Appendix G: Polyphase filter design
Alois M. Bock · Institution of Engineering and Technology eBooks · 2009
Design an FIR low-pass filter with a bandwidth of fsi/2N, where fsi is the input sampling frequency. The filter can be designed by inverse Fourier transforming the theoretical frequency response of the low-pass filter. Since the theoretical frequency response is a square wave, the inverse Fourier transform generates a sin(x)/x waveform of infinite length. After transformation into the spatial domain, a window function has to be applied to limit the number of filter coefficients.