A non-uniform resolution step GHz 7-bit flash A/D converter for wideband OFDM signal conversion

A 1 GHz 7-bits flash A/D converter is fabricated in 90 nm CMOS technology to be used as part of an analog front end (AFE) for digitising of OFDM communication signals. To extend the receiver bandwidth, input capacitance-reducing techniques are used. The motivation in implementing a non-uniform resolution step and the challenges in its physical implementation are discussed. To further reduce the input capacitance, small geometries are used in the comparator input pair, where the offset is corrected by a number of calibration strategies. The converter achieves extended resolution and SNR, and input bandwidth compared to conventional architectures.