141623663 Cac Mach Vong Khoa Pha

LOGO

II : CC MCH VNG KHA PHA (PLL)

1: Tng quan PLL ( Phase-Locked Loop )

- L h thng vng kn hi tip

- Tn hiu vo c th c dng tng t hnh sine hoc dng s.

- ng dng rng ri trong cc mch lc, tng hp tn s, iu ch v gii iu ch, iu khin t ng . . .

- C rt nhiu kiu mch PLL v phc v cho nhiu mc ch

LOGO 2: S khi

LOGO 2: S khi

Tch sng pha: So snh tn hiu vo v tn hiu ra ca VCO to ra tn hiu sai lch Vd(t).

Lc thng thp: Lc gn ca in p Vd(t)

Khuch i mt chiu: Khuch i in p mt chiu Vdk(t).

VCO(Voltage Controled Oscillator): B dao ng m tn s ra c iu khin bng in p a vo.

LOGO 3: Hot ng ca mch

Nguyn l hot ng

Cc thnh phn ca PLL

VCO (Voltage controlled oscillator )

Hot ng ca mch

Khuch i mt chiu


1: Nguyn l hot ng

- Hot ng theo nguyn tc vng iu khin m i lng vo v ra l tn s, chng c so snh vi nhau v pha.


Di bt Bc (Cature range): Bc = f2 f1

- Di tn s m tn hiu vo ban u phi lt vo PLL thit lp ch ng b.

- Bc ph thuc vo bng thng LPF.


Di kha Bl: K hiu Bl = fmax fmin.

- Gii tn s m PLL ng nht c tn s f0 vi f1.

- Ph thuc hm truyn t ca b tch sng pha, khuch i, VCO.

- Khng ph thuc vo p tuyn b lc LPF v PLL (khi PLL kha pha f1 - f0 = 0).

- ch kha pha, dao ng f0 ca VCO bn ng b theo f1 (Bl > Bc).


Cc thnh phn ca PLL

- B tch sng pha: C 3 loi

- Tng ng dng mch chn

- S thc hin bi mch s EX-OR,RS FlipFlop

- Tch sng pha ly mu

- B tch sng pha tng t


Ng ra ca in p c:


B tch sng pha s:

- Dng mch s EX-OR, R-S Flip Flopc p tuyn so snh pha dng:


Lc thng thp LPF:

- Mch lc bc 1, c th dng th ng hoc tch cc

- Ng ra gm nhiu thnh phn f0,f1,f1-f0,...

- Hot ng chnh xc khi f0,f1 thp.


Khuch i mt chiu

- Khuch i tn hiu bin i chm (DC) sau b lc thng thp LPF. li Ka


VCO (Voltage controlled oscillator)

- Mch dao ng c tn s c kim sot bng in p.

- Quan h in p iu kin Vdk(t) v tn s ra f0(t) phi tuyn tnh.

- V nguyn tc c th dng mi mch dao ng. Tuy nhin cc b dao ng to xung ch nht c s dng rng ri v loi ny c th lm vic t 1MHz 100MHz


VCO (Voltage controlled oscillator)

- T 1MHz 50MHz thng dng mch dao ng a hi.

LOGO 4: ng dng ca vng kha pha PLL

ng dng ca vng kha pha PLL

S Dng Trong

FM

Stereo

Gii iu Ch AM

ng B Tn S Ngang

V Dc Trong

TV

Gii iu Ch FSK

Gii iu Ch FM

B Tng Hp Tn S n


B tng hp tn s n

- S dng cc b tng hp tn s da trn nguyn l vng kha pha PLL

- u im nh gn, khng yu cu chnh xc c kh cao, ng dng cc thnh qu cng ngh sn xut vi mch. . .

- ng thi khi kt hp vi thch anh, n c kh nng to ra di rng, chnh xc cao, gi thnh thp. . .


- Khi PLL thc hin kha pha, th ta c:

fref =fvco / N => fvco = N*fref = f0

B iu khin tn s ny c th c iu khin d dng nh my tnh, t xa. Gim gi thnh v phc tp so vi trc y


- Khuyt im l n ch to ra cc tn s bng bi s ca tn s chun f0= N*fref

- Khc phc bng cch chia nh t/s chun


Gii iu ch FM

- Thc hin bng cch ci t tn s dao ng t do fn bng tn s trung tm tn hiu FM ng vo c bin khng i

- Trong nhiu ng dng c th, trc tch sng pha PLL c mch khuch i hn bin


Gii iu ch FSK

- Dng c bit ca FM, ch c 2 tn s iu tn. Lin quan n tch (gii m) tn hiu quay s in thoi nt nhn v truyn tn hiu s FSK

- Ng ra ca PLL dng 2 mc in p


ng b tn s ngang dc trong TV


Gii iu ch AM


Gii iu ch AM

- Vo(t) t l vi m(t) tc l t l vi tn hiu gii iu ch AM

- L kiu tch sng trc tip khng cn i tn, c u im khng dng trung tn, khng chn lc tn s nh.

- bin tn hiu ra ln nht ta dng b tch sng ng b


Gii iu ch AM

- Tch sng ng b c cht lng tch sng khng ng b khi t s S/N nh


S dng trong FM Stereo

- S khi my pht FM Stereo



- Ph ca tn hiu FM Stereo



- S khi my thu FM Stereo



- ng dng PLL trong vic gii m FM Stereo

Documents

141623663 Cac Mach Vong Khoa Pha