Analysis of a delayless subband adaptive filter

Abstract

An analysis of a delayless subband adaptive digital filter (ADF) structure is presented. In this structure adaptive weights in each subband are computed by the LMS algorithm and then transformed into those in fullband by the Hadamard transform. The conventional subband ADF has transmission delay and aliasing effects associated with the filter bank. However in this manner such defects are avoided while retaining the computational and convergence speed advantages of subband decomposition. In addition the overall transfer function of the novel type of subband ADF is strictly equivalent to that of the Wiener filter for the fullband ADF. Also, a characteristic equation is derived to discuss the stability of the adaptation algorithm. Some numerical results show the good performance of this scheme.