This paper describes a technique for designing uniform and non-uniform filterbanks based on the Running Fourier Transform (RFT). The RFT is implemented by convolving the input signal with one of a family of windows, h(nT) = (nT)ke-anT, where k and a may be chosen to specify the order and bandwidth, respectively, of each analysing filter. An expression for the equivalent composite impulse response has been derived which can be used to optimise its composite amplitude and phase responses. Non-uniform filterbanks can be designed by splitting the frequency band of interest into a number of uniform sections and then optimising the equivalent composite impulse response of each section. Finally, a modified cepstral smoothing technique for non-uniform spectra is presented and shown to be superior to conventional bi-pass filtering.
Bibliographic reference. Owens, F. J. / Murphy, M. S. (1989): "Non-uniform RFT filterbank design for speech processing", In EUROSPEECH-1989, 1605-1608.