Allpass filter design and applications

The problem of allpass lter design for phase approximation and equalization in the Chebyshev sense is solved by using a generalized Remez algorithm. Convergence to the unique optimum is guaranteed and is achieved rapidly in the actual implementation. The well-known numerical problems for higher degree lters are analyzed and solved by a simple approach. Possible applications are: design of lters with a desired phase response (e.g., a delay element), the design of phase equalizers, or the design of recursive lters with magnitude prescriptions using parallel allpass lters. For the latter the algorithm can be modiied to allow arbitrary tolerance schemes for the magnitude response.