In this paper we propose a new strategy for the design of real-valued lterbanks which avoids aliasing in the subbands (\inband aliasing") such that applications where two subband signals have to be compared become possible. One example for such an application is subband adaptive ltering, where, with the proposed lterbank structure, the traditionally required crossterm adaptive lters between adjacent subbands can be omitted. The proposed lterbank consists of at least three channels which are subsampled by di erent subsampling ratios.
-In this paper, we introduce a polyphase implementation and design of an oversampled K-channel generalized DFT (GDFT) filter bank, which can be employed for subband adaptive filtering, and therefore is required to have a low aliasing level in the subband signals. A polyphase structure is derived which can be factorized into a real valued polyphase network and a GDFT modulation. For the latter, an FFT realization may be used, yielding a very inexpensive polyphase implementation for arbitrary integer decimation ratios N 5 K. We also present an analysis underlining the efficiency of complex valued subband processing. The design of the filter bank is completely based on the prototype filter and solved using a fast converging iterative least squares method, for which we give examples. The design specifications closely correspond with performance limits of subband adaptive filtering, which are under-pinned by simulation results.
Recently a new real-valued oversampled filter bank has been proposed which reduces the "inband" alias. The filter bank consists of at least three channels which are subsampled by different subsampling ratios. In this paper we investigate into the applicability of this filter bank for adaptive subband filtering and compare the setup with existing subband and fullband techniques.
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