Closed form design of prototype filters for linear phase DFT polyphase filter banks

A complex modulated subband coding filter bank with almost perfect reconstruction is discussed. It is realized by means of discrete Fourier transform (DFT) polyphase filter banks with high computational efficiency. In the analysis and the synthesis part of the filter bank, the same linear phase prototype filters are used. A closed-form design of the prototype filter is presented in the form of a square root raised-cosine function weighted by a Hamming window. This design method provides small amplitude and aliasing distortion with few filter coefficients, and enables a trade-off between the two different kinds of distortion.<>