An improved closed form design method for the cosine modulated filter banks using windowing technique

This paper presents an improved closed form method for designing cosine modulated filter banks with prescribed stopband attenuation and channel overlap. The proposed method is based on optimum passband frequency, which is calculated using empirical formulas instead of using time consuming single or multivariable optimization. Different window functions are employed to design the prototype filter with the novelty of exploiting spline functions in the transition region of the ideal filter. Several design examples are included to show the increased efficiency of the proposed method over other exiting methods in terms of computation time, amplitude distortion (eam) and aliasing distortion (ea). An application of the proposed method is considered in the area of subband coding of the ECG and speech signals.