가변 널 주파수를 가진 재구성 가능한 공간상 이산시간 이동평균 필터

A non-decimation 2 nd 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. By decimation operation, the aliasing problem can be avoided. The filter is designed with variable weight of coefficients as 1:α:1 where α varies from 1 to 2. This corresponds to the change of null frequencies within the range of fS/3~fS/2 and fS/2~2fS/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 0.38~0.49fS and 0.51~0.62fS.