A new delayless subband adaptive filter structure

Adaptive subband techniques have been developed to reduce complexity and sl ow convergence problems of the traditional fullband high-order adaptive fil ters, Some of the disadvantages often encountered in most of the proposed a rchitectures are the effect of aliasing associated with the multirate struc ture, which is a source of error in the modeling of the unknown system, and the delay introduced in the signal path. In this paper, we present a new d elayless maximally decimated structure where the optimal subband filters ar e related to the wideband system in a closed form. They make use of a speci al DFT analysis filterbank where the polyphase components of the prototype filter represent fractional delays so that there is no need for adaptive cr oss-filters, and the unknown system can modeled perfectly in a closed-loop scheme. We interpret the proposed structure as a special case of a block ad aptive filter with low er computational complexity than the conventional fu llband LMS algorithm. Some computer simulations are presented in order to v erify the good features of the proposed structure.