Perfect linear phase IIR filter with flat passband amplitude and equiripple stopband attenuation characteristics

Abstract

SUMMARYIt is known that several techniques for real-time implementation of perfect linear phase IIR filters have been developed, achieving higher computational efficiency than conventional FIR filters with similar performance. This paper presents new methods for designing transfer function of perfect linear phase IIR filters with flat passband and equiripple stopband amplitude characteristics. The proposed methods are based on the formulation of an eigenvalue problem for low-pass filters and a set of linear equations for bandpass filters. In wide-band, narrow transition cases, a bump in amplitude may appear near the band edge. However, it can be removed by specifying amplitude to unity at several frequencies. The methods are computationally efficient. Design examples of low-pass and bandpass filters are shown.