Pre- and postfiltering effects on SCF stopband attenuation

The switched capacitor filter (SCF) design procedure for the case when the oversampling ratio of the sampling frequency to the cutoff frequency is not much greater than 1 is proposed. The resulting filter yields a larger stopband attenuation than that traditional elliptic filter, and it compensates for the effect of the undesirable zero-order sample-and-hold. The design procedure increases the requirement of wideband signal processing, and it helps to design filters with low oversampling rates. Though the all-pole Butterworth-type transfer functions are used, the Chebyshev type or elliptic filter can be designed with little modification of the proposed procedure