Design of narrow band filters using sampling rate alterations

A simple time domain analysis method is described for the design of wave digital filters capable of performing sampling rate alterations, with the case of a digital interpolator taken as an example. The method has been successfully used in the design of very narrow selective bandpass filters with bandwidths of 0.3% with the next spurious at 11 times the centre frequency, where standard frequency domain approaches fail to yield the correct results on a medium PC due to memory limitations.