A general design of mixed IIR-FIR two channel QMF bank

A general family of mixed IIR/FIR two-channel QMF filter banks with near perfect reconstruction (NPR) is presented. The design method is general in the sense that all possible distortions (aliasing, imaging, amplitude and phase distorsions) can be simultaneously and arbitrarily minimized. The method is based on a simple algorithm, also included, to approximate unstable all-pole filters with FIR filters. The resulting filter bank is efficient because a polyphase implementation is possible and delay is low compared to conventional FIR filter banks. It is also shown that some well-known two-channel FIR and IIR filter banks are particular classes of the proposed one. Examples are also included