Highly adjustable multirate digital filters based on fast convolution

Abstract

FFT-IFFT configuration, or more generally a forward-inverse orthogonal transform pair, offers a way to implement a digital filter whose frequency-domain characteristics can be straightforwardly tuned by adjusting the complex gains of the frequency bins. Using filter banks (FBs) for the transform pair, sharp transition bands can be obtained for low-pass/bandpass/highpass type filter designs. However, FBs suffer from relatively high implementation complexity. Fast convolution based multirate FBs constitute and alternative approach which is able to reach high spectral containment together with high flexibility and conceptual simplicity. In this paper we consider a fast convolution based highly tunable analysis FB configuration and show that nearly perfect-reconstruction FB systems can be implemented using this approach. Further, the channel filters of the analysis FB are easily configurable for different bandwidths, center frequencies and output sampling rates.