Patent ID: 7242710
Filing Date: 2007-07-10
Classification: H03H

Abstract:
1. A method for reduction of aliasing emerging from modifications of spectral coefficients or subband signals obtained from a digital filterbank, comprising: providing a symmetric low-pass prototype filter p building an M-channel filterbank by complex-exponential modulation of said prototype filter; where said filter has analysis and synthesis filter coefficients based on and n=0 . . . N, and k=0 . . . M−1; filtering a real-valued time domain signal through an analysis part of said filterbank; modifying complex-valued subband signals obtained from said filtering; filtering said modified complex-valued subband signals through the synthesis part of said filterbank; and taking the real part of a complex-valued time domain output signal, where said output signal is a sum of the signals obtained from said synthesis filtering; wherein said optimization of said low-pass prototype filter is accomplished by minimizing a composite objective function ε tot (α) as where α is a weighting constant, ε t is the passband error and ε a is the aliasing error; and wherein said passband error ε t is calculated as and said aliasing error ε a is calculated as where A l (e jω ), l=0 . . . M/2, are the alias gain terms evaluated on the unit circle.