Abstract-This paper develops a n improved technique for the design of analysis filters in a n M channel maximally decimated FIR perfect reconstruction QMF bank, having a lossless polyphase-component matrix E ( z ) . As in earlier work, the aim is to optimize the parameters characterizing E ( z ) until the sum of the stopband energies of the analysis filters is minimized. There a r e four new ingredients in the procedure reported here. The first is a technique for efficient initialization of one of the M analysis filters, as a spectral factor of a n Mth band filter. This factorization itself is done without root-finding techniques, in a n efficient manner using the eigenjlters approach. The second component is the initialization of the internal parameters which characterize E ( z ) , based on the above spectral factor. In earlier work, the parameters characterizing the lossless E ( z) were rotation angles, which resulted in slow convergence of the above-mentioned optimization. The third ingredient of the improved approach is a modified characterization, mostly free from rotation angles, of the lossless FIR E ( z ) . The fourth component of improvement is the incorporation of symmetry among the analysis filters, so as to minimize the number of unknown parameters being optimized. The resulting design procedure always gives better filter responses than earlier ones (for a given filter length), and converges much faster.
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