EQUIRIPPLE DESIGN OF QMF BANKS USING DIGITAL ALLPASS NETWORKS

In this paper, we discuss design of quadrature mirror filter (QMF) ban ks using digital allpass networks in the frequency domain. In the QMF banks composed of a parallel connection of two allpass networks, both aliasing error and amplitude distortion are always completely canceled . Therefore, we only need to design the analysis filters and eliminate phase distortion of the overall transfer function. We consider design of the QMF banks in two cases where phase responses of the filters ar e required or not required. In the case where the phase responses are not required, the design problem can be reduced to design of phase dif ference of two allpass networks. In the case where the phase responses are required, we present a procedure for designing the QMF banks with both equiripple magnitude and phase responses.