A new method for designing allpass filters with equiripple group delay errors

Allpass filters have found many applications in signal processing areas. This paper describes an algorithm for the design of stable allpass digital filter with equiripple group delay errors. The problem is formulated as an iterative reweighted linear program (LP) problem. An algorithm is derived for solving such a problem. The design examples are given, which demonstrate that the proposed algorithm is very efficient and converges much faster than the existing ones for the design of allpass filters with equiripple constant group delay errors.