A generalized design of quadrature mirror filters

It was reported previously that the quadrature mirror filters (QMF) designed using the weighted least squares (WLS) algorithm presented by Lim and Yang (1993) suffers from pass-band anomaly, under certain conditions. A modification of this algorithm, incorporating an additional term to the objective function of the WLS optimization technique, to overcome this anomaly was proposed by Goh, Lim and Ng (1996). However, the solution obtained by this method for specific stop-band edge frequency fails for another filter with different stop-band edge frequency and hence lacks the design generality. In this paper, we propose a generalized technique, modifying the frequency domain approach of Chen and Lee (1992), with a better initial guess filter obtained by the frequency sampling design. The resulting QMF overcome the pass-band anomaly reported by Lim et al. and have excellent frequency response characteristics that is considerably better than that of the filters obtained in all the above methods.