Design of multiplierless CIC compensators based on maximum passband deviation

Abstract

Cascaded-integrator-comb (CIC) decimation filters are the simplest multiplierless filters supporting high sample rate conversion factors. However, the magnitude response of high order CIC filters exhibits a high passband droop. Such a droop can be reduced by connecting an FIR compensator in the cascade with the CIC filter. In this paper, we present a method for the design of CIC compensators whose coefficients are expressed as a sum of powers of two (SPT). The method is based on the minimization of the difference between the maximum and the minimum passband amplitude. To obtain the compensator coefficients, we use a global optimization technique, which is based on the interval analysis. In the optimization, the number of SPT terms for each coefficient is specified. The compensators obtained efficiently compensate narrow and wide passbands by using three and five coefficients having small number of SPT terms. For these compensators, multiplierless structures are provided.