Creation of a polyphase decimation filter structure
H = polyphase_filter(h,m)
FIR filter coefficients (1d vector)
number of polyphase branches e.g. decimation ratio
resulting polyphase matrix form
Creation of the polyphase matrix. The filter is decomposed into m phases sub-filters (m rows of the H matrix). Each sub-filter can process a decimated version of the input signal, with a different phase.