Recursive quadrature mirror filters--Criteria specification and design method

Criteria are found for a pair of recursive infinite impluse response (IIR) filters which have mirror image amplitude responses and whose outputs are in phase quadrature at all frequencies. A method is suggested for designing filters with these characteristics, and their performance and processing requirements are compared with a typical nonrecursive finite impluse response (FIR) realization. A particular filter is described in more detail, and it is shown how it could be incorporated in a multiband processing scheme. It is concluded that recursive quadrature mirror filters could offer considerable savings in terms of signal processing compared with nonrecursive filters with similar performances. Additionally, it is suggested that, because they can be designed to have relatively short absolute delays, the performance of the IIR filters may prove superior for certain applications.