Wideband low-distortion sigma-delta ADC for WLAN with rns based decimation filter

This work presents a wideband low-distortion sigma-delta analog-to-digital converter (ADC) with residue number system (RNS) based decimation filter for wireless local area network (WLAN) standard. The proposed converter makes use of low-distortion swing suppression SDM architecture which is highly suitable for low oversampling ratios to attain high linearity over a wide bandwidth. The modulator employs a 2-2 cascaded sigma-delta modulator with feed forward path with a single-bit quantizer in the first stage and 4-bit in the second stage. The modulator is designed in TSMC 0.18 um CMOS technology and operates at 1.8 V supply voltage. Simulation results show that, a peak SNDR of 57 dB and a spurious free dynamic range (SFDR) of 66 dB is obtained for a 10 MHz signal bandwidth, and an oversampling ratio of 8. The decimation filter downconverts the ADC output to the Nyquist rate. The proposed RNS based finite impulse response (FIR) filter provides high data rate operations due to fast multiply and accumulate operations in RNS domain.