Improving Magnitude Response of Comb Two-Stage Structure Using Simple Multiplierless Filters

Abstract

This paper presents novel two-stage comb-based decimation structure for even decimation factors. First stage and second stages are decimated by $M/2$ and 2, respectively, where $M$ is the decimation factor. In the second stage is the cascade of multiplierless corrector filter and sharpened cascade of the corrector and comb. Filters in second stage improve magnitude characteristic of comb in odd folding bands and decrease comb passband droop. In the first stage is the cascade of comb and multiplierless modified filter. This modified filter improves alias rejection not only in even folding bands, but also in odd folding bands. Method is illustrated with two examples and the corresponding structure is presented. Finally, the method is compared with similar methods in literature.