Current-Mode, WCDMA Channel Filter With In-Band Noise Shaping

A novel class of filters (called pipe filters) that features in-band noise reduction is presented and a current mode biquad cell based on cross-connected cascoded devices is introduced. The presented solution gives in-band high-pass noise shaping and passive pre-filtering of out-of-band blockers. This results in both low in-band noise and high out-of-band IIP3. A 4th-order lowpass prototype in 90 nm CMOS for WCDMA application features 32 μW in-band noise (when integrated over the 2 MHz bandwidth as defined by the standard) and +36 dBm out-of-band IIP3 which results in a 75 dB SFDR with 1.25 mW power consumption. Active die area is 0.5 mm².