A 1.55 GHz to 2.45 GHz Center Frequency Continuous-Time Bandpass Delta-Sigma Modulator for Frequency Agile Transmitters

Transcription

1 RMO2C A 1.55 GHz to 2.45 GHz Center Frequency Continuous-Time Bandpass Delta-Sigma Modulator for Frequency Agile Transmitters RFIC 2009 Martin Schmidt, Markus Grözing, Stefan Heck, Ingo Dettmann, Manfred Berroth Institute of Electrical and Optical Communications Engineering Stuttgart, Germany Dirk Wiegner, Wolfgang Templ Alcatel-Lucent, Bell Labs Stuttgart Stuttgart, Germany 1

2 Outline Motivation Class-S Transmitter CT BPDSM Design System Architecture Key Components Experimental Results Die Photo Single-Tone Measurements UMTS Measurements Measurement Summary Conclusion 2

3 3GPP Evolution and Effect on RF Transmitters Standard Channel Typical access crest factor of method clipped signal GSM TDM/FDM 0 db UMTS CDMA FDD 6 db CDMA450 CDMA 6 db LTE OFDMA >6 db 3

4 3GPP Evolution and Effect on RF Transmitters Standard Channel Typical access crest factor of method clipped signal GSM TDM/FDM 0 db UMTS CDMA FDD 6 db CDMA450 CDMA 6 db LTE OFDMA >6 db In future: Higher-order constellations More code channels/subcarriers at the same time for CDMA/OFDMA Transmission on several carriers at the same time High peak-to-average-power-ratio Low power efficiency for conventional architectures 3

5 3GPP Evolution and Effect on RF Transmitters Standard Channel Typical Carrier access crest factor of frequency method clipped signal (downlink) GSM TDM/FDM 0 db 900 MHz,1.8 GHz UMTS CDMA FDD 6 db 2.14 GHz,... CDMA450 CDMA 6 db 450 MHz LTE OFDMA >6 db 900 MHz, 1.8 GHz, 2.1 GHz, 2.6 GHz In future: Higher-order constellations More code channels/subcarriers at the same time for CDMA/OFDMA Transmission on several carriers at the same time High peak-to-average-power-ratio Low power efficiency for conventional architectures Many coexisting standards Refarming of frequency bands Need for a multi-band, multi-standard transmitter 3

6 Class-S Transmitter Conventional RF Transmitter Digital baseband processor LO 0 90 PA Filter + PA RF 4

7 Class-S Transmitter Conventional RF Transmitter Digital baseband processor LO 0 90 PA Filter + PA RF 4

8 Class-S Transmitter Conventional RF Transmitter Digital baseband processor LO 0 90 PA Filter + PA RF Class S Transmitter Digital baseband processor LO 0 90 CT BPDSM PA RF 4

9 Class-S Transmitter Conventional RF Transmitter Digital baseband processor LO 0 90 PA Filter + PA RF Class S Transmitter Digital baseband processor LO 0 90 CT BPDSM PA Digital control RF 4

10 Class-S Transmitter: Signal Waveforms Time Domain BPDSM Power Amplifier Frequency Domain 5

11 CT BPDSM Design 6

12 System Architecture E(z) X(z) z 2 z 2 Y(z) k 2h k 2r k 1h k 1r G 1r (z) G 1h (z) G 2r (z) G 2h (z) 1 Design of transfer function in discrete-time domain 7

13 System Architecture E(z) X(z) z 2 z 2 Y(z) k 2h k 2r k 1h k 1r G 1r (z) G 1h (z) G 2r (z) G 2h (z) 1 Design of transfer function in discrete-time domain 2 Impulse-invariant transform continuous-time modulator 7

14 System Architecture G q G q Analog RF input G m LC G m LC Preamp Latch Latch Latch Latch Output bitstream k 1r A D RZ Latch k 1h A D RZ Latch Latch k 2r A D RZ Latch k 2h A D RZ Latch Latch 1 Design of transfer function in discrete-time domain 2 Impulse-invariant transform continuous-time modulator 3 Multi-feedback design simplifies filter construction 7

15 System Architecture 1 Design of transfer function in discrete-time domain 2 Impulse-invariant transform continuous-time modulator 3 Multi-feedback design simplifies filter construction 4 30 bit register: Center frequency and input power configurable 7

16 Key Components 5 Configuration Register G q G q Analog RF input G m LC G m LC Preamp Latch Latch Latch Latch Output bitstream k 1r A D RZ Latch k 1h A D RZ Latch Latch k 2r A D RZ Latch k 2h A D RZ Latch Latch 1 Configurable transconductance 8

17 Key Components 5 Configuration Register G q G q Analog RF input G m LC G m LC Preamp Latch Latch Latch Latch Output bitstream k 1r A D RZ Latch k 1h A D RZ Latch Latch k 2r A D RZ Latch k 2h A D RZ Latch Latch 1 Configurable transconductance 2 Configurable Q-enhanced resonator 8

18 Configurable Transconductance Amplifier (TCA) out out+ in+ in 2R e I 0 /2 I 0 /2 V b (1) VEE 1 Shunt emitter degeneration works with low supply voltages 9

19 Configurable Transconductance Amplifier (TCA) out out+ out out+ in+ in in+ in 2R e I 0 /2 I 0 /2 V b R e V b I 0 R e (1) VEE (2) VEE 1 Shunt emitter degeneration works with low supply voltages 2 Series emitter degeneration exhibits 4.6 db less noise power than shunt emitter degeneration: chosen for this design 9

20 Configurable Transconductance Amplifier (TCA) (3) 1 Shunt emitter degeneration works with low supply voltages 2 Series emitter degeneration exhibits 4.6 db less noise power than shunt emitter degeneration: chosen for this design 3 5 binary weighted TCAs are used for G m and G q 9

21 Configurable Q-enhanced Resonator VCC in+ V varac G q in VCC 10

22 Differential Switchable Capacitance in+ in 11

23 Differential Switchable Capacitance in+ virtual in virtual in+ in 11

24 Differential Switchable Capacitance in+ virtual in in+ I ctrl virtual in in 11

25 Differential Switchable Capacitance in+ in+ in virtual in virtual in+ I ctrl virtual in+ virtual in in 11

26 Configurable Capacitance with Binary Weighted Coefficients 12

27 Experimental Results 13

28 Die Photo 14

29 Die Photo: Active Resonator G m C switch LC-Resonator G q Feedback DAC 15

30 Die Photo: Overall Structure Active Resonator Register and Comparator and and Feedback Current Switches 50Ω Driver 16

31 Output Spectrum (0 GHz GHz) for f c = 2.2 GHz Output power [dbm] Frequency [GHz] 17

32 Output Power and Noise Floor in 20 MHz BW for f c = 2.2 GHz 0 1 db compression point 10 Output power [dbm] Pout Pnoise peak SNR Input power [dbm] 18

33 Signal-to-Noise-Ratio for f c = 1.55GHz GHz Power [dbm] Pout SNR in = P 1 db 1dB SNR peak (2.2GHz) = 45.5dB SNR peak (1.55GHz) = 40.7dB 40 Pnoise Frequency [GHz] 19

34 ACLR for Unclipped UMTS FDD Downlink Signal at f c = 2.2 GHz 30 Output power [dbm] f center = 2.2GHz Crest Factor = 10.5 db (10 codes@30 kbps) ACLR(±5MHz) = 42.8 db ACLR(±10MHz) = 43.5 db Frequency [GHz] 20

35 Summary Measurement results Center frequency 1.55 GHz GHz Sampling frequency 7.5 GHz Peak SNR in 20 MHz BW 45.5 db Power consumption 992 mw W Chip area 2.2 mm 2 UMTS This work (CF=10.5 db) requirements ACLR 5 MHz 45 db 42.8 MHz 50 db 43.5 db ACLR 5 MHz 33 db 48.4 MHz 43 db 49 db Range where Composite EVM<12.5% (for 16QAM) 24 db 21

36 Conclusion Design of a CT BPDSM was described 22

37 Conclusion Design of a CT BPDSM was described Key components were presented: Configurable low noise transconductor Q-enhanced resonator Configurable resonator capacitance 22

38 Conclusion Design of a CT BPDSM was described Key components were presented: Configurable low noise transconductor Q-enhanced resonator Configurable resonator capacitance Measurements: Signal frequency range 1.55 GHz GHz SNR 45.5 db in 20 MHz bandwidth UMTS: ACLR for unclipped downlink channel not far away UMTS: EVM for 16QAM sufficient over 24 db power range 22

39 Thank you for your attention 23

40 Results: Comparison with State of the Art Ref Technology f signal f clock SNR BW SNR Power [GHz] [GHz] [db] [MHz] [db] [mw] [A] SiGe [B] BiCMOS [C] BiCMOS This work SiGe *normalized to a bandwidth of 1 MHz. [A] Weinan Gao; Cherry, J.A.; Snelgrove, W.M., A 4 GHz fourth-order SiGe HBT band pass Σ modulator, VLSI Circuits, Digest of Technical Papers Symposium on, vol., no., pp , Jun 1998 [B] Chalvatzis, T.; Gagnon, E.; Repeta, M.; Voinigescu, S.P., A Low-Noise 40-GS/s Continuous-Time Bandpass Σ ADC Centered at 2 GHz for Direct Sampling Receivers, Solid-State Circuits, IEEE Journal of, vol.42, no.5, pp , May 2007 [C] Thandri, B. K.; Silva-Martinez, J., A 63 db SNR, 75-mW Bandpass RF Σ ADC at 950 MHz Using 3.8-GHz Clock in 0.25-µm SiGe BiCMOS Technology, Solid-State Circuits, IEEE Journal of, vol.42, no.2, pp , Feb

41 Composite EVM versus Input Power for f c = 2.2 GHz Composite EVM [%] Input power [dbm] 25