FRACTIONAL DELAY FILTER DESIGN WHEN SAMPLING RATE HIGHER THAN NYQUISTRATE

Fractional delay filter design is used to approximate the delay filter exp(-j omega D) with a delay D for the full band \omega\ < pi, using E-IR filters or IIR allpass filters. The author shows that the fractio nal delay filter design is necessary only when sampling is critical, i .e. Nyquist sampling. It is shown that, when the sampling rate is high er than the Nyquist rate, the ideal delay filter exp(-j omega D) for t he baseband \omega\ < pi/r only needs to be approximated, where r is t he ratio of sampling rate over the Nyquist rate. Numerical simulations are presented to illustrate the theory.