Apply a FIR filter and decimate the output, using an efficient polyphase structure
y = polyphase_decimation(x,h,R)
input signal (1d vector)
FIR filter coefficients (1d vector)
number of polyphase branches e.g. decimation ratio
filtered and decimated output
F.J. HARRIS, Digital Receivers and Transmitters Using Polyphase Filter Banks for Wireless Communications, 2003