A Reconfigurable Double Sampling Sigma Delta Modulator for 4G Wireless Receivers

Abstract

A reconfigurable cascade sigma delta modulator with single-bit quantizers for multi-mode zero-IF receivers has been presented on the system level. The modulator was based on single-bit quantizers and utilized feed-forward path to increase the dynamic range. The double-sampling technique was adopted to improve the over-sampling ratio (OSR) over a wide bandwidth range. The loop order and OSR were reconfigurable to meet the requirements of a wide range of standards. The coefficient scaling was deduced to obtain the desired noise shaping. The effects of circuit non-idealities on the modulator performance were modeled and analyzed in MATLAB/ SIMULINK to extract the required circuit parameters. A peak SNDR of 85/ 85/ 67/ 65/ 57/ 48 dB is achieved over a 0.2/ 1/ 2/ 3.84/ 22/ 28 MHz channel bandwidth at a sampling frequency of 25.6/ 128/ 48/ 84.5/ 264/ 280 MHz for GSM/ Bluetooth/ GPS / WCDMA/ WLAN/ WiMAX mode. The proposed modulator fulfills the performance requirements of 4G mobile communication standards.