Design of oversampled DFT filter banks with minimum delay

When a filter bank satisfies the conditions for perfect reconstruction, the whole transfer function has the property of a single delay, In the application to subband adaptive filters and other problems, this delay is directly reflected, for example, in the transfer delay of the speech signal. This paper considers an oversampled DFT filter bank, where the number of channels is an integer multiple of the decimation ratio. The delay is investigated, and a design method is presented for a filter bank with minimum delay. As the first step, the minimum delay of the filter bank satisfying the conditions of perfect reconstruction and causality is given by the number of channels minus 1, regardless of the decimation ratio or the number of filter taps. The design method for the filter bank with this minimum delay is formulated. Lastly, a detailed design example is presented and the effectiveness of the proposed method is verified. (C) 1998 Scripta Technica.