vn KythuatTanSoTrucTiep DDS

Embed Size (px)

Text of vn KythuatTanSoTrucTiep DDS

TM TT NI DUNG

ti hng ti mt ci nhn tng quan v k thut tng hp tn s trc tip (DDS). Trong phn u, ni dung cp ti s cu to v gii thch nguyn l hot ng ca mt h thng DDS (Direct Digital Syntherizer). Khi xem xt ton b h thng DDS th mi quan h gia ph u ra ca h thng v nhiu do nh hng ca ly mu, ti to tn hiu, v do cc hn ch phi chp nhn khi trin khai thc t l vn u tin c quan tm tm hiu. Tip l vn sai s, cc ngun gy sai s v nh hng ca sai s ti hiu nng tn hiu k sinh, vn iu ch tn hiu,b lc trit mo, b lc FIR, b lc IIR, b lc polyphase..Nhng ng dng iu ch l mt phn khng th thiu khi nghin cu k thut DDS, v vy phn sau ti trnh by mt s vn v iu ch FSK, PSK, QAM dng DDS. Ngoi nhng vn l thuyt trn, ti cng dnh mt s trang minh ha nhng u im ni bt ca k thut DDS, nhng xu th pht trin nhm hon thin cng ngh DDS v nhng tin b t c ca mt h thng tch hp cng ngh DDS.

i

MC LCM U...............................................................................................................1 CHNG 1: NHNG IU C BN V K THUT DDS.......................21.1Nhng u im ca DDS..........................................................................................2 1.2L thuyt hot ng..................................................................................................2 1.3Xu hng tch hp chc nng...................................................................................5

CHNG 2: LY MU U RA V KH NNG CHUYN PHA V TN S CA THIT B DDS...........................................................................72.1Ly mu u ra thit b DDS.....................................................................................7 2.2Kh nng chuyn pha v tn s ca DDS.................................................................8 3.1Xc nh tc iu chnh ti a..........................................................................9 3.2Giao tip iu khin DDS.....................................................................................9

CHNG 3: VN NHIU TRONG H DDS.........................................113.1Tc ng ca phn gii DAC ln hiu nng nhiu vt (spurious performance)..11 3.2Tc ng ca oversampling) ln hiu nng nhiu vt.............................................12 3.3Tc ng ca ct gim trong b tch ly pha ln hiu nng vt (spur)....................13 3.3.1Bin cc vt.................................................................................................14 3.3.2Phn b cc vt to bi s ct pha....................................................................15 3.3.3Tm tt v ct b phase....................................................................................18 3.4Cc ngun gy ra cc vt khc ca DDS.................................................................19 3.5Hiu nng vt gii rng...........................................................................................20 3.6Hiu nng vt gii hp............................................................................................21 3.7D bo v khi thc vt sweet spots trong di iu chnh ca DDS....................21 3.8Xem xt s bin ng (Jitter) v n pha trong h thng DDS.................................21 3.9Xem xt b lc u ra.............................................................................................24 3.9.1p ng ca h Chebyshev..............................................................................27 3.9.2p ng ca b lc h Gauss...........................................................................28 3.9.3p ng ca h Legendre.................................................................................29

CHNG 4: NG DNG IU CH S CA DDS..................................314.1L thuyt iu ch s c bn...................................................................................31 4.1.1Cc khi nim c bn.......................................................................................31 4.1.2iu ch...........................................................................................................33 4.2Kin trc h thng v yu cu.................................................................................35

ii

4.3B lc s.................................................................................................................36 4.3.1B Lc FIR.......................................................................................................36 4.3.2B lc IIR.........................................................................................................38 4.4DSP a tc..............................................................................................................39 4.4.1Tng tc............................................................................................................40 4.4.2Gim tc...........................................................................................................41 4.4.3Chuyn i tc vi t s n/m.......................................................................43 4.4.4B lc s...........................................................................................................43 4.5Xem xt ng b d liu vo v xung.....................................................................47 4.6Cc phng thc m ha d liu v trin khai DDS...............................................49 4.6.1M ha FSK.....................................................................................................49 4.6.2M ha PSK.....................................................................................................50 4.6.3M ha QAM...................................................................................................51 4.6.4Quadrature up-conversion................................................................................52

CHNG 5: MT S KT QU THC NGHIM...................................545.1Gii thiu chip DDS AD9835.................................................................................54 5.2.1L thuyt hot ng..........................................................................................54 5.2.2Giao tip vi vi iu khin...............................................................................55 5.2.1S nguyn l................................................................................................56

KT LUN........................................................................................................60

DANH SCH CC HNH V

iii

HNH 1: S MT B TNG HP TN S TRC TIP N GIN ...............................................................................................................................3 HNH 2: H THNG DDS C TH IU CHNH TN S.......................3 HNH 3: TN HIU CHUYN QUA MT H DDS......................................4 HNH 4: KIN TRC DDS 12 BT VI CC CHC NNG PH.............5 HNH 5: PHN TCH PH U RA CA DDS............................................7 HNH 6: TC NG CA PHN GII DAC.......................................11 HNH 7: TC NG CA OVERSAMPLING LN SQR.........................12 HNH 8: SAI S DO CT BT V BNH PHA.......................................13 HNH 9: MU T IU CHNH C MC VT CC I......................14 HNH 10: MU T IU CHNH KHNG GY RA PHASE TRUNCATION SPUR......................................................................................15 HNH 11: DY TCH LY PHA....................................................................15 HNH 12: HOT NG CA T CT B..................................................17 HNH 13: PH CA DY T B CT B...................................................18 HNH 14: VNG NYQUIST V NH XA CA CC TN S BN NGOI BNG NYQUIST................................................................................19 HNH 15: TC NG CA S BIN NG XUNG H THNG..........23 HNH 16: PH U RA DDS.........................................................................24 HNH 17: B LC ANTI-ALIAS...................................................................25 HNH 18: P NG MIN THI GIAN......................................................25 HNH 19: P NG MIN TN S.............................................................26

iv

HNH 20: P NG CA CC B LC H CHEBYSHEV....................27 HNH 21: P NG B LC H GAUSSIAN...........................................29 HNH 22: P NG H LEGENDRE..........................................................29 HNH 23: PH BNG THNG C S MT PHA...................................32 HNH 24: PH BNG THNG C S HAI PHA.....................................32 HNH 25: PH BNG C S PHC............................................................32 HNH 26: PH BNG THNG DI..............................................................33 HNH 27: CU TRC IU CH C BN.................................................34 HNH 28: CU TRC IU CH S C BN...........................................34 HNH 29: CU TRC IU CH DDS C BN........................................35 HNH 30: B IU CH DDS........................................................................35 HNH 31: B LC FIR DNG N GIN..................................................36 HNH 32: P NG TN S B LC FIR CHO A0 = A1 = 0.5..............37 HNH 33: B LC FIR N-TAPS....................................................................37 HNH 34: B LC IIR N GIN...............................................................38 HNH 35: B LC IIR NHIU TAP..............................................................39 HNH 36: B TNG TC N GIN..........................................................40 HNH 37: S TNG TC BIU DIN TRONG MIN TN S..............40 HNH 38: B GIM TC N GIN..........................................................41 HNH 39: QU TRNH TNG TC XEM TRONG MIN TN S........42

v

HNH 40: B CHUYN I TC N/M.................................................43 HNH 41: B TCH PHN V B COMP C BN...................................44 HNH 42: P NG TN S CA B LC CIC C BN......................45 HNH 43: TNG TC V H TC DNG CIC.........................................45 HNH 44: P NG TN S CA B LC CIC C BN......................46 HNH 45: B TNG TC TRIPLE CASCADE CIC...................................46 HNH 46: B GIM TC CIC TR GP HAI...........