A 28mW Spectrum-Sensing Reconfigurable 20MHz 72dB-SNR 70dB-SNDR DT ΔΣ ADC for 802.11n/WiMAX Receivers

A reconfigurable power-adaptive DT DeltaSigma ADC for intelligent 802.11n/WiMAX receivers (20 to 2.5MHz per I/Q) is presented. The intent is to replace complex analog baseband circuits with a combination of tunable one-pole filter, anti-alias filter and coarse VGA in Paramesh, J. et al (2006). Blocker filtering, fine variable-gain amplification and variable-BW channel selection are moved to the digital baseband. The SNR is optimized as a function of signal and out-of-band blocker power in Behbahani, F. et al, (2001) by reconfiguring the modulator order into one of 4 modes at constant fs, thereby keeping anti-aliasing unchanged. A 5b flash ADC integrated in the converter is the front end of a simple spectrum analyzer (SSA). Spectrum sensing and reconfigurability are accomplished without compromising ADC performance.