A dual-mode low-distortion sigma-delta modulator with relaxing comparator accuracy

A dual-mode single-loop multibit (3 bits) sigma-delta modulator (SDM) with reduced number of op-amps is proposed for satisfying the GSM/WCDMA standard. Such architecture is based in a simplified analog structure that not only features low distortion but also provides an aggressive and significantly enlarged noise shaping bandwidth with low over-sampling ratio (OSR). In addition, the resolution of comparators in the quantizer is relaxed to reduce the power consumption. Simulations in system- and transistor-level simulations prove a dynamic range of 88dB & 60dB in GSM & WCDMA respectively.