Microsoft PowerPoint - 3RFSystem.ppt [호환 모드]

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1 Transceiver rchiecures 김영석 충북대학교전자정보대학 전자정보대학김영석 3-1

2 Conens 3. Modulaion and Deecion 3.1 General Consideraions 3. nalog Modulaion M, PM, FM 3.3 Digial Modulaion BPSK, BFSK, QPSK 5. Transceiver rchiecures 5. Rx rchiecures Heerodyne, Homodyne, Image-Rejec, Digial-IF, Subsampling 5.3 Tx rchiecures Direc-Conversion, i To-sep 전자정보대학김영석 3-

3 3.1 General Consideraions (Modulaion Definiions (a Baseband Signal: One hose specrum is non-zero in he viciniy of =0 and negligible elsehere (b Passband Signal: one hose specrum is non-zero in a band around a carrier frequency c and negligible elsehere x( = a( cos[ c + θ ( ] Modulaion convers a baseband signal o i s passband counerpar, for ease of ransmission (e.g. anenna size Demodulaion exracs he baseband signal Modulaion/Demodulaion Schemes = Modem Imporan specs of Modems Qualiy: SNR, or bi error rae Bandidh: Specral Efficiency Poer Efficiency 전자정보대학김영석 3-3

4 3. nalog Modulaion: mpliude Mod. For a baseband signal x b (, he ampliude modulaed signal is x M ( = [1 + m x Can be generaed ih a mixer c BB ( ] cos c Passband signal has ice he bandidh of he baseband signal Demodulaion: mix ih carrier and LPF, or use an envelope deecor 전자정보대학김영석 3-4

5 3.. Phase and Frequency Modulaion Phase and Frequency are relaed by = dφ / d Phase modulaed signal is expressed as (m=phase mod. Index x ( = cos[ mx ( ] PM c c + BB Frequency modulaed d signal is expressed as x FM ( = c cos[ c + m x BB ( d] 전자정보대학김영석 3-5

6 Modulaion/Demodulaion Frequency Modulaion can be done by varying he freq. of an OSC ih he baseband signal Frequency Demodulaion can be performed by freq. sensiive ck, commonly by a PLL 전자정보대학김영석 3-6

7 3.3 Digial Modulaion Mos modern ireless sysems use digial modulaion due o is advanages over analog modulaion Qualiy of RF sysems is evaluaed by BER(bi error rae. Modulaion mehods are compared according o heir probabiliy of error (Pe 전자정보대학김영석 3-7

8 3.3. Basic conceps Basis funcions: any modulaion scheme can be represened by a se of orhogonal basis funcions T Def. orhogonal: φ ( φ ( d = 0 s E.g. FSK(Frequency shif keying x FSK ( = α 1 φ 1 ( + α φ ( here[ α, α ] = [0 ] for a1and [ 1 c basis funcions φ ( = cos, φ ( = cos 1 1 c 0 m k 0] for a 0 Signal consellaions: modulaed aveforms can be vieed in erms of heir coefficiens and basis funcions Each basis funcions conribues one axis o he plo 전자정보대학김영석 3-8

9 3.3. Basic conceps Opimum deecion: I can be shon ha he opimum deecor is a correlaor, hich can be buil by a muliplier (mixer folloed by an inegraor (p(=pulse shape Inegraion produces an averaging ha reduces he effecs of he noise 전자정보대학김영석 3-9

10 Digial Modulaion BPSK(Binary Phase Shif Keying x BPSK ( = c cos( c + φ here φ = 0 or 180 x ( = α cos hereα = + c or c BPSK c P e, BPSK = Q( E N 0 b here E b is he average energy per bi and N0 is he poer specral densiy of he addiive i hie Gaussian noise 전자정보대학김영석 3-10

11 Digial Modulaion BFSK(Binary Frequency Shif Keying x BPSK ( = α1 cos 1 + α cos here [ α α ] = [0 ] or [ 0] 1 c c P e, BPSK = Q( E N b 0 here E b is he average energy per bi and N0 is he poer specral densiy of he addiive i hie Gaussian noise 전자정보대학김영석 3-11

12 Digial Modulaion Quadraure Modulaion: basis funcions (a QPSK(Quadraure Phase Shif Keying Send bis ih one symbol QPSK here [ α α ] = [ cos and sin x = α cos + α sin c ( 1 c c ], [- c ],[ - ],[- - ] 1 c c c c c c c c P e, BPSK = here E b Q( E N 0 b is he average energy per bi and N 0 is he poer specral densiy of he addiive hie Gaussian noise problem ih QPSK is he sharp ransiions => OQPSK or π/4- QPSK 전자정보대학김영석 3-1

13 5. Receiver rchiecures Why no perform Channel Selecion and Demodulaion a he RF? Tuneable Filers are harder o realize Very High Q Channel Selec Filer a f c is needed Q=f c /Δf Ex: IS-54, 30kHz, 900MHz, 60dB enuaion a 45kHz offse, nd -order LC filer Q=10 7 (Impossible Donconvering RF o IF before Channel Selecion using a variable VCO => Use a fixed, lo-q filer (lo f c, same Δf 전자정보대학김영석 3-13

14 Herero=differen, dyne=mix 5..1 Heerodyne Receivers RF o IF(Inermediae Frequency by Donconversion Mixing High Q Filer is no required Inclusion of LN o loer he Noise Figure 전자정보대학김영석 3-14

15 Problem of Image Signal and Image are donconvered o he same frequency Ho o suppress he Image: Image-Rejec Filer 전자정보대학김영석 3-15

16 IF Selecion Trade-off beeen Image Rejecion and Channel Selecion High IF: Beer Image Rejecion Lo IF: Beer Channel Selecion Oher facors: vailabiliy, Physical Size of IF filers High or Lo-side Injecion Lo-side: Minimize LO freq High-side: Reduced Tuning Range for he VCO 전자정보대학김영석 3-16

17 Dual-IF Topology To Lessen he rade-off beeen Image Rejecion and Channel Selecion, a Dual-IF is used 1 s -mixer convers o a relaively high IF o allo Image Rejecion nd -mixer convers o a lo IF o allo Channel Selecion 전자정보대학김영석 3-17

5.. Homodyne Receivers Homodyne, Direc-Conversion, Zero-IF rchiecure Only LPF is required for channel selecion Topology (a : Double-sideband M (Same

18 5.. Homodyne Receivers Homodyne, Direc-Conversion, Zero-IF rchiecure Only LPF is required for channel selecion Topology (a : Double-sideband M (Same informaion on boh sides of he specrum Topology (b (Quaraure Donconversion: FM or PM (Differen informaion on he differen sides of he signal 전자정보대학김영석 3-18

19 dvanages No Image Filer No IF SW filer Single Chip Rx (IC Drabacks DC Offses I/Q Mismach Even-order Disorion Flicker Noise Homodyne Receivers 전자정보대학김영석 3-19

20 DC Offses DC Offse Volages resul from Self-mixing due o Poor isolaion beeen LO and RF during donconversion Example: Inpu RF = 1μVrms ( => Mix oupu RF = 30μVrms (30dB LO = 0.63V (0dBm => LO leakage = 0.63mV (60dB Isolaion => Mix oupu DC offse = 10mV (30dB gain => Sauraes he gain sages (50-70dB gain 전자정보대학김영석 3-0

21 Soluions for DC Offses High Pass Filering o remove DC offses Coding is required o remove he informaion a DC Lo Cuoff Frequency => Large C Wases Specrum Perform Periodic Offse Cancellaion Periodically sample he signal and cancel i Works bes for TDM Sysems Mos common soluion 전자정보대학김영석 3-1

22 I-Q Mismach Mismach in gain and phase beeen I/Q LO signals => gain and phase error in he received signal consellaion Eg. for QPSK signal RF : x ( = a cos( + bsin( i( here a, b = ± 1 I c Q ε θ LO : v LO, I ( = (1 + cos( c + ε θ vlo, Q ( = (1 sin( c ε θ ε θ IF( afer mixing : xbb, I ( = a(1 + cos b(1 + sin ε θ ε θ xbb, Q ( = a(1 sin + b(1 cos c mpliude mismach < 1dB, phase error < 5deg 전자정보대학김영석 3-

23 Even-Order Disorion Like 3 rd -order disorion (IP3, nd -order Nonlineariy of mp is problemaic in homodyne To High-freq inerferers generae a lo-freq bea in he presence of even-order disorion => Direc feedhrough from RF o IF (lo- freq bea muliplied by cos LO is ranslaed o high freq: no a problem RF : x ( = cos( + cos( 1 LN oupu : y( = α x( + α x 1 1 ( =... + α 1 cos( 1 Differenial circui opologies ill help suppress nd -order disorion 전자정보대학김영석 3-3

24 Flicker Noise Donconvered (afer only amplified by LN and mixer lo-freq signals are influenced by 1/f of nex sages Despie all of hese difficulies, homodyne receivers become more common Due o high levels of inegraion Sandard in some applicaions (eg. pagers 전자정보대학김영석 3-4

25 5..3 Image-Rejec Receivers 90deg phase shif = muliply he specrum by G(=-j*sgn( Eg. sin => -cos (90deg phase shif j sin( = e 1 cos( = e j + j j e 1 j e j 전자정보대학김영석 3-5

26 Harley rchiecure ssume lo-side injecion i( i( ( cos cos ( x im RF im LO LO RF im im RF RF + = + = sin( sin( sin( sin( ( x im LO im LO RF RF im LO im RF LO RF + = + = cos( cos( ( cos( cos( ( x x im LO im RF LO RF B im LO im RF LO RF C + = = (Image componens cancel ou cos( ( ( ( x x x RF LO RF B C IF = + = 전자정보대학김영석 3-6

27 Harley rchiecure 90 deg phase shif is replaced ih +45 shif in one pah and -45 shif in he oher 전자정보대학김영석 3-7

28 Harley rchiecure Gain and phase mismach ill lead o incomplee image rejecion Eg. x LO1 ( = LO sin LO, LO P IRR(Image Rejecion Raio = P x im P sig ( = ( LO ( ε / LO + ε cos( 4 + θ LO + θ In mos RF applicaions, IRR=60-70dB is required For ypical maching in IC, gain mismach=0.-0.6db,.6db, phase imbalance=1-5deg, IRR=30-40dB So, Image Rejec Filer mus sill be used 전자정보대학김영석 3-8

29 Weaver rchiecure To avoid 90 deg phase shif (problemaic, an alernae image rejec archiecure can be used. Secondary Image problem 전자정보대학김영석 3-9

30 5..4 Digial-IF Receivers fer iniial donconversion, use DC o digiize he signal and perform second mixing and filering in he digial domain dvanages: No I-Q mismach, maximum flexibiliy 전자정보대학김영석 3-30

31 5..5 Subsampling Receivers Subsample he RF signal a he Nyquis rae (lo LO Filer he resuling oupu, eliminaing he need for a mixer Meris: simplify he design of he LO Demeris: Noise aliasing (Subsampling by a facor m => Increase he noise poer by a facor m 전자정보대학김영석 3-31

5.3 Transmier rchiecures Tx archiecures are generally much less varied, because noise, inerference rejecion, and band seleciviy are more relaxed. 5.3.1

32 5.3 Transmier rchiecures Tx archiecures are generally much less varied, because noise, inerference rejecion, and band seleciviy are more relaxed Direc-conversion Transmier LO pulling: P oupu couples o LO, corruping is oupu by pulling i o a differen frequency pulling i o a differen frequency 전자정보대학김영석 3-3

33 5.3. To-sep Transmiers P frequency (1+ is differen from LO frequency (1 (no LO pulling 전자정보대학김영석 3-33

34 References Behzad Razavi, RF Microelecronics, Prenice Hall, Inc, 1998 전자정보대학김영석 3-34

11 주차 M 진디지털변조 (1) 통과대역신호의표현 (2) Quadrature Phase Shift Keying (QPSK) (3) Minimum Shift Keying (MSK) (4) M-ary Amplitude Shift Keying (M-ASK) (5) M-ar

11 주차 M 진디지털변조 (1) 통과대역신호의표현 (2) Quadraure Phase Shif Keying (QPSK) (3) Minimum Shif Keying (MSK) (4) M-ary Ampliude Shif Keying (M-ASK) (5) M-ary Frequeny Shif Keying (M-FSK) (6) M-ary Phase Shif Keying