Design of Equiripple Minimum Phase FIR Filters with Ripple Ratio Control

Masahiro OKUDA

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E89-A    No.3    pp.751-756
Publication Date: 2006/03/01
Online ISSN: 1745-1337
DOI: 10.1093/ietfec/e89-a.3.751
Print ISSN: 0916-8508
Type of Manuscript: PAPER
Category: Digital Signal Processing
FIR filter,  minimum phase,  ripple ratio,  bandpass filters,  

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In this paper, we present a numerical method for the equiripple approximation of minimum phase FIR digital filters. Many methods have been proposed for the design of such filters. Many of them first design a linear phase filter whose length is twice as long, and then factorize the filter to obtain the minimum phase. Although these methods theoretically guarantee its optimality, it is difficult to control the ratio of ripples between different bands. In the conventional lowpass filter design, for example, when different weights are given for its passband and stopband, one needs to iteratively design the filter by trial and error to achieve the ratio of the weights exactly. To address this problem, we modifies well-known Parks-McClellan algorithm and make it possible to directly control the ripple ratios. The method iteratively solves a set of linear equations with controlling the ratio of ripples. Using this method, the equiripple solutions are obtained quickly.