Parametric phase equalizers for warped filter-banks

In this paper, phase equalizers are investigated which aim to compensate the non-linear phase response of a frequency warped filter-bank and a new design is proposed. The frequency resolution of a warped filter-bank based on an allpass transformation can be adjusted by a single allpass coefficient. Thus, parametric phase equalizers are of special interest as their coefficients are given by a closed-form expression in dependence on this allpass coefficient. The approximation error for parametric FIR phase equalizers is analyzed. They can achieve a low phase error but introduce magnitude distortions. These distortions can be avoided by using allpass phase equalizers. A new parametric allpass phase equalizer is proposed. It has a lower complexity than a general allpass phase equalizer and leads to an equiripple approximation error for the desired phase response and group-delay.