A low-order IIR QMF banks design with a delay selection procedure

An effective and efficient method for designing near perfect reconstruction low-order IIR QMF banks is presented in this paper. The QMF bank design problem is first converted to an equalizer design optimization problem and described in the polyphase representation, so the optimization variables are reduced by half, and significant reduction of computation load is achieved for high-order system. The QMF bank delay in the optimization problem is selected based on the result of a least square estimation problem. High-order optimal FIR solutions are then obtained by formulating the H₂/H_∞/mixed-norm minimization problems in the linear matrix inequality framework. Finally, approximate low-order IIR solutions are obtained by applying balanced realization and model order reduction techniques.