Hardware Technologies for Robust Personal Communication Transceivers

Transcription

1 Hardware Techologies for Robust Persoal Commuicatio Trasceivers Hery Samueli Asad A. Abidi Gregory J. Pottie Yahya Rahmat-Samii Itegrated Circuits & Systems Laboratory Electrical Egieerig Departmet Uiversity of Califoria Los Ageles, CA

2 UCLA Low-Power Trasceiver Program Objective: Low-power, hadheld, robust trasceivers for idoor ad mobile persoal commuicatios Meas: Ivestigate aalog, digital, ad atea techologies, coupled tightly to system desig Up to 160 kb/s Robustess Space Diversity with Multiple Ateas Frequecy Diversity with Spread-Spectrum Time Diversity with ECC/Iterleavig Low Power Dissipatio Low-Voltage Custom Aalog & Digital CMOS Moolithic CMOS 915 MHz Receive/Trasmit Path Two-chip Desig; Miimum Discrete Compoets

3 The UCLA Frequecy-Hopped Spread-Spectrum CMOS Trasceiver Basebad Data I Frequecy Cotrol Logic Frequecy & Timig Acquisitio DDFS DDFS 10b 10b 915 MHz Local Oscillator Limiter LPF SSB Select 90 PA Power Cotrol LNA BPF Basebad Data Out FSK Detector Digital Limiter Limiter LPF Aalog LPF BPF 90 LNA Limiter LPF

4 Performace Specificatios of Hadset Power Dissipatio of Hadset 225 mw i receive, 300 mw i trasmit Frequecy Bad Radiated Power Data Rate Duplexig Multiple Access Method Codig Modulatio Power Supply IC Techology Receive Ateas MHz (ulicesed ISM bad) 20 mw (max); 20 µw (mi) 2 to 160 kb/s (variable) Time Divisio Duplex betwee TX ad RX Frequecy-Hopped Spread-Spectrum CDMA Rate-½ Covolutioal Code (k=6) Biary or Quaterary FSK 3 V (max) 1-µm bulk CMOS Multiple miiature embedded elemets with space ad polarizatio diversity

5 Spread-Spectrum Systems: Hardware Implicatios Direct Sequece Frequecy Hopped Frequecy Diversity by makig chiprate >> symbol rate Covers wide badwidth with low hop-rate Equalizatio at chip-rate Highspeed sigal processig required Coheret receiver most commo Equalizatio at hop-rate oly Simple biary FSK modulatio may be used Mai advatage: SNR gai with coheret detectio, optimum modulatio Limitatio: High complexity No-coheret receiver is simple Mai advatage: Low-power receiver Limitatio: Sub-optimal chael capacity

6 Diversity Techiques Multiple Ateas Ateas receive ucorrelated sigals Use space ad polarizatio diversity Frequecy Spreadig Code-Divisio Multiple Access (CDMA); Direct Sequece OR Frequecy Hop Time-Divisio Multiple Access (TDMA); Equalizatio Time Diversity Codig Iterleavig Power Cotrol

7 Power Amplifier Switched Selectio FETs 3V 3V 75H MHz from modulator 75µm 8µm 16µm 32µm 64µm 128µm 256µm 0.7pF 3V 13H 1-µH Choke DRF 100W Atea Other half of quasi-differetial power amplifier Amplifier attais 42% power coversio efficiecy at +15 dbm output power Biary-weighted array of FETs gives 36 db of power cotrol (6-b word) Iductively-loaded preamp drives FETs above 3-V supply Off-chip matchig etwork filters out harmoics

8 Frequecy-Hopped Sythesizer Direct Digital Frequecy Sythesizer Circuits implemeted o this prototype Frequecy Cotrol Word (11b) Phase Accumulator (11b) SINE ROM COSINE ROM I Q 10b DAC 10b DAC Ati-alias Filter Ati-alias Filter I 915 MHz Local Osc Q F/H S/S SSB Sig Select Cotrol DDFS produces samples of a siewave at a frequecy selected by 11-b word; istatly agile frequecy source DDFS output rage is 0 13 MHz; addig up-coverted outputs produces SSB MHz; subtractig them produces MHz 8-b matchig required betwee chaels for adequate image suppressio

9 10-b, 80 MHz D-A Coverter φ1 φ2 φ3 0.5 pf Pipelie Delay Data Registers LSB LSB 3 bits (Word N) 3b (N) Charge Redistributio DAC 1b(N) MSB MSB φ2 φ2 1 1 φ1 φ1 φ3 φ3 I & Q DDFS/DAC 27 ma at 3V, 80 MHz φ2 φ2 CM CM + + Q-to-V Buffer Low-power through differetial implemetatio usig quasi-passive charge-redistributio pipelies Liearity limited by capacitace mismatch, voltagedepedet parasitics Glitch free! φ2

10 Measured DDFS/DAC Spectral Outputs 50 MHz Sample Rate 3 V Supply 50 MHz Sample Rate 3 V Supply MHz 62 db 57 db 0 5 MHz 0 25 MHz 57 dbc Spurious level as predicted set by capacitor mismatch Iter-cell capacitace causes o-liearity at high frequecy

11 Basebad Toe-Select Filter Trackig Hopped Local Oscillator RF I Low-Order Ati-alias Filter Fifth-Order Elliptic Lowpass Filter To Digital FSK Detector Dowcoverted Spectrum LPF Respose 13 MHz +13 MHz 13 MHz +13 MHz 5th-order Elliptic LPF with 200-kHz cutoff implemeted as SCF; dissipates 15 mw from 3- V at 5 MHz sample rate. Operates up to 20 MHz. 60 db stopbad atteuatio. LPF sets oise badwidth of etire system Frequecy, khz 1000

12 Lowpass Chael-Select Filter Dowcoverted Spectrum LPF Respose 13 MHz +13 MHz 13 MHz +13 MHz 26 MHz 915 MHz >40 db Dowcovert f RF /16 0dB 620 khz 50dB at 13 MHz 2d-Order Butterworth Prefilter f RF /64 24dB 230 khz 320 khz 6th-Order Elliptic Chael Filter 50 db LNA BQ1 Q = 0.65 Gai = 4 BQ2 Q = 8.1 Gai = 4 BQ3 Q = 1.9 Gai = 1

13 Measured Filter Performace 70 V/Hz i passbad 4.6 ma from 3V 200 pf total o-chip capacitace

14 Digital Toe Detector coswt (1b) I&D I&D A + B A + B Max Select MSB siwt (1b) I&D I&D A + B A + B MUX 9b 1-bit oversampled correlator (programmable oversample rate) Multipliers are switches, itegrators are accumulators 1.9 sq mm active area implemetatio will dissipate 2 mw

15 Ratioale Uderlyig UCLA Low-Power Trasceiver Radio pagig receiver is the most evolved low-eergy wireless device today. Receives 500 to 1000 b/s at 400 MHz to 900 MHz. Log battery life obtaied through very high level of itegratio (two chips) ad optimized system desig UCLA trasceiver uses this as a model. Key extesios are: Two-way commuicatio Much higher data rate 160 kb/s (programmable) Robust operatio i multipath eviromet Diversity Large multi-user capacity CDMA spread-spectrum Features Biary FSK modulatio of carrier (like pager) Frequecy-hopped spread-spectrum Simple demodulatio after de-hoppig (like pager) Two-chip trasceiver (like pagig receiver)

16 New Techology for Etchig Iductors Need fast etchat i p+ doped substrates Should miimally etch exposed metallizatio Xeo DiFluoride (XeF 2 ) gasphase etchat Etches hemispherical pits aisotropically through array of small holes i oxide Depth of etchig may be visually moitored through semi-trasparet itride

17 1 GHz Cotiuous-Time LNA ad Mixer A demostratio of the fudametal capability of MOSFETs to attai low oise ad wide dyamic rage, at low power 1-µm CMOS operatig at 3V; matched to 50W at iput Drai 8 ma from 3V VC M3 1000µm M10 960µm 50H 3µm RF I+ M1 300µm VG M2 RF I IF+ LO+ M6 LO 300µm M9 IF LO+ RF+ M4 80µm RF M5

18 LNA Desig Ratioale 2 Gai= Q R g = s m ( w C) R 50W R s F T ª H G I K J F H G I2 50W w K J s w0 Measured f T vs V GS -V t V GS -V t, V 50 H o-chip iductor load Rs db gai requires bias at (V GS V t )=0.6V for sufficietly high f T LNA + mixer drai 8 ma from 3 V

19 Chael-Select Filter LNA 2d-Order Butterworth Prefilter 6th-Order Elliptic Chael Filter 0.5dB >40 db 12dB 620 khz 54dB at 14 MHz 24dB 230 khz 320 khz 50 db 915 MHz Curret drai of active filter ~ 3.5 ma Iput-referred oise ~ 40 V/ Hz Capacitor spread = 108 Iput capacitor ~ 0.45 pf Output compressio poit ~ 2 V ptp

20 Icreasig DDFS/DAC Clock Frequecy 100Ω f2 f3 f3 f2 1 1 f5 f5 CM f4 CM µm ( + Elimiate two clock phases, f4 ad f5, i buffer drivig o-chip capacitive load Rescale DDFS. Carry-select adder i accumulator. Use ope-loop buffer to drive polyphase filter through four-fet switch upcoversio mixers 3rd-order distortio, icludig buffer < 45 db 600 µm 100 W

21 Polyphase Filter for Sidebad Selectio Q 600 W 0.3 pf ~270 ~180 I I ~0 ~90 Q Extesio of the RC-CR phase-shift etwork, with four-phase iputs ad outputs Reiforces oe sequece of quadrature phases (clockwise, say), while atteuatig the other Robust agaist compoet mismatches (orderof-magitude better tha sigle-phase etwork) Similarly selects oe sidebad after upcoversio (60 db rejectio with 10 phase error i LO) Image Desired O Hz 90 0 I Q LO Image LO LO + Desired

22 Trasmitter Test Chip mm active area 65 ma active curret

23 Trasmitter Output Spectra No off-chip filter at power amplifier output Measuremets at mid-rage level +5 dbm

24 Curret Drai i Trasceiver Parts ma 8 ma 8 ma 20 ma + 7 ma PD Filt VCO 7 ma ma 14 ma Limitig Amplifier Limitig Amplifier 2 ma Chael Filter Chael Filter 7 ma 15 ma

25 Measured Performace of Frot-Ed Frequecy, GHz