A 3mW continuous-time /spl Sigma//spl Delta/-modulator for EDGE/GSM with high adjacent channel tolerance

A continuous-time 4th-order multi-bit /spl Sigma//spl Delta/-modulator for GSM/EDGE is presented. By introduction of a direct feed-forward path from the input to the quantiser, high immunity to adjacent channel interferers is achieved. The dynamic range is 90 dB (>14-bit) over a 240 kHz signal bandwidth. Accurate modelling allows optimisation of excess loop delay, thus yielding a very low power consumption of 3 mW at 1.25 V supply voltage. The modulator is clocked at 26 MHz (oversampling ratio=54). It occupies 0.5 mm/sup 2/ in a 0.13 /spl mu/m CMOS technology.