MO PHI TUYN V CC BIN PHP KHC PHCGio vin hng dn: TS Phm Xun NghaHc vin thc hin:1. Th Sen2. Vn Tho3. Phm Thanh Thng4. Phm nh Vit

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MO PHI TUYNNi dung nghin cu:- Cc yu t nh hng n cht lng HTTT VT- Khi nim mo phi tuyn- nh hng ca mo phi tuyn- Mt s loi b khuch i dng trong thng tin v tinh- M phng nh hng v cc gii php khc phc mo phi tuyn*/20

CC YU T NH HNG N TTVT*/20Suy hao trong khng gian t doSuy hao do maSuy hao do tng in ly, tng i luSuy hao do mt ng chnh antenSuy hao do nhit tp m h thngNhiu do trm vi ba Nhiu do cc v tinh bn cnh

SUY HAO TRONG KHNG GIAN T DO/20

SUY HAO DO MALrain: T l tn hao cng sut tng ng Tg : Nhit ca b hp th biu kinTrain : Nhit tp m do ma gy ra

/20Do b dy ca dt nc c dng hnh dt nn suy hao khi i qua ht ma gia phn cc ng v phn cc ngang l khc nhau, v vy u thu ta thu c tn hiu thng ging do cng sut thu c gia phn cc ng v phn cc ngang khc nhau.

SUY HAO DO TNG IN LYSng v tuyn in trong thng tin v tinh ngoi suy hao ng truyn do c ly xa cn nh hng do tng in ly v kh quyn .

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NHIU DO TRM VIBA MT T/20

NHIU DO V TINH BN CNH/20ng xung can nhiu sy ra do anten pht ca v tinh 2 chiu vo trm thu 1 v anten thu ca trm 1 cng thu c hng ca v tinh 2

Cc loi b K dng trong thng tin VT- Mt s loi b khuch i thng dng :+ B khuch i cng sut cao dng bn dn (SSPA) vi cng sut t 1W 10W+ B khuch i cng sut dng dn sng chy*/20

B khuch i cng sut TWT- B K TWT c bng tn K rng, h s K cng sut in hnh t 25 n 50 dB.- TWT c s dng ph bin cho cc tng KDCS cao cc trm mt t

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B KCS dng bn dn- Cng ngh transistor hiu ng trng Gali v Asen gi vai tr quan trng trong thng tin VT. - SSPA ngy nay c kh nng thay th TWT trong cc mch khuch i cng sut nh cc trm mt t v to ra cc b pht p mi.*/20

MO PHI TUYN- Mo phi tuyn gy bi cc phn t phi tuyn (khng tha mn tnh cht xp chng, c c tuyn vo-ra l mt ng khng thng).- Cc ngun gy mo+ Cc mch khuch i cng sut nh (mo phi tuyn c th b qua)+ Cc mch khuch i cng sut ln (HPA)+ Mch trn (mixer) s dng diode+ Mch hn bin

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MO PHI TUYN- Mo phi tuyn gy ra do b KCS ln+ Tn hiu u vo ca b KCS l x th tn hiu ra sau b KCS s l y:

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NH HNG CA MO PHI TUYN+ Tri rng ph v gy tp m phi tuyn

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NH HNG CA MO PHI TUYN/20+ Gy mp chm sao tn hiu v gy ISI phi tuyn

Cc bin php khc phc mo phi tuyn1. S dng back- off ti u (BO- li cng sut ti u)2. S dng quay pha ph ti u sng mang thu3. S dng mo trc*/20

1. S dng back-off ti uChn im lm vic mc tn hiu tng i thp, tc l chp nhn mt li cng sut ln tnh t cng sut bo ha ca b khuc i*/20

2.S dng quay pha ph ti u sng mang thuMo phi tuyn lm dch chuyn im tn hiu nn phng php ny l quay pha theo s quay ca mo. Phng php ny ch khc phc c s quay cn vic gim bin th khng khc phc c.*/20

3.S dng mo trcNhim v ca b mo trc l o chc nng phi tuyn ca b khuch i cng sut cao HPA, nh vy tng p ng ca hai thit b l tuyn tnh. */20

S dng mo trc*/20

S dng mo trc*/20

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