A robust 3/sup rd/ order low-distortion multi-bit sigma-delta modulator with reduced number of op-amps for WCDMA

This paper describes a novel single-loop multi-bit (3 bits) sigma-delta modulator (SDM) with reduced number of operational amplifiers for wideband WCDMA. Such an architecture is based on a simplified analog structure that not only features low distortion but also provides an aggressive and significantly enlarged noise shaping bandwidth with low oversampling ratio (OSR). With a sampling frequency of 39 MHz and an OSR of 10 the proposed circuit can achieve 74 dB SFDR.