Design of sharp-cutoff FIR digital filters with prescribed constantgroup delay

摘要

This paper addresses the design problem of sharp-cutoff FIRnfilters with prescribed constant group delay. The frequency-responsenmasking (FRM) approach for designing sharp linear-phase (SLP) FIRnfilters is generalized to solve the design problem. The optimalninterpolation factor M required in the FRM structure is determined bynminimizing a proposed complexity measure of the designed sharp-cutoffnFIR filter. Then the bandedge frequencies associated with each subfilternof the FRM structure can be determined. A method is proposed to find thencorresponding group delay for each subfilter by solving a set of linearnequations derived from the selected M and the prescribed constant groupndelay. After finding the required design specifications, we present anmethod based on a weighted least squares (WLS) algorithm for the minimaxndesign of each subfilter. Finally, a modified discrete optimizationnprocedure in conjunction with the WLS algorithm is proposed forndesigning sharp-cutoff FIR filters with powers-of-two coefficients asnwell as constant group delay. Several design examples are given fornillustration