Linear phase equiripple IIR digital filter design

In this paper, a design approach for stable IIR digital filters with equiripple magnitude in passband and stopband and linear phase in passband is presented. The design approach adopts a constant group delay all-pole filter in the denominator and a mirror image polynomial transfer function in the numerator. Starting with a suitable filter order and a constant group delay value for the denominator, the Remez exchange algorithm is used to aid the design of the equiripple passband and stopband numerator transfer function. Equiripple passband and stopband characteristic offers benefits of reduced width in transition band and lower filter order. Lowpass, highpass, bandpass, and bandstop filter design examples are given.