Design of Multiplierless Lattice QMF: Structure and Algorithm Development

In this brief, efficient multiplierless design of lattice quadrature mirror filter bank is presented. Previous work by the authors has shown that splitting each lattice stage into cascade of subrotations results in larger stopband attenuation of filter than the conventional direct quantization. This brief extends the work further by exploiting the subrotations which yield more flexible sum of signed powers-of-two quantization. This enables us to find more possible discrete representations, and hence to reduce the quantization error. Also, an algorithm for the efficient gathering of candidate discrete coefficients is developed, based on the trellis-based searching approach. It substantially alleviates the overheads of optimization program, especially when the wordlengths and the number of nonzero digits are large. Several design examples are provided to show that the proposed structure with the candidate gathering algorithm provides improved frequency response.