Sharpened comb decimator with improved magnitude response

A new structure for the realization of a comb decimation filter with a sharpened magnitude response is advanced. The proposed structure consists of two main sections: a comb section and a sharpening comb section with the latter section operating at a lower rate than the high input rate. Using a polyphase decomposition, the sub-filters of the first section can also be operated at this lower rate. The improved magnitude response has been obtained by using the filter sharpening approach of J.F. Kaiser and R.W. Hamming (see IEEE Trans. on Acoustics, Speech, and Sig. Process., vol.ASSP25, p.415-22, 1977). The proposed filter has much less passband droop and better attenuation than the equivalent comb filter.