A 70-MHz continuous-time CMOS band-pass Sigma Delta modulator for GSM receivers
A 70-MHz continuous-time CMOS band-pass SigmaDelta modulator for GSM receivers is presented. Impulse-invariant-transformation is used to transform a discrete-time loop-filter transfer function into continuous-time. The continuous-time loop-filter is implemented using a transconductor-capacitor (G(m)-C) filter. A latched-type comparator and a true-single-phase-clock (TSPC) D flip-flop are used as the quantizer of the SigmaDelta modulator. Implemented in a MOSIS HP 0.5-mum CMOS technology, the chip area is 857 mum x 420 mum, and the total power consumption is 39 mW. At a supply voltage of 2.5 V, the maximum SNDR is measured to be 42 dB, which corresponds to a resolution of 7 bits.
gsm receivers band-pass sigma-delta modulator analog-to-digital converter continuous-time filters