A method for the design of phase equalizers

A new method for the design of all-pass filters with arbitrary group delay characteristics is presented. Given the desired group delay, the magnitude of the corresponding minimum phase filter is found. The problem is then reduced to that of approximating a magnitude response by a stable all-pole filter or by a Finite-duration Impulse Response (FIR) filter with all its zeros outside the unit circle. It is shown with several examples that the resulting errors can present an almost equal ripple behavior. Comparisons with optimum Lpdesigns are made.