Programmable switched capacitor 4-tap FIR filter

A programmable fully differential switched capacitor 4-tap FIR filter is presented. The filter has fixed tap weights of 1,2,2,1 and programmable sample timing with maximum impulse response length of 6.75 t/sub clk/. One possible use is as a part of WCDMA receiver channel filter relaxing the strict LP filter requirements imposed by the WCDMA specifications regarding adjacent channel attenuation. The filter achieved a SNR of 73 dB, IM2 below-74 dBc and IM3 below -78 dBc for a 2Vpp full-scale differential sine input. The circuit was fabricated on a 0.35 /spl mu/m n-well CMOS process and operates at 2.8V with total current consumption of 3.5mA.