Simple design of oversampled uniform DFT filter banks with applications to subband acoustic echo cancellation

Abstract

Subband adaptive filtering, which is the basis of modern acoustic echo cancellation (AEC) systems, is an important application of filter banks in which critical sampling cannot be used in general because of decimation aliasing effects. This leads to the use of oversampling schemes in the filter bank design wherein the perfect-reconstruction (PR) or near PR property is still required. In this work, a simple design technique for uniform DFT filter bank with near PR property is presented for the purpose of subband adaptive filtering. The prototype filter in the proposed filter banks is derived simply by performing an interpolation of a two-channel QMF filter, which can be obtained easily by computation or table look-up. An efficient implementation of the filter banks based on a weighted-overlap-add structure is described that allows flexibility in oversampling. The filter bank design technique presented in this paper is of particular interest in engineering applications, as demonstrated by design examples and experimental results in a real-time subband AEC application.