A reconfigurable spatial moving average filter in sampler-based discrete-time receiver

A non-decimation second-order spatial moving average (SMA) discrete-time (DT) filter is proposed with reconfigurable null frequencies. The filter coefficients are changeable, and it can be controlled by switching sampling capacitors. So, interferers can be rejected effectively by flexible nulls. Since it operates without decimation, it does not change the sample rate and aliasing problem can be avoided. The filter is designed with variable weight of coefficients as 1:α:1 where a varies from 1 to 2. This corresponds to the change of null frequencies within the range of f_s/3~f_s/2 and f_s/2~2f_s/3. The proposed filter is implemented in the TSMC 0.18-μm CMOS process. Simulation shows that null frequencies are changeable in the range of 0.38~0.49 f_s and 0.51~0.62f_s.