Recursive digital filters and two-channel filter banks: Frequency-response masking approach

摘要

In this paper, we present the application of frequency-response masking (FRM) technique in constructing digital filters and two-channel filter banks. With the FRM approach, digital filters with sharp transition bands and two-channel filter banks with narrow transition bands between the channels can be achieved. The FRM structure considered in this paper is composed of IIR model filters and linear-phase FIR masking filters. The efficient structures for analysis and synthesis banks consisting of all-pass sub-filters and polyphase components of masking filters are obtained. We particularly consider the frequency responses of filters and filter banks when the IIR model filters are of approximately linear phase. It is shown that by using an FRM-based two-channel filter bank and an additional set of masking filters, the two-stage very selective filters and two-channel filter banks can be developed. It is shown by means of examples that the usage of IIR model filters reduces the computational complexity and decreases the overall group delay as compared with an equivalent FRM structure based on FIR filters only.