PHN 1: GII THIU V U THU V TINH 1. Gii thiu chung Khi truyn hnh v tinh u tin c tung ra th trng vo u nhng nm 1990, cc ng ten cho ti nh l kim loi t tin v chim mt khng gian rng. Trong nhng nm u, ngi xem phi tr mt ci gi rt t vi khon chi ph u t khng nh c th lp t anten cho ti nh. Truyn hnh v tinh l gp phi kh khn trong vic qung b v truyn hnh cp. Hm nay, bn s thy cc anten cho v tinh nh gn ngi trn nc nh khp Hoa K. Li xe qua cc khu vc nng thn vt ra ngoi vng ph sng ca cc cng ty truyn hnh cp th bn s tm thy cc anten cho trn hu ht cc ngi nh. Cc Cng ty truyn hnh v tinh ln ang thu ht thm nhiu ngi s dng hn na vi cc b phim mi ngy, s kin th thao v tin tc t khp ni trn th gii v l s ha hn ca b phim v cht lng hnh nh v m thanh. Truyn hnh v tinh cung cp nhiu gii php cho vn qung b v truyn hnh cp. Mc d cng ngh truyn hnh v tinh vn ang pht trin, n tr thnh mt s la chn ph bin cho nhiu ngi xem truyn hnh. 2. Vn chng trnh qung b Khi nim, truyn hnh v tinh l mt loi truyn hnh qung b. l mt h thng khng dy cung cp chng trnh truyn hnh trc tip n ngi xem ti nh. C hai chng trnh truyn hnh qung b v truyn hnh v tinh u truyn cc chng trnh thng qua mt tn hiu v tuyn. Cc trm qung b s dng mt anten c cng sut ln truyn sng v tuyn n khu vc xung quanh.Ngi xem c th thu c tn hiu vi mt anten nh. Hn ch chnh ca truyn hnh qung b l phm vi truyn sng. Cc tn hiu v tuyn c s dng cho truyn hnh qung b th c bn ra t cc anten pht sng trn mt ng thng. nhn c nhng tn hiu ny, bn cn c mt anten c tm nhn trc tip. Chng ngi vt nh nh cy hoc cc ta nh nh khng phi l mt vn , nhng mt tr ngi ln, chng hn nh Tri t , s phn nh nhng sng v tuyn. Nu tri t phng hon ton, bn c th chn ln truyn hnh qung b hng ngn dm t pha my pht. Nhng bi v Tri t c cong nht nh v n c th ph v tm nhn ca ng dy tn hiu. Cc vn khc vi truyn hnh qung b l tn hiu thng b bp mo, ngay c trong khu vc xem. c c mt tn hiu hon ton r rng nh truyn hnh cp th bn phi kh gn vi cc anten pht sng m khng c qu nhiu vt cn.

3. H thng truyn hnh v tinh Truyn hnh v tinh gii quyt cc vn v phm vi v s bin dng bng cch truyn tn hiu truyn hnh t v tinh quay quanh Tri t. K t khi v tinh c th bay cao trn bu tri, th c nhiu khch hng c ci nhn tt hn v thng tin v tinh. H thng truyn hnh v tinh truyn v nhn tn hiu v tuyn dng anten c bit gi l anten cho v tinh. Ban u, h s dng cc anten cho t tin ch xem cc chng trnh khng dnh cho cc khn gi i chng. Cc anten cho v thit b thu sng cho ngi xem l nhng cng c nhn c tn hiu t cc i nc ngoi, ngun cp d liu trc tip gia cc i truyn hnh khc nhau, cc hot ng ca NASA v rt nhiu th khc truyn bng cch s dng v tinh. Mt s ch s hu v tinh vn tm kim ny sp xp cc chng trnh ring ca h, nhng ngy nay, hu ht cc khch hng truyn hnh v tinh c c chng trnh ca h thng qua mt v tinh pht sng trc tip (DBS) nh cung cp, chng hn nh DirecTV hoc DISH Network. Nh cung cp la chn cc chng trnh v pht sng cho cc thu bao nh l mt gi thit lp. V c bn, mc tiu ca nh cung cp l mang li hng chc hoc thm ch hng trm knh truyn hnh ca bn trong mt hnh thc xp x vi cnh tranh, truyn hnh cp. Khng ging nh cc chng trnh trc , cc chng trnh pht sng ca nh cung cp hon ton l k thut s, c ngha l n c hnh nh v cht lng m thanh tt hn. Ban u Truyn hnh v tinh c pht sng bng tn C i pht thanh - i pht thanh trong 3,7 (GHz) di tn s 6,4 GHz. K thut s v tinh pht sng cc chng trnh trong di tn Ku (11,7 GHz n 14,5 GHz). C nm thnh phn chnh tham gia vo trc tip n nh (DTH) hoc h thng truyn hnh v tinh pht sng trc tip (DBS): ngun lp trnh, trung tm pht sng v tinh, anten cho v tinh v ngi nhn. Ngun chng trnh ch n gin l cc knh cung cp chng trnh pht sng. Cc nh cung cp khng to ra chng trnh gc ca chnh n, n tr tin cc cng ty khc (HBO, v d, hoc ESPN) quyn pht sng ni dung ca h thng qua v tinh. Bng cch ny, cc nh cung cp ging nh mt nh mi gii gia bn v cc ngun chng trnh thc t. Ti trung tm pht sng, cc nh cung cp truyn hnh nhn c tn hiu t ngun chng trnh khc nhau v to ra mt tn hiu pht sng cho cc v tinh trong qu o a tnh. Cc v tinh nhn c cc tn hiu t cc trm pht sng v pht li Tri t. Anten cho ca ngi xem chn tn hiu t v tinh (hoc nhiu v tinh trong cng mt phn ca bu tri) v chuyn n vo cc thit b thu trong nh. Nhn x l tn hiu v chuyn n vo mt truyn hnh tiu chun.

4. Cc u thu v tinh u thu DVB-S2 VTC-HD 08

PVR v TimeShift l 2 chc nng ni tri ca u thu VTC-HD08. Bng cch ci t hn gi hoc ghi hnh trc tip, PVR s lu tr chng trnh cn xem di nh dng file c th xem li trn Tivi bt c lc no bn mun. Trong khi chc nng TimeShift gip bn khng b l bt k chng trnh truyn hnh no. Ch cn n nt tm dng sau tr li n nt Play xem tip on chng trnh va b l. - Tng thch hon ton vi chun DVB-S/DVB-S2 v HD MPEG-2/4 (H264). - Tng thch hon ton vi tiu chun SD/HD MPEG-2/4 (H.264), VC1, DVB-S/DVB-S2 - H tr h thng kha m cao cp Irdeto - C th thu tn hiu v tinh trn c hai bng c v Ku theo chun SCPC v MCPC - T ng chuyn i gia h PAL/NTSC - C kh nng lu tr ln ti 4000 knh TV v Radio - C kh nng to 16 nhm chng trnh a thch khc nhau - Mn hnh hin th bng nhiu ngn ng, vi 32bit mu. - C kh nng hin th thng tin lch chng trnh trong 7 ngy (EPG) - H tr y iu khin DiSEqCl0/1.1; 13/18V; 0/22K - H tr nhiu chc nng qun l chng trnh nh: to nhm a thch, di chuyn, kha, i tn v sp xp - H tr kha tr em - T ng lu li danh sch chng trnh - C kh nng nng cp phn mm qua sng hoc USB - C kh nng ghi li chng trnh ang pht sng trc tip, xem li ni dung pht sng trc tip trc

- C kh nng xem nhiu nh dng file a phng tin khc nhau t cng hay USB ngoi; c th tua nhanh/lm chm file. u thu K+ B u thu v thit b gii m K+ SD mang nhn hiu Opentel ODS1400NA bao gm 1 u thu, 1 th gii m, 1 cho thu tn hiu v tinh, 1 LNB, 2 gic v 20 mt dy cp.

Thng s k thut:

phn 2: s nguyn l ca 3 khi chnh.I.

khi ngun.

1. cu to - cu ch: ngt khi dng in i vo qu ti. - cun kh t (Z101): kh t, chng nhiu. - t: lc nhiu. - Diode: chnh lu dng xoay chiu thnh dng 1 chiu.-

bin p xung: bin i in p c hiu xut cao.

- Opto: cch ly iu khin gia 2 tng mch in khc nhau. mc ch: nu c s c t tng ng dng nh chy, chp, tng p... th cng khng nh hng ti tng iu khin. - Transitor: khuch i dng.

-

IC n p LM317: a ra cc mc in p, gip h thng mch hot ng n nh.

2. nguyn l hot ng khi ta cp ngun 220vAC/50Hz vo mch, i qua cu ch qua cun kh t - n diode cu to ra ngun 1 chiu i qua t lc vo bin p xung, bin p xung hot ng i qua 1 lot diode ( ghim cc mc in p (+)) qua IC LM317 to ra cc mc in p nh: 3v, 5v, 12v... gip mch hot ng. 1 phn khi qua bin p xung n opto gip hi tip in p v cch ly iu khin gia 2 tng mch in khc nhau.

II.

khi vi x l.

1. c u to:-

b knh: t anten- khuch i cao tn- i tn RF/IF-bin i A/Dgii iu ch Q-PSK- sa li FEC.

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FEC ( forward error correction): y l phng php dng pht hin- sa li < li n gin>. Nguyn tc: thm vo gi tin c pht nhng phn d, phn d ny c tnh ton da trn thng tin c gi v kiu ca FEC. C 2 kiu FEC l m khi tuyn tnh ( linear block code) v m xon hay cn c gi l m tch chp ( convolution code). kh nng pht hin li v sa li cn ph thuc vo khong cch Haming cc tiu. mch vi x l/ gii nn MPEG-2: s dng 1 IC ln,4 hng chn, gi tt l IC chnh hoc IC vi x l, IC ny c tn l SC 2005 B. mch ny iu khin mi hot ng ca my, gii nn hinh MPEG2, gii nn ting MPEG-2. kt qu gii nn hnh MPEG-2 l cho ra cc tn hiu: video, chi Y, mu C. Cc tn hiu ny qua cc tng m ri ra cc sau my, kt qu gii nn ting MPEG-2 l cho ra cc tn hiu ting c dng s v tn hiu cp quang S/PDIF. Tn hiu ting dng s ny qua mch bin i D/A thnh tn hiu ting tng t 2 v tri (L) v phi (R), qua mch khuch i 2 v ri ra AUDIO OUT sau my.

-

- mch dao ng xung nhp: ng b tt c cc hot ng ca my. mch ny c th c to ra nh chnh IC vi x l hoc t 1 mch in ngoi IC chnh. - IC EEPROM: b nh ch c chng trnh, xo c bng in. L b nh c ni dung nh khng b mt i khi mt in. - IC nh SD RAM: b nh truy cp ngu nhin ng b. L b nh ghi v c, c ni dung nh b mt i khi mt in. - b bin i AV/RF: tn hiu audio v video iu ch sng cao tn RF thnh sng mang cao tn v truyn tn hiu ti tv bng dy cp ng trc. u vo l tn hiu ting (A) tn hiu hnh (V), u ra l tn hiu sng mang cao tn RF. 2. nguyn l hot ng:

-

khi ngun hot ng cp cho b vi x l. Tn hiu c thu nh anten thu b knh, ti b knh thc hin khuch i cao tn, i tn RF sang IF chuyn qua b gii iu ch bin i tn hiu tng t (A) sang tn hiu s (D), qua b gii iu Q-PSK n b sa li FEC. y ta c 1 card thng minh ( n nh 1 kho in t) th card do nh mng cung cp, mi nh mng cung cp 1 th card c cc bng tn khc nhau. Khi ta d ng tn s th th card m, a tn hiu ( MPEG-2) t b knh n IC vi x l, nu trong qu trnh truyn xy ra li IC chnh s t ng a tn hiu quay li b FEC qua bus iu khin. ti y FEC s t ng sa li v truyn li cho IC chnh. IC chnh hot ng s gii nn MPEG-2 a ra tn hiu chi Y, mu C v video. ng thi bin i D/A ting v khuch i 2 v ting L/R v a ra dc kt ni. IC chnh hot ng c cn nh vo dao ng xung nhp, IC nh SD ram v IC nh EEProm.

-

-

III.

khi hin th.

1.

cu to:-

IC 89S52: l IC vi iu khin c: 8k ROM, 128byte RAM, 32 ng xut nhp, 1 port ni tip v 2 b nh thi 16 bit. b led 7 thanh: b led ny gm 4 led 7 thanh c nh s nh s ln lt L1,L2, l3, l4, t tri qua phi. Cc chn ca DSP1 c k

-

hiu a,b,c,d,e,f,g, l tng ng vi 7 on ca led 7 thanh. Cc chn ny l chung cho c 4 led. Chn 5v va 2p l tng ng vi 2 chm nhp nhy gia hai den Led L3, L4. cho 1 thanh n led sng ln th phi c dng ngun vo chn l, m ngun vo cc chn a,b,... tng ng vi cc thanh . v d : mun dn led th 2 sng hin ln s 3 th: chn L2 =5v , cc chn a,b,c,d,g =GND (m ngun) mun cho chn 2 nhp nhy gia sng ln th chn L5=5v v chn 2p =GND cc n Q1,Q2,Q3,Q4 cp ngun cho 4 n led L1,L2,L3,L4 . khi cc b ca cc n ny c mc in p thp n n n thng - cp ngun cho led 7 thanh khong 4v n Q5 dng lm sng hai chm gia khi cc B ca Q5 c mc in p thp Q5 thng hai chm gia sng ln do c dng i t chn 5v qua diode quang hai chm gia qua Q5 qua R xung mt. V cc hot ng trong IC l cc tn hiu xung, nn cc n led 7 thanh sng c khng phi l do cp in lin tc m l cp in gin on. - Transitor: khuch i dng cho led. - IC s ( cng YES): iu khin nt nhn. - Nt nhn: iu khin knh, m lng, reset my. - Led hng ngoi: thu tn hiu t iu khin pht lnh. 2. nguyn l hot ng: thng qua rack kt ni b vi x l vi mch hin th, ( thch anh dao ng gip 89s52 hot ng). IC 89s52 lp trnh sn c cp ngun iu khin led 7 thanh, led 7 thanh s hin th knh m chng trnh lu t trc.-

TH1: iu khin t mt thn( led hng ngoi): khi iu khin ra lnh m ngun mt hng ngoi nhn tn hiu t iu khin t xa,

IC89s52 gii m lnh nhn c t iu khin, sau gi n b vi x l, b vi x l- x l v thc hin lnh v gi tn hiu li 89s52 iu khin chc nng hin th trn led 7 thanh.-

TH2: iu khin t nt nhn: khi ta nhn ngun iu khin m knh, nt nhn c iu khin bi IC s (cng YES) cho php m. Knh c lu sn trong b knh vi cc m knh t sn ph hp vi th card. Tn hiu c i n b vi x l, ti y b vi x l gii m v tr v tn hiu nhn c hin th trn led 7 thanh, nh IC 89s52 iu khin hin th.

phn 3: li thng gp v cch khc phc.

TT M t li 1

2

3

Nguyn Cc khc phc nhn u thu khng thu -Tn hiu n - Kim tra li u ni nten, kim tra nten xem c c chng trnh ten vo hng v i pht hay khng, cp anten c b t hay no, hin th thng cha tt khng ? bo E48 Khng hoc khng - Sau khi sa cha v khc phc s c, Kim tra mc c tn c tn hiu tn hiu: vo Menu --> Ci t ngi dng --> D hiu hoc E52- vo t nten chng trnh. Nu phm cht tn hiu trn 70% l ang d tn hiu t yu cu. u thu khng thu -Tn hiu n - Kim tra mc tn hiu: vo: Menu --> Ci t c chng trnh ten vo ngi dng --> D chng trnh. Nu phm cht no, hin th thng cha tt tn hiu thp (di 70%), cn kim tra v khc ph bo E50 Khng -Hoc c li nten, u ni v dy cp (nten cha hng v c dch v gin on t pha i pht, cp b t, u ni b hng...) i pht - Nu phm cht tn hiu n nh v trn 70%, chng trnh b gin on t i pht. bn khng cn iu chnh my thu hoc nten, ch cho i pht khc phc s c. u c mt s -Tn hiu n Kim tra mc tn hiu: vo: chuyn u thu v chng ten vo chng trnh khng thu c Menu --> Ci t trnh khng thu cha tt ngi dng --> D chng trnh. Nu phm cht c, hin th thng - Hoc c tn hiu thp (di 70%), cn kim tra v khc phc bo E50 Khng gin on t li nten, u ni v dy cp (nten cha hng v c dch vkhi i pht pha i pht, cp b t, u ni b hng...) chuyn sang chng - Nu tn hiu tt, phm cht trn 70%, nu chng trnh trnh l chng trnh khng kho m, c gin on chng trnh t i pht. Bn khng cn iu chnh my thu, v ch i pht khc phc s c - Nu tn hiu tt, phm cht trn 70%, chng trnh l chng trnh kho m (c hin th du $): Chuyn u thu v chng trnh b li, bm Menu--> H thng kha --> Thng tin kha m. Kim tra cc dng thng tin: - Dng thng tin th 2 M dch v: Nu hin th No card: Cha c m dch v. Nu c m dch v s hin th: 401349.... --> Kim tra dng thng tin s 7,EMM PID , nu gi tr l 1FFF, u thu cha nhn m dch v --> Tt bt li u thu hoc lin h vi b phn k thut c tr gip. ---> Nu dng th 7 hin th 0500,kim tra dng thng tin th 8,Service Information, nu Service information hin th: - E16: Dch v cha c kch hot - E30: Dch v ang c khi to, xin ch! --> tt u thu i bt li - E29: Dch v ang hot ng -->, chng trnh ang b gin on t i pht.