An improved structure and design procedure for signed power-of-two lattice QMF bank

In this paper, an improved structure and design procedure for signed power-of-two (SPT) lattice quadrature mirror filter (QMF) bank is presented. Previous work by the authors has shown that the angle quantization method of lattice coefficient results in a lower approximation error than the direct quantization. This paper extends the work by exploiting the rotations which yield more possible sum of SPT representations. This enable us to reduce the approximation error further. Also, an algorithm for the efficient gathering of candidate discrete coefficients based on the trellis based searching (TBS) approach is developed in order to alleviate the overheads of optimization program. Design examples are given to show that the proposed structure and algorithm provide larger stopband attenuation of filter than the existing methods.