A novel low-voltage 2/sup nd/-order sigma-delta modulator with double-sampling for GSM/DECT/WCDMA

This paper presents the design of a double-sampling multilevel sigma-delta modulator (SDM), with relaxed operational amplifier requirements, for GSM/DECT/WCDMA communication standards. The modulator operates with 1.8 V voltage supply (with chopper stabilization technique) and has been implemented in 0.35 /spl mu/m CMOS. A novel dynamic element matching (DEM) technique is introduced for a double-sampling SDM. The moving sum effect resulting from the fully floating switched-capacitor integrator in the feedback path has been reduced in order that the noise shaping performance remains unchanged in the signal band. The achieved SNR are 88 dB/70 dB/55 dB for GSM/DECT/WCDMA, respectively.