Design of FIR digital filters with novel prefilter structures

Abstract

Two novel prefilter structures, the cascade of cosine functions (CCOSs) and a bandpass function derived by the cascade of cosine functions (BPC), are discussed. The CCOSs and BPCs are FIR functions. The implementation of CCOSs requires no multipliers and few additions, and the implementation of BPCs requires two multipliers and few additions. These prefilters can be combined with an appropriately designed equalizer based on equiripple methods, leading to an efficient FIR digital filter design. Some efficient prefilter structures derived by Adams and Willson using a combination of RRSs and CCOSs are also discussed. The number of multipliers required to implement the prefilter-equaiizer cascade with the prefilter proposed in this paper can be reduced to nearly 35% of that designed by the direct-form minimax method of McClellan and Parks. The BPC is efficient for the design of bandpass filters. By using this function as a prefilter, the number of multipliers of the corresponding equalizer required to satisfy...