General design of nearly perfect polyphase filter banks

In a polyphase approach of filter banks with critical sampling, it is proposed to design and implement the elements of the synthesis section as approximations of the inverses of the elements in the analysis section. The conditions for such approximations to be valid are stated and a design procedure is described, along with the corresponding structure. The approach generalises theqmf method by adding more flexibility, since it relaxes the constraints on the analysis prototype filter specification and allows different complexities in both sections. The general approach can yield de-signs able to compete favourably withqmf and pseudo-QMF in many aspects.