Hi, I am learning multi-channel DDC techniques using FFT. My design is referenced to http://www.pentek.com/tutorials/15_4/digdown.cfm Something in this design I do not understand. The FFT will split the input stream into N(FFT size) bins equally spaced in frequency. Totally 4 FFTs are used so that the output data rate is fs/N*4. Followed by the FFT a compensation filter is used to flatten the frequency droop at the passband edge. What I do not understand is that after FFT each bin output is a bandpass signal whose center frequency is fs/N*k (k=0:N-1). Do we need a phase shifter to translate these bandpass signals down to baseband before applying the compensation filter? I am confused on this part, I appreciate for any help.
using FFT as a channelizer
Started by ●October 20, 2009