FIR filters using interpolated prefilters and equalizers

Novel digital FIR (finite-impulse-response) prefilter structures with periodic impulse response are introduced. The prefilter consists of an interpolated recursive running sum coupled to a nonrecursive structure. By appropriately cascading these prefilters, large stopband attenuation can be obtained, relieving the task of the equalizer. A systematic design procedure for the cascade of prefilters and the equalizer is given, leading to computationally efficient FIR filters. The procedure is based on combining the prefilter-equalizer concepts of J.W. Adams and A.N. Wilson, Jr. (1983) with the IFIR (interpolated FIR) concepts of Y. Neuvo et al. (1987). Design examples are included, demonstrating that the proposed design procedure leads to significant savings in the number of arithmetic operations as compared to recently proposed designs