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Improved sharpening of comb-based decimation filters: Analysis and design

In this work, we propose a new method to design sharpened comb filters to attain given specifications on the acceptable maximum passband distortion as well as on selec-tivity. The key idea hinges upon the definition of a sharpening polynomial with as many coefficients as the number of constraints imposed. The sharpening filter design is then optimized through a Particle Swarm Optimization algorithm in order to find power-of-2 coefficients for the sharpening polynomial so as to desig a multiplierless decimation filter. A design example is discussed in order to contrast the magnitude responses of the proposed filters among each other, to show the improved performance in terms of passband distortion and selectivity with respect to classical comb filter, and to highlight the key design steps of the proposed design.