho tn hiu mu th 2.

Pha le mu l +1350hay 1350ln l-t cho tng dng ang truync pha l +900hay 900. Nh- vy mt mu m c ta mu

V = 0,877 (ER EY). U = 0,443 (EB EY) tc l m (U, V) th U ginguyn iu bin sng mang ph f

sccn V iu bin sng mang ph c

pha +900hoc 900theo tng dng ln l-t ngha l mt dng vn truyn ic 2 tn hiu U v V, nh-ng mt dng V mang u d-ng, dng kia Vmang u m. C th coi PAL truyn mt mu tht l m (U, +V), mt mugi l m (U, V) nh cch truyn ny my thu c th t ng iu chnh-c s lch pha. Khc phc -c nh-c im ca NTSC.

H PAL c cc ch tiu bin nh- NTSC -c gi trong knh CCIRch khc v pha le mu.

T iu chnh sai pha my thu gi s ta truyn i dng th NTSCmu m' (U, V) dng n+1 gi mu m' (U, V)

v'v

v'

v

m'

m"

u1

m'1m'

u0


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Nhim v cc khi Tch sng ng b: tch ly tn hiu video audio v xung ng b

mu Khuch i tn hiu mu: khuch i v nng cao bin tn hiu o pha 1800: o pha tn hiu mu 1800.


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Dao ng thch anh: ph t ra tn hiu c t n s 4,43 MHz, bin

khng i v fa = 1350. Cn cc khi khc ging nh- cc h khc (NTSC v SECAM)

Nguyn l hot ng

Tn hiu chi qua mch gi chm 0,7ms ch tn hiu mu mchma trn. Tn hiu mu iu bin nn vung gc -c tch ra nh mchkhuch i trung tn mu, y n chia thnh 3 -ng.

+ Mt -ng o pha 1800n mch cng I

+ -ng th 2 qua dy tr 64 ms n mch cng I v mch cng II+ -ng th 3 i vo mch cng IITn hiu -c cng vi nhau. Dng th n c u, v qua mch o n

im a l u, v cn im b ch-a xc lp (n nh dng tr-c n 1) im c lu, v n dng th n + 1 truyn mu gi u, v, n im a l u, v im b nh

dng tr-c u, ra mch cng 1 v 2v; im c l U, V, cng ra mch cng 2l 2u... cng ra 1 (a + b) lc th c +2v, lc th 2v cn cng ra (2) (b+c)lun l 2u. Hai mch tch sng iu bin nn vi cc pha ca sng hnh sin4,43 MHz thch hp s cho ra 2 in p mu 2v v 2u -a vo mch matrn cng vi tn hiu chi ti lp cc tin tc mu.

c im h mu PAL Tn hiu trong h mu PAL cha ng 7 thnh phn tin tc (ting,

chi, ng b dng, ng b mnh, 2 tin tc m, tn hiu ng b mu pht

ra t 1350.

+ Trong mi mt dng tin tc c 2 thnh phn mu nh- vy tin tcmu pht ng thi.+ Sau mi mt dng th 1 thnh phn tn hiu mu -c o pha

hn ch chng sai pha trn -ng truyn, nh- vy tn hiu mu -c phtng thi v ln l-t.

+ Sng mang mu ph -c chn l 4,43 MHz bng tn s mangmu ph h NTSC chng nhiu.

+ Tn hiu ting cng -c chn thc hin chng nhiu+ Tin tc mu thc hin iu bin nn trn sng mang mu ph xoay

pha vung gc vi nhau.

* u im H PAL c mo pha nh hn hn so vi h NTSC H PAL khng c hin t-ng xuyn ln mu H PAL thun tin cho vic ghi bng hnh (VTR v VRC) hn h

NTSC* Nh-c im

My thu hnh h PAL phc tp hn v cn c dy tr 64ms v yu cudy tr ny c cht l-ng cao v tnh kt hp vi h truyn hnh en trngkm hn so vi h NTSC

4. So snh gia cc h (NTSC PAL SECAM)a. S ging nhau


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C 3 h mu u gi ng nhau v nguyn l lm vic v c k t c umch in, chng thc hin -c vic kt hp gia truyn hnh en trng vtruyn hnh mu.

b. S khc nhau Tn hiu mu NTSC truyn i -ng b mo pha -c khc phc

bng 2 nm colour v HUE. Tn hiu PAL v SECAM khc phc -cnh-c im trn.

Ph-ng php m ha h NTSC v PAL l dng ph-ng php iubin n vung gc, cn SECAM dng ph-ng php iu tn

Cc mch gii m, m ha khc nhau* Cc thng s k thut

NTSC PAL SECAMTn s qutmnh

60Hz 50Hz 50Hz

Tn s qut dng 15750 Hz 15625 Hz 15625 HzDi thng tn 5 6 MHz 7 8MHz 7 8 MHzTrung tn ting 4,5 MHz (M, Nht) 5,5MHz

(PALBG)6MHz (PAL I)6,5 MHz (PAL)

6,5 MHz

u im: H PAL mo pha nh hn hn so vi h NTSC H PAL khng c hin t-ng xuyn ln mu H PAL thun tin cho vic ghi bng hnh (VTR v VCR) hn h

NTSCNh-c im:

My thu hnh mu h PAL phc tp hn v cn c dy tr 64ms vyu cu dy tr ny c cht l-ng cao v tnh kt hp vi h truyn hnhen trng km hn so vi h NTSC.

IV. Nguyn l thu pht hnhTt c cc nguyn l truyn hnh en trng u -c tn dng

truyn hnh mu. Ni khc i truyn hnh mu tr-c ht phi lm li ht cccng vic c ca truyn hnh en trng. im khc bit gia truyn hnhen trng v truyn hnh mu l ch: Thay v ch quan tm ti tnh chtmu sc ca tng im trn nh. my pht s dng b m ha mu mha cc mu ti to li cc mu nguyn thy m pha pht gi sang.

1. Nguyn l truyn phta. S


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S khi bn phtb. Nguyn lnh a mu cn truyn i -c qua thu knh quang hc hi t

nh sng, sau thu knh -c quang thng f, -c -a qua lng knh khc x ly cc tn hiu mu c bn cc tn hiu ny li -a qua a lcmu, a lc mu l nhng b lc nh sng c di tn rt hp ch chomt mu nht nh. Sau a lc mu ta -c 3 mu c bn R, G, B theotng h-ng ring bit v tc ng ln ba n quang in bin i tn hiu

nh sng thnh tn hiu in, u ra cc n quang in -c cc in pER, EB, EG. Cc tn hiu ny khng -c gi trc tip ti my thu m -c-a qua ma trn bin i. Ma trn c th l ma trn mch IC hoc b intr. Sau ma trn bin i ta -c tn hiu chi EYc tr-ng cho nh entrng v hai tn hiu s mu EREY, EBEY, hai tn hiu mu ny li -c-a ti b m ha iu ch sng mang t hp thnh tn hiu mu ny-c -a ti b m ha iu ch sng mang t hp thnh tn hiu muC. Tn hiu mu C -c lng trong ph tn ca tn hiu chi EY, ri tt ccc bin vo my pht sng mang hnh FAtn hiu m thanh cn truyni -c iu tn vi sng mang c tn s l F t sau cng phi hp visng FA -a ra anten pht sng, to thnh sng in t tr-ng lan truyntrong khng gian.

Vi cc h khc nhau th Fts khc nhau:H NTSC (M, Nht) : Ft= FA + 4,5 MHzH PAL BG (Ty u): Ft= FA+ 5,5 MHzH PAL I (Hng Kng): Ft= FA+ 6,0 MHzH PL D.K (Trung Quc, Vit Nam): Ft= FA+ 6,5MHzH SECAM HIB (Nga): Ft= FA+ 4,5 MHz2. Nguyn l thu (ti ti li hnh mu)

a. S


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b. Nhim v cc kh i Phn cao tn trung tn tch sng+ Hp knh: Chn lc v thu tn hiu trong khng gian vi cc di

tn t-ng ng l:UHF: (30 3000) MHz t-ng ng l= (0,1 1)m

VHF: (30 300) MHz t-ng ng l= (1 10)mTn hiu thu -c -a ti khuch i v i tn hiu xung thnh tn

hiu trung tn vi:Trung tn hnh: FA= 38 MHzTrung tn ting: Ft= 31,5 MHz+ B my khuch i trung tn: Khuch i in p trung tn ln ln

theo cu ca my.+ Mch tch sng video: tch ly tn hiu hnh -a v khi -ng

hnh.

+ Mch AGC: l mch t ng iu chnh h s khuch i+ Mch AFC: mch t ng iu chnh tn s ngoi sai: -ng ting:+ Mch khuch i cng h-ng nhm khuch i tn hiu m tn sau

tch sng v kch thch cho tng cng sut m tn lm vic.+ Mch khuch i cng sut m tn: Khuch i v phi hp tr

khng -a tn hiu m thanh pht ra loa. -ng hnhKnh chi:+ Dy tr: Dng lm tn hiu in p chi EY+ Mch khuch i E

Y: Dng khuch i in p chi cho ln

Knh mu:+ Mch gii m mu: Dng gii m ly ra hai tn hiu mu

ER EY, EB EY.+ Ma trn GY: To li tn hiu mu th 3 EG EYm i pht khng

gi i t hai tn hiu mu ER EY, EB EY.+ Mch ma trn R, G, B: khi phc li 3 tn hiu mu c bn E R, EA,

EBt ba tn hiu mu (ER EY), (EB EY) vi tn hiu chi EY.+ Mch khuch i ERdng khuch i tn hiu in p mu lc

v cc tnh -a ti Catot KGca n hnh+ Mch iu chnh cn bng trng: Dng iu chnh cho ba tia

in t bn ln cc im pht ra mu t-ng ng trn mn hnh vi mtc-ng thch hp sao cho khi ch-a c tn hiu mu -a n th vic phatrn nh trn mn hnh s ra en trng.

+ Mch tch xung ng b: lm nhim v khuch i v phn chiaxung ng b.

+ Mch khuch i cng sut mnh: y l s to ra xung rng c-aqut mnh vi tn s fV= 50Hz vi h PAL, SECAM v fV= 60Hz vi hNTSC -a xung qut mnh ln cun li tia to ra tr-ng li tia in t quttheo chiu dc ca mn hnh.

Phn dng:


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+ Mch so pha: dng so snh gia pha c a xung dng do my tora vi pha ca i pht gi ti t iu chnh li nhp dao ng cho ngb vi pha pht.

+ Mch khuch i m v kch dng: dng khuch i v kchcho tng cng sut qut dng lm vic.

+ Mch khuch i cng sut qut dng: Mch ny c nhim v nh-mt kha ng m theo nhp tn s to ra xung rng c-a qut dng tora t tr-ng li tia in t qut theo chiu ngang ca mn hnh.

+ Bin p cao p: to ra nhiu mc in p khc nhau cung cpcho my.

Khi vi x l:L ni nhn v pht lnh iu khin cc hot ngca my theo mt c cu ng b. ng thi, khi ny cn nh cc chcnng, cc trng thi -c iu chnh v nh vo . Ngoi ra cn thchin qu trnh chuyn i t tn hiu s sang tn hiu t-ng ng v ng-cli iu khin hot ng my.

Khi ngun: i in p xoay chiu AC 110V v 220V thnh nhiumc in p mt chiu n nh, cung cp cho my lm vic Mch kh t d-: to ra xung t tr-ng rt ngn mi ln khi ta m

my qut sch t d- ng khu vc n hnh, lm cho nh h-ng blong mu.

Khi AV: Lm nhim v chuyn mch khi ta th ch-ng trnh tivihoc cc tn hiu t bn ngoi thng qua cc u thu hoc u pht.

* Nguyn l thu:Tn hiu sng thu cao tn t anten ti hp knh. Ti hp knh n

-c trn tn s mang hnh v ting vi dao ng ngoi sai to ra tn s

trung tn hnh, ting. Sau -c khuch i tn hiu trung tn hnh, ting nng cao bin v tng tnh chn lc tn s. mch trung tn tingchn lc tn hiu m tn, tn hiu pht sng v khuch i cng sut -a raloa, -ng khc -a ti mch lc mu chn lc ly tn hiu mu -a nmch gii m mu ly ra tn hiu mu -a n mch ma trn G Y to litn hiu mu th 3 l EG EY, EB EY. Sau c 3 tn hiu chi EYly ra 3tn hiu mu ER EY, EB EY. Sau c 3 tn hiu mu ER EY, EB EY-c-a ti ma trn RGB cng vi tn hiu chi EYly ra 3 tn hiu mu c bnl ER, EG, EB n mch khuch i cho in p ra ln ln v o thnhcc tnh m ri -a n Katot n hnh, n hnh bin i tn hiu in,

thnh tn hiu hnh nh to ra tn hiu cho mch qut dng, mnh ta lyxung ng b dng, mnh t my pht n mch ng b. Ti y to rahai in p qut dng tn hiu l in p rng c-a v -c -a ti cun litia qut dng v qut mnh c n hnh l cho mn nh sng hon ton vtn hiu hnh nh -c to li nh- ban u do ta quan st -c hnh nhtrn mn hnh.

Ch-ng IIS khi my thu hnh mu

I. S khi:


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Hnh 4.1. S khi my thu hnh muTT Mch t ng iu chnh tn s dao ng ti ch

TK T ng iu chnh khuch i; K Khuch iII. Chc nng cc khi1. Khi chn knh:Tn hiu cao tn ca bng sng VHF v UHF -c -a ti khi chn

knh t-ng ng. Khi chn knh c nhim v chn knh khu, khuch iv bin i tn s thu thnh tn s trung tn: trung tn ting ftttv trung tnhnh ftth(trung tn mang thng tin tn hiu tng hp my (EM).

* Yu cu k thut ca khi chn knh Nhiu ni b ca khi chn knh phi nh, c bit l phi hn chnhiu ca dng khuch i cao tn bng cch chn Tranzito v ch lmvic ca Tranzito lm vic.

Tn s dao ng ngoi sai phi tht n nh. n nh tn sngoi sai ta dng mch AFT (t ng tinh chnh tn s).

2. n hnh mu (CRT)L phn t chnh ca my thu hnh mu n c chc nng l bin i

cc tn hiu mu c bn thnh hnh nh mu (bin i tn hiu in chathng tin mu ca nh thnh hnh nh mu v hin th ln mn hnh)

Ngoi cc in cc n cn cho php thay i -c sng, ti, hit bng cch thay i in p trn cc in cc, iu khin tia in t lch


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ng v lch ngang nh nng l-ng t tr-ng trn qun dy qut mnh vqut dng.

3. Khi -ng tingTn s trung tn th 2 qua b khuch i trung tn -ng ting FIS

(Sound Intermeidium Frequency), tch sng FM, khuch i m tn v -a

ra loa.4. Knh chiThc cht knh chi l cc tng khuch i hnh trong my thu hnh

en trng. N m nhn cc chc nng sau: Khuch i tn hiu chi EYn gi tr cn thit Lm tr tn hiu chi EYmt thi gian cn thit, m bo cho tn

hiu chi v cc tn hiu mu ng vi 1 phn t nh cng n ni vo mchma trn mt lc, nhm cho nh en trng v nh mu trng kht.

Nn tn hiu tn s tn hiu v sng mang mu lc thu ch-ng trnh

truyn hnh mu.5. Knh muL mt khi quan trng ca my thu hnh mu n c nhim v l: Tch ly tn hiu mu ECt tn hiu truyn hnh mu y Khuch i tn hiu mu n gi tr cn thit. Gii m tn hiu mu nhn -c cc tn hiu hiu mu6. Khi ng b mu:C nhim v Tch ly tn hiu ng b mu thc hin ng b, ng pha

c-ng bc mch to sng mang ph trong my thu hnh h NTSC v PAL,thc hin ng pha CMT trong my thu hnh h SECAM IIIB v PAL.

T ng tt knh mu khi thu ch-ng trnh truyn hnh en trnghoc lc thu ch-ng trnh truyn hnh khc h mu hoc mc tn hiu uvo my thu hnh mu qu yu.

7. Mch ma trn:Thc hin 2 nhim v T cc tn hiu hiu mu ERYv EBYto thnh tn hiu hiu mu

th 3 EGYtheo biu thc:EGY= 0,59 ERY 0,19 EBY

T tn hiu EYv cc tn hiu hiu mu to ra cc tn hiu mu cbn:

ER= ERY+ EY

EG= EGY+ EYEB= EBY+ EY

Mch in thc hin cc php ton ny gi l ma trn R, ma trn Gv ma trn B.

8. Cc tng khuch i VideoMc sau mch ma trn dng khuch i tn hiu mu c bn hoc

tn hiu mu n gi tr ln nhm m bo cho n hnh mu hot ngbnh th-ng. H s khuch i khon t 30 40 dB v gi tr in p rakhong 60 n 200V (ty thuc loi n hnh s dng trong my).

9. Khi qut dngC nhim v to ra t tr-ng li tia in t theo chiu ngang.


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Ngoi ra, n cn c nhim v cung c p in p c t n s dng chomch to dng in hi t (ng quy), in p dng in trong mch samo gi v cung cp in p tht n nh cho n hnh.

10. Khi qut mnhC nhim v to ra t tr-ng li tia in t theo chiu ng. Ngoi

ra, cn c nhim v cung cp in p c tn s mnh cho mch to dngin hi t v cho mch sa mo gi.

11. Mch to dng in hi tNhim v l to dng in c tn s dng v dng in c tn s

mnh vi hnh dng v bin cn thit cung cp cho cc c cu hi t-c t trn c n hnh

12. Mch cn bng trng:m bo cho ton b mn hnh khi khng thu ch-ng trnh truyn

hnh hoc khi thu ch-ng trnh truyn hnh en trng khng b nhum mu,

ngha l m bo mn hnh c mu trng nh- my thu en trng.13. Mch t kh tCh hot ng tr-c mi ln thu, -c b tr khi ngun, c nhim

v kh t tr-ng d- trn mn chn, mn che t, ai gi n hnh... do ttr-ng bn ngoi nht l t tr-ng tri t gy ln.

14. Lm sch muDng 2 nam chm hnh xuyn dt. Trong my thu hnh mu,

chnh tm dng bin php thay i gi tr v chiu dng in 1 chiu chyqua cun li tia dng v mnh.

15. Khi iu hnh

Gm cc chit p hoc phm n... tt m my, chn ch-ng trnh,iu chnh t-ng phn, sng, bo ha mu, sc mu, m l-ng, msc...

16. Khi ngun cung cpNhng yu cu v ngun cung cp cho my thu hnh mu in p 1 cung cp cho Tranzito v IC phi c n nh cao,

gn sng phi nh. Khi c s c t bin trong my thu hnh th nguncung cp phi -c ct ri khi mch in.

Phi c mch bo v khi c hin t-ng qu p v qu ti.

Ch-ng IIIMch ngun trong my thu hnh

A. Gii thiu v cc loi ngun trong my thu hnh1. c imMy thu hnh l tng hp cc ch-ng trnh mch in nh- khi

ngun, cng sut mnh, m thanh... cc khi ny u gp phn quan trngvic ti to li hnh nh t ni pht gi n.

Khi ngun l b phn quan trng cung cp ton b nng l-ng choton my n to ra cc mc in p khc nhau cung cp cho cc khi

khc nhau. Do phn ln h- hng u do phn ngun, my thu hnhhot ng tt n nh th cc ngun to ra phi m bo n nh v bng


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ph ng cao. Ph n ngu n trong my thu hnh mu hin nay -c s dng r ta dng p ng yu cu ca tng loi my.

II. S khi ngun

1. Chc nng cc khia. Bo v chng nhiuBo v thit b v mng in cng nghip hn ch nhng nhiu xut

hin trn -ng dy -a vo trong my thu hnh v nhiu t my.b. Kh tMch kh t to ra t tr-ng mnh khi bt my t ha cc t d-

trn mn hnh cho ng u sau t tr-ng xung rt nh chng nhh-ng ca t tr-ng tri t nh h-ng n my.

c. Bin pC nhim v bin i in p cng nghip thnh in p thch hp

cung cp cho my theo yu cu ca my to ra in p khc nhaud. Khi chnh l-uC nhim v bin i in p xoay chiu sau th cp thnh in p

mt chiu, b chnh l-u th-ng dng diot thay ie. Thit b phN l cc mch iu khin hay mch nhn i in p cng c th l

cc mch lc bo v hay l b to dao ng.f. Mch lcDng t ha c in dung ln phi hp cc cun cm c gi tr ln

mc thnh mch lc phn chia -ng i cho cc thnh phn xoay chiu sau

chnh l-u nhm san bng gn sng gi cc thit b in t trong mchg. Khi n pC nhim v n nh dng in mt chiu, duy tr cho in p

mt chiu ra trn ti lun n nh mc d mc ngun in u vo lunthay i hoc dng chy ra ti lun thay i.

h. Khi bo vm bo an ton cho thit b cng nh- cho bn thn mch in, nu

c s c chp mch lm dng in tiu th tng ln th n s kha ngay ch ngun li. Mt s mch b nh- mch chng qu p, qu dng chp ti.

III. Mt s ngun in th-ng s dng

1. Mch n p tuyn tnha. c im

Bo vchngnhiu

B/ANgun

Ch nhl-

Mchlc n

pTi

ACin

Kh t Thitb ph Bo v


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Ngu n trong my thu th-ng s dng l ngu n B 110 DC vi nnh cao, gn sng nh t -c iu ny cc my c tr-c y s dngn p thay cho cun lc.

Mch ngun n p tuyn tnh v mch ngun s dng phn t n pchnh l transitor n p gi l "S Regu". Dng in p cho khi chc nng

trn my -c i qua transitor ny mt cch lin tc, transitor n p ngvai tr nh- mt in tr hiu chnh in p cp cho ti theo chiu h-ng nnh in p ng ra.

Mch ngun n p th-ng -c s dng a phn my ni a M hnh mch ngun n p tuyn tnh -c m t nh- sau:

M hnh mch n p tuyn tnh

Ta c Vin= Vout+ VRegue Khi VRegurtng, VoutgimKhi VRegurgim, Vouttng

Khi in p ng ra tng gi tr "bin tr" tng, st p trn in trtng dn n in p ng ra gim.

Ng-c li khi in p ng ra gim lm cho gi tr "in tr" gim dn

n in st p trn in tr gim Ura tng theo chiu h-ng n nhnh nht.

b. S in p tuyn tnh

ACin

Vin Vout

VRegur

Ti

ra11 V+1kW


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Nhim v cc khi+ Cu nn: lm nhim v nn in p xoay chiu thnh in p mt

chiu ch-a n nh cp cho my.+ Khi lc: lm nhim v san phng gn sng cho dng in u

ra n nh nht.+ n p: trng tm ca mch n p l mt transitor cng sut lnng vai tr mt in tr thay i ni t ngun d-ng ch-a n nh n ngra n nh n ng ra ng n nh. V phi th-ng xuyn chu dng cao nnth-ng ng-i ta mc thm mt tr cng sut ln song song vi transitor np gnh bot cho transitor ny.

+ Khi ly mu: gi cho in p ng ra B lun lun thay i, utin ng-i ta thc hin ly mu gm cc in tr R1, R2, R3ni tip t Bxung mt. Chit p R2iu chnh in p ly mu l 6V chng hn nh-vy khi B thay i th p ly mu cng thay i theo.

+ in p chun: th-ng l ngun p khng i ca mt zenen it.+ Phn d sai: nhn cng lc hai ngun p vo l p mu v pchun, nu p mu ng bng p chun, phn d sai s cho ra sai s mctnh mt chiu no t-ng ng vi mch thit k sn B ra l 110DC.nu B b gn tt xung chng hn p ly mu s tt xung d-i 6V trong p chun vn nh- c, tng d sai s bit ny v cho ra p sa sai cao hnmc tnh. T-ng t nh- th p sai thp hn mc tnh nu B b tng cao.

+ Kt thc: thc cht l mt tng khuch i m ra nhiu hay t typ sai s -a v.

Cc B cao hay thp sao cho B lun lun mt v tr no nh-

thit k.+ Khi bo v: c nhim v bo v mch trnh khi b chp mch

hay tng in p trong my bo m an ton cho bn thn ng-i s dng.


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S tiu biu cho mch n p tuyn tnhNhim v cc linh kin R1, R2cp dng cho cc B/Q1v cc C/Q3 Q2phn t n p

Q1phn t thc tng li bv dng ca mch n p

Q3phn t d sai. Dz to in p chun cho cc E/Q3 R4hn ch dng Ic/Q3 R5cp dng phn cc cho it zever (Dz) R6, R7, R8hnh thnh cu phn p cp cho cc B/Q3(ty ly mu) R3l tr r dng cho phn t n pNguyn l hot ng: ta c: Vin= Vout+ VCE/Q2(*)Khi in p (Vout) lm cho VB/Q3tng dn n lm cho Q3dn mnh

dn n in p cc C/Q3gim xung khi in p cc Q3gim th cc BQ1,

Q2gim dn n n yu st p trn mi ni CEQ

2tng, nh- vy lm

cho Vragim (n nh).Ng-c li: khi in p ra gim dn n in p cc BQ3gim lm

cho Q3gim in p cc CQ3tng ln lm Q1, Q2dn mnh st ptrn mi ni C EQ2gim nh- vy Vratng.

2. Ngun n p ngt ma. c im Ngun n p ngt m cn c tn gi l ngun switching -c trang

b cho mt s my ni a v my a h i mi, do hot ng ch ngt m nn hiu sut ca mch cao hn so vi loi n p tuyn tnh, kch

th-c tm gii nhit nh hn tm n p rng hn.


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a s trong cc my ti vi mu a h ng-i ta th-ng thi t k mchngun hot ng vi gii in p t 80V n 240V AC vic chuyn i ny-c thc hin mt cch t ng.

Hot ng ca mch n p ngt m s dng trong ti vi mu hinnay -c thc hin theo cch sau:

+ Gi nguyn tn s, thay i rng xung+ Thay i tn s, gi nguyn rng xung+ Va thay i tn s va thay i rng xungb. Nhng nh h-ng xung n in p mt chiu cp cho ti

S thay i tn s, rng xung n in p mt chiuTa bit rng trong mch lc thng thp in p ra t l nghch vi thi

gian ca mch v t l thun vi tch phn ca in p vo theo thi gian.V0= 1/t fU1dtNu ta xt trong mch trong mt chu k ca tn hiu: V0= 1/t fU1dt

Hay ni cch khc i: in p ng ra t l thun vi gi tr trung bnhca in p vo trong mt chu k.

Trung bnh ca Vi1> Vi2do phn din tch gch cho ca Vi1> Vi2Gi tr tch phn ca Vi trong mt chu k chnh l din tch phn gch

cho. Nh- vy gi tr trung bnh ca mt tn hiu s t l thun vi din tchm tn hiu chim th d: Vimax

C. Cc ph-ng php to xung ngt mn p ngt m hot ng theo kiu thay i rng xung t khi s

dng hn 2 ph-ng php cn li. Hin nay thc hin ph-ng php nyng-i ta th-ng s dng OP AMP (mch khuch i thut ton) y lmch khuch i c mt ng vo cng + v mt ng vo m hot ng theokiu so snh.

TON

TON

IT

Vi2

Vi1

VDC1

VDC2

Vi1

Vi2

TON

V+

V

+

V0


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Khi V+ > V V0= + VccV+ < V Vcc

Bng cch -a xung rng c-a chun vo V + in p DC cn n nhvo chn V, bng cch thay i VDCta c th nhn dng xung c rng

thay i ng ra

Gi nguyn rng xung thay i tn s ngt mPh-ng php ny -c s dng kh ph bin trong thc t. thc

hin ng-i ta th-ng s dng mch dao ng a h dao ng Bloking tuynhin trong tivi mu mch dao ng Blocking -c thc hin nhiu hn c

+ Mch dao ng a hi

Mch dao ng a hi cn bn

1uF 1uF


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Chu k dao ng T = 0,7 (C2Rb2+ C1Rb1) nh- vy thay i t n sdao ng ta thay i gi tr Rb1hoc Rb2, gi tr Rb1, Rb2chnh l dnin ca transitor.

+ Thay i tn s dao ng Bloking: mch dao ng Bloking hay cngi l mch dao ng nght -c s dng kh ph bin trong tivi mu. y

l thnh phn in rt quan trng.B. Khi ngun trong my DAEWOO1. S


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s

kh

i

C

fH


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2. Tc dng linl kin P801 : sc cm ngun . SW801: cng tc ngun LF 801: (TLFL03B) cun lc nhiu cng nghip R809 v P802: kh t d-

D801D804 cng vi C806 C809 hnh thnh cu lc in mtchiu Bo t in p xoay chiu cp cho mch

R801 : bo v qu dng C825 : t lc ngun Bo Bin p T802 : bin p ngun xung dn ngun cho I801 Cun AB : l cun s cp Cun CDE : l cun hi tip.duy tr dao ng Cun IF : l cun th cp ly ra ngun 20V nh vic nn lc ca

it D805 v t C823

IC 801 : IC chuyn mch dao ng , ngt m xung+ Chn 1 : ni t+ Chn 2 : nhn cc -ng hi tip+ Chn 3 : nhn ngun Bo t cun s cp ca bin p T802+ Chn 4 : u ra ngun B1 103+ Chn 5 : b trng IC 802 : n p ngun 5V+ Chn 1 : nhn ngun vo+ Chn 2 : ni t+ Chn 3 : u ra 5V

C824 : t lc ngun B1 5 -ng hi tip cp vo chn 2 IC801+ -ng qua R806 cp ngun to thin p cho IC801+ -ng qua C826 R802 duy tr dao ng.+ -ng qua D8 1 0 ly in p B 1 t u ra quay v u vo qua

R804 v D808 vo chn 21C801+ -ng qua D807 v R802 l -ng mt chiu -a vo chn

21C801 duy tr dao ng+ -ng ly xung dng t chn 10 bin p cao.p T402 qua C830

R831 v chn 21C801 quyt nh tn s dao ng ngun bng tn s daong dng T402 bin p cao p

+ Chn 1 : to in p cp cho CQ402+ Chn 2 : nhn in p l03V t ngun B1 ti+ Chn 3 : to in p dao ng a ti vi x l v IC501+ Chn 4 : ni mt xoay chiu+ Chn 5 : to in p cp cho IC401 (78L12 ) to ra in p 12V

cp cho mch+ Chn 6 : to in p ABL+ Chn 7 : cp ngun cho IC cng sut mnh

+ Chn 8 : ni mt+ Chn 9 : to ra in p 108 V cung cp cho cng sut sc


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+ Chn 10 : to in p xoay chiu (6 12V ) cp cho si nung.+ Bin p T402 cn to ra in p HV cp cho nt n hnh

to in p mt chiu FOCUS cp cho G3to in p SCREEN cp cho G

Nguyn l hot ng ca mchin p xoay chiu cng nghip t gic cm P801 qua cng tcSW801 qua cun lc nhiu cng nghip vo cu nn lc to ra in p Bocp cho bin p xung T802 v a ti IC801 to ra ngun l03 n nhcp cho mch

Bin p xung T802 :Cun AB cp ngun Bo vo chn 31C801 v ly ra ngun B1= l03V

chn s 41C 801Cun IF ly ra ngun 20V nh vic nn lc ca D805 v C823, qua

R815C825 vo chn 1 IC n p IC802 ly ra ngun 5V cp cho chn 421C

vi x l (IC901) V chn 71C vi x l l ngun RESET Hot ng ca ngun RESETKhi mi cm in chn s 71C vi x l c in p cao l 5V mi

hot ng. Lc c dng ng-c chy D811 lm cho Q802 thng Q803tt, ngun 5V qua tr R817 Cp cho chn 7RESET .Khi ngun 5vb thpd-i 4,3V dn n n p D811 khng c dng ng-c chy qua lm choQ802tt, Q803 thng dn n khng c in p RESET vo chn 71C vi sl nn vi x l khng lm vic

+ Ngun l03V t chn 4IC801 qua gic cm P550 qua 2 in tr hp nh D408 (ZPD9.1) to ngun 9V cp cho dao ng dng mnh (chn40 IC501) Phn tch mch Stanby: khi my dang lm vic th chn 18 IC vix l c in p thp i qua R461 a n chn BQ 421 lm cho n nytt dn n in p cc Q421 dng ln cao lm chn BQ422 c in plm cho n ny thng bo ho cp ngun cho chn 401C501

Khi ch tt ch chn 181C501 c in p cao -a n ccBQ421 thng dn n in p chn C n ny st xung lm cho n Q422tt dn n ct ngun cp cho chn 40IC501.

+Ngun l03V cn cp cho tng kch dng (s Q401) v cng sutdng (s Q402)

+ Ngun l03V -c h p qua Rl03, n p nh D931 to ngun33V cp cho IC903 chuyn di sng+ Ngun 103V qua tr R605 cp cho tng cng sut ting Q602

Q604+ Ngun l03V cp cho chn s 2 ca BA cao p . T y BA cao p

to ra nhiu mc in p cung cp cho my .+ Ngoi ra khi ta bm cng tc ngun SW801 m my, phn lm

vic cho ra in p l03V v 5V ng thi cho ra 1 cng tc ph SUB SW(gn trn cng tc chnh) -c ng li cho chn 1 v chn 2 ni vi nhau,n Q909 thng lm cho n Q910 tt, t C917 phng in. Dng np i t

+5V qua R939, qua C917, qua BEQ909 v mt. Khi b tay khi cng tcngun, cng tc ph b ngt ra (cng tc chnh vn ng) lc ny t C917


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phng in. Dng phng t d-ng t qua R940 qua mt qua + V quaR941 v cc m t. Kt qu cc B n Q909 xut hin in p m l Q909b kho li, in p cc C n ny tng cao lm Q910 thng v cc C Eca Q910 ni vo chn 17 v chn 28 IC901 ln khi Q901 thng lm cho 2chn ny ni vi nhau qua D911 pht lnh cho IC901 m ngun cho my

lm vic . n Q910 ch thng trong thi gian t C917 phng in .Thigian phng in n Q910 li tt. Mi mt ln n Q910 thng ri li ttlm chn ngun.18 IC910 chuyn t trng thi ny sang trng thi kia.Chnh v vy nguyn tc mc mch cao p l dong i qua hai in tr songsong R550 v R551. Khi mch cao p b qu ti, dng qua hai tr ny lnln sinh ra st p trn chng n l cho Q550 thng dn n cc BQ551 cin p cao lm cho Q551 thng dn n chn 1 P551 c in p lm cho

Q910 thng ct ngun v tt my+ it D809: Lm nhim v bo v qu p .

V in p ra l ni tip ca in p vo v l do no m IC801 bchp s lm cho ton b in p vo ln ln trn t C825 qua cun AB cabin p T802 a thng vo mch gy nguy him cho my. Chnh v vyng-i ta c lp 1 it D890 (SR 2M) bo v, it c in p khong160V, khi IC801 b chp hay hng dn n mt ngun an ton cho my

Do kiu mch ngun ny l in p vo ni tip in p ra cxung dng khng ch. in p ngun ra vn m bo, my lm vic bnhth-ng. Chnh v vy trong iu kin ngun ra thp ng-i ta khng cndng bi p ch 110V m my vn lm vic bnh th-ng

+ u im : n gin, gn nh, tnh n nh cao+ Nh-c im: lkhng cch li nn s vo my b git v mch AV

phc tp hn.3. Mt s h- hng v cch khc phcKhi ch tt ch (ngun lm vic, mch cao p cha lm vic,

khng c xung dng -a v) in p ra l03V khng sai khc g so vi myang lm vic bnh th-ng. Ngun 20V khi tt ch l 18V khi my anglm vic c dao ng dng v mch cao p lm vic, m khng c xungdng v th in p ra l03V ch cn 85V, mn hnh sng yu co li, c tingrt ngun. Cc linh kin quyt nh ti mch ngun lm vic bnh th-ng

(khng k n -ng dn xung dng) l C821, C826, D807, D806 songsong vi C831, R802, R806. Khi bit chc IC ngun 801 khng b hngm vn b hng ngun th ta kim cc linh kin ny v tr s v -ng dntrn mch in ca chng. Khi trm my ang lm vic m ngun ra yu, cting rt ta cm thy c xung dng v th ta cn kim tra mch cc linh kinC830, R831, R804, R808 v D810.

Mt s b phn ca my DAEWOO lm vic bnh th-ng th khih ti 103V (rt rc P550 hoc ct -ng dn l03V v cao p). V h ti20V (nhc R821 ra khi mch) in p 103V v 20V vn nh th v nnh.

Khi cho ti gi l mt bng in vo ngun l03V, bng in s sng,ngun sp xung cn 85V c ting rt.


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Trong qu trnh s a cha c nhi u tr-ng hp ta khng xc nh-c cc h- hng ngun hay hng cao p th ta c lp li phn ngun bngcch h hai ti v o c chnh xc nh trn. Nu khng ging nhtrn thchc chn hng phn ngun.

Khi gp tr-ng hp bt cng tc ngun m khng thy n bo

sng kim tra cu ch vn thy ch bnh th-ng .Ta phi o ngay in trit bo v D809. Nu khng chp th c th do 2 nguyn nhn: 1 l doD809 thng chp l d ng Q402 thng chp. Lc ny rt rc P550 ra vdo li nhtrn nu chp l do D809 hng ta tin hnh tho b it ny ra.Nu thy ht chp th do s dng hng v ta tho b Q402 ra li cho kcng v khng nn thay vo ngay. Kim tra li IC801 c th hng chp ura v u vo. Khi thy khng c chuyn g vn bnh th-ng mi thay sngang vo v it n p vo.

Mt s bnh khc cng hay gp l n t C825 (220 400V) bnh nyl do ty h qua em in l-i cao, my h ti in cao lm hng in tny. Th-ng vic hng khng km theo hng cc linh kin khc phnngun. Nh-ng do ho cht trong t bn ra mt s ch lm d mch dn nIC vi x l khng lm vic hoc b hng, gp tr-ng hp ny phi thochasis ra khi my lau tht kh cc vt dung dch hoc em ra bng n-cl hay x phng ri sy kh sau mi thay t v lp chaisis vo my chyth kim tra.

C . KT LUN V PHN NGUNB ngun trong my thu hnh l yu t .rt quan trng n khng th

thiu -c khi ngun l mt b phn cung cp nng l-ng cho ton my

n to ra cc mc in p khc nhau cung cp cho cc khi khc nhau,do trng mch in t b ngun khng hot ng th khng c ngunphn phi n cc mch in gip. cho my hot ng -c,do phnln h hng xy ra phn ngun. my thu hnh hot ng tt v nnh , bng phng phn ngun trong cc my thu hnh hin nay c sdng rt a dng p ng yu cu ca tng my. Nh- vy mch ngunlun phi lm vic vi in p cao, dng in ln do m h hng haytp chung ch yu y.


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K T LU N

Qua thi gian nghin cu, lm n em hiu thm rt nhiu vchuyn ngnh ca mnh. Vi thi gian lm c hn cng vi s gip

h-ng dn nhit tnh ca thy gio, c gio, bn b, em hon thnh -c n ng thi gian quy nh, m bo ni dung yu cu ca n.Sau khi lm xong n em c thm kinh nghim v chuyn ngnh

ca mnh. l mt nhn vin gii c th lm vic -c l ng-i giichuyn mn, l thuyt ln thc hnh vo thc t. Do kin thc v chuynmn ca em cn nhiu hn ch v thi gian cng c hn v s va chm thct cha c kinh nghim nhiu nn trong qu trnh lm n khng thtrnh khi nhng thiu st. Em rt mong nhn -c s ng h v ng gp

kin qu bu em c thm kinh nghim b-c vo i mt cch t tin.Mt ln na chng em xin chn thnh cm n cc thy gio: ThS.

D-ng Thanh Ph-ng, bn b gip em hon thnh -c quyn n nyng thi gian quy nh.

Em xin chn thnh cm n!

SINH VIN

Nguyn Minh Hin


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Mc lc

Li ni uCh-ng I: Nguyn l truyn hnh mu .................................1

I. Nguyn l truyn hnh mu...................................................................1II. Tn hiu trong truyn hnh mu .......................................................3III. c im ca h truyn hnh mu...................................................6IV. Nguyn l thu pht hnh.....................................................................23

Ch-ng II: S khi my thu hnh mu ..........................28I. S khi: .......................................................................................................28II. Chc nng cc khi .................................................................................29

Ch-ng III: Mch ngun trong my thu hnh ...............31A. Gii thiu v cc loi ngun trong my thu hnh .............31

II. S khi ngun .......................................................................................32III. Mt s ngun in th-ng s dng .............................................33B. Khi ngun trong my DAEWOO .......................................................38C . KT LUN V PHN NGUN .......................................................................44

KT LUN................................................................................................45

Truyen Hinh Mau

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