Application of DFT filter banks and cosine modulated filter banks in filtering

Abstract

In this paper, we introduce a new under-decimated system. A filter bank is said to be under-decimated if the number of channels is more than the decimation ratio in the subbands. Two types of low-complexity filter banks can be used for the new system, the DFT filter bank and cosine modulated filter bank. The setup of the under-decimated system has 2M channels but is decimated only by M. In both the DFT filter bank case and cosine modulated filter bank case, the system is approximately alias free and the overall response is equivalent to a tunable multilevel filter. The properties of DFT filter banks and cosine modulated filter banks can be exploited to simultaneously achieve parallelism, computational saving and lower working rate. Furthermore, in both filter banks the implementation cost of the analysis bank is comparable to that of one prototype filter plus some low complexity matrices. The individual analysis and synthesis filters have complex coefficients in the DFT filter bank but have real coefficients in the cosine modulated filter bank.