A modified design to eliminate passband anomaly in weighted minimax quadrature mirror filters

It is known that quadrature mirror filters (QMFs) designed using the algorithm in Lim and Yang (1993) suffer from passband anomaly under certain conditions. A modification to this algorithm was proposed in Goh et al. (1996) to overcome this anomaly. However, this design is not a general solution for different stopband edge frequencies. In this paper, we propose a more robust technique to design QMFs, by modifying the frequency domain approach proposed in Lim and Yang with a better initial guess filter obtained by frequency sampling design. The QMF designed employing the proposed technique overcomes the passband anomaly and has excellent frequency response characteristics that are considerably better than those obtained using earlier methods.