Alternating analysis and synthesis filters:: A new pseudo-QMF bank

The process of designing a prototype filter for a pseudo quadrature mirror filter (QMF) cosine-modulated bank can require the optimization of a highly nonlinear cost function to obtain its coefficients or the calculation of a spectral factor of a valid 2Mth band filter. This article presents a new method for designing pseudo-QMF banks in which none of the aforementioned procedures are required. To obtain the coefficients of the prototype filter we can use any technique which enables us to design linear-phase Type I or Type II FIR filters. The result is a system in which amplitude distortion is very low, there is no phase distortion at all, and aliasing is slightly higher than the stopband attenuation of the prototype filter obtained. Several examples are included. (C) 2001 Academic Press.