Minimax design of multiplierless sharpened CIC filters based on interval analysis

Abstract

Polynomial sharpening of amplitude responses of cascaded-integrator-comb (CIC) filters is often used to improve folding-band attenuations. The design of sharpened CIC (SCIC) filters is based on searching the polynomial coefficients ensuring required magnitude response. Several design methods have been developed, resulting in real, integer, and sum-of-powers-of-two (SPT) coefficients. The latter are preferable since they result in multiplierless structures. In this paper, we present a method for the design of SCIC filters with SPT polynomial coefficients by using the minimax error criterion in folding bands. To obtain the coefficients, we use a global optimization technique based on the interval analysis. The features of the presented method are illustrated with the design of wideband SCIC filters.