Design of Quasi-Equiripple IIR Filters with Prescribed Flatness and Approximately Linear Phase

Yasunori Sugita

Keywords

IIR filter, Flat magnitude, Flat group delay, Equiripple characteristics, Quadratic programming

Abstract

In this paper, we propose a method for designing quasi-equiripple infinite impulse response (IIR) filters with prescribed flatness and approximately linear phase characteristics. In the proposed method, the flatness condition in stopband is preincorporated into the transfer function and the design problems are formulated as an iterative quadratic programming (QP) problem. The flatness condition in passband is added to the QP problem as the linear matrix equality. As a result, the proposed method can design the IIR filters which have an equiripple response and prescribed flatness in passband or stopband or both. Finally, we show some design examples and confirm the effectiveness of the proposed method.

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