A low-voltage single-Opamp 4th-order band-pass /spl Delta//spl Sigma/-modulator

A band-pass /spl Delta//spl Sigma/-modulator can be used to directly digitize the IF signal in a radio receiver. As the resolution and the channel bandwidth of a band-pass /spl Delta//spl Sigma/-modulator can easily be traded afterwards, it is the key circuit block in implementing receivers for future multi-mode mobile phones. However, the reported implementations have been based on resonator structures which are poorly suited to a low supply voltage which has led to high power consumptions. A switched-capacitor double-delay resonator structure which imposes no limitation on the Opamp output scaling is proposed. The structure allows the optimization of Opamp output swings with no power penalty and is thus ideally suited for low supply voltage. A single Opamp bandpass /spl Delta//spl Sigma/-modulator which shares the Opamp between two double-delay resonators is presented along with behavioral level simulation results. According to the simulations the presented BP /spl Delta//spl Sigma/-modulator achieves 14 b-resolution for the GSM-channel bandwidth (BW=270 kHz) and 6 b-resolution for the WCDMA-channel bandwidth (BW=3.84 MHz).

[1]  W. M. Snelgrove,et al.  A 160-MHz fourth-order double-sampled SC bandpass sigma-delta modulator , 1998 .

[2]  L. Longo,et al.  A 15 b 30 kHz bandpass sigma-delta modulator , 1993, 1993 IEEE International Solid-State Circuits Conference Digest of Technical Papers.

[3]  A. Hairapetian,et al.  An 81 MHz IF receiver in CMOS , 1996, 1996 IEEE International Solid-State Circuits Conference. Digest of TEchnical Papers, ISSCC.

[4]  Shen-Iuan Liu,et al.  A double-sampling pseudo-two-path bandpass /spl Delta//spl Sigma/ modulator , 2000, IEEE Journal of Solid-State Circuits.

[5]  B.A. Wooley,et al.  A two-path bandpass /spl Sigma//spl Delta/ modulator for digital IF extraction at 20 MHz , 1997, 1997 IEEE International Solids-State Circuits Conference. Digest of Technical Papers.

[6]  K. Halonen,et al.  A 2.7V CMOS dual-mode baseband filter for PDC and WCDMA , 2000, Proceedings of the 26th European Solid-State Circuits Conference.

[7]  William Martin Snelgrove,et al.  Switched-capacitor bandpass delta-sigma A/D modulation at 10.7 MHz , 1995, IEEE J. Solid State Circuits.

[8]  Bang-Sup Song,et al.  A fourth-order bandpass delta-sigma modulator with reduced numbers of op amps , 1995 .

[9]  L. Longo.  A 15b 30kHz bandpass sigma-delta modulator , 1993 .

[10]  Bruce A. Wooley,et al.  FP 13.3: A Two-Path Bandpass XA Modulator for Digital IF Extraction at 20MHz* , 1997 .