Sharpening of partially non-recursive CIC decimation filters

The cascaded integrator comb filter is commonly used as a first stage decimation filter in communications systems. This paper reviews sharpening techniques for correcting the passband 'droop' present in the frequency response of these filters. A variation on an existing technique that would allow a partially non-recursive (and, therefore, potentially higher speed) implementation is presented for CIC filters with power of two decimation ratios.