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

A filter bank is said to be under-decimated if the number of channels is more than the decimation ratio in the subbands. This paper introduces a new under-decimated system where two types of low-complexity filter banks can be used, the DFT filter bank and cosine modulated filter bank. In both cases, the system is approximately alias-free and overall response is equivalent to a tunable multilevel filter. Properties of the DFT filter banks and the 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.