On implementation and design of filter banks for subband adaptive systems

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/spl les/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 underpinned by simulation results.