A Multirate Sigma Delta Modulator for Multi-standard Wireless Radio Receivers

A reconfigurable switched-capacitor (SC) sigma delta modulator topology intended for multi-mode zero-IF receivers has been presented on the system level. The modulator is based on the cascade of a single-bit 2-1-1 topology. The loop order and oversampling ratio are reconfigurable to meet the requirements of a wide range of standards. The multirate technique is introduced in the modulator to reduce the frequency of the first stage integrators of the cascade sima delta modulator. The power consumption of the modulator is decreased because the first stage integrators in the chain primarily determine the power dissipation of the whole modulator. A peak SNR of 85/ 81/ 65/ 63/ 56/ 46 dB is achieved for GSM/ Bluetooth/ GPS / WCDMA/ WLAN/ WiMAX mode. The simulation results show that the proposed topology obtains similar performances to the conventional cascade modulator structure for the multi-mode receivers, while the speed requirements of the operational amplifiers in the first stage is relaxed.