Comb-Cosine prefilter based decimation filter

This paper presents a new multistage Comb-Cosine decimation filter with an improved magnitude response. The passband droop of the comb filter is decreased by using a simple 2M order compensation filter. Using multirate identity this filter can be moved to the low rate becoming a second order filter. Additionally, the attenuation in the folding bands is increased using cosine prefilters, which can also be moved to a lower rate. The first section is realized in nonrecursive form. Using the polyphase decomposition, the subfilters of the first section can be operated at a lower rate, which depends on the down-sampling factor of the first section. The resulting structure is multiplierless and does not have any filtering at the high input rate.