Modulated M-Channel FIR Filter Banks Utilizing the Frequency Response Masking Approach

The frequency-response masking (FRM) approach was introduced as a means of generating narrow transition band linear-phase FIR filters with a low arithmetic complexity. This paper proposes an approach for synthesizing modulated maximally decimated FIR filter banks utilizing the FRM technique. For this purpose, a new class of FRM filters is introduced. Filters belonging to this class are used for synthesizing nonlinear-phase analysis and synthesis filters. Each of the analysis and synthesis filter banks is realized with the aid of two filters, a cosine modulation block, and a sine modulation block. The overall filter bank is a near perfect reconstruction (NPR) filter bank. The distortion function has a linear phase response but a small magnitude distortion. Further, the filter bank has small aliasing errors. The magnitude distortion and aliasing errors can be made arbitrarily small by properly designing a prototype filter. Compared with conventional cosine modulated filter banks, the proposed ones lower significantly the overall arithmetic complexity at the expense of a slightly increased overall filter bank delay in applications requiring narrow transition bands. Examples are included illustrating the benefits provided by the proposed filter banks.