A Class of Cosine-Modulated Filter Banks with Multiple Prototype Filters

In this paper, several new cosine-modulated filter banks (CMFBs) are developed by using multiple prototype filters in conjunction with a proper modulation scheme. First, the conventional CMFB is formulated as a cascade of a modulation matrix and a polyphase matrix with a bidiagonal structure. Under this framework, it is then revealed that the proposed new CMFBs are a special class of paraunitary filter banks (PUFBs), whose polyphase matrices are of different sparse patterns. It is shown that when M prototype filters are used, a full polyphase matrix representing a general PUFB can be obtained, thus providing a bridge connecting CMFBs and PUFBs. It is also shown that with more free parameters involved in the CMFBs, one can achieve a tradeoff between the performance of the filter bank and its design/implementation complexity