A Quadrature Bandpass Continuous-Time Delta-Sigma Modulator for a Tri-Mode GSM-EDGE/UMTS/DVB-T Receiver

A second-order multi-bit quadrature bandpass continuous-time delta-sigma modulator (QBP-CTDSM) employing a power-scaling technique (PST) and a quadrature mismatch scrambler (QMS) for a tri-mode GSM-EDGE/UMTS/DVB-T low-IF receiver is reported in this paper. This modulator employs operational amplifiers with PST to optimize power consumption among the tri-mode operation. In addition, the modulator incorporates the proposed QMS to mitigate the mismatch between the I/Q multi-bit DACs. Fabricated in a 0.18-μm CMOS process, the proposed QBP-CTDSM achieves 81/61.2/60.9 dB SNDR across 270- kHz/5-MHz/8-MHz bandwidth. The bandpass center frequency is programmable from 500 kHz to 12 MHz. Measured from a 1.8-V supply voltage, the modulator power consumptions are 4.9/8.9/12.1 mW for the GSM-EDGE/UMTS/DVB-T modes, respectively, which result in FOMs of 0.99/0.95/0.84 pJ/conversion. The measurement results also show that the QBP-CTDSM achieves image rejection ratios better than 55 dB for all modes.