Design of IIR multi-band filters using IIR all-pass eigenfilters

An efficient method is proposed to design infinite impulse response (IIR) all-pass filters for synthesizing general multiband filters of low sensitivity. The method is based on minimizing a quadratic measure of the error derived from the phase design of a certain filter. The problem of stability is of no concern, and the performance of the obtained filter is comparable to that of existing methods. The solution is obtained directly with no need for iteration. The complex coefficient filters can also be designed with minor modification of the proposed method