A new approach to the phase error and THD improvement in linear phase IIR filters

This paper deals with the real-time implementation of the IIR lters having linear phase. Powell and Chau have devised an e cient method for the design and realization of real-time linear phase IIR lters using suitable modi cations of the well-known time reversing technique. In their method, the input signal is divided into L-sample segments, time-reversed, and twice ltered using two IIR lter blocks whose transfer functions are the same. The performance has been further improved by Willson and Orchard, where double zeros on the unit circle have been separated, giving better amplitude response in the stop-band and slightly smaller amplitude and phase distortions. In this paper, new improvements are described based on the reordering of polynomials in the numerator of the lter transfer function, or on the appropriate selection of the transfer function. The truncation noise, phase and amplitude errors of new realizations show considerable improvement over the previous solutions.