Lowpass filter in receive_path.py



In receive_path.py, there is this code:

Design filter to get actual channel we want

sw_decim = 1
chan_coeffs = gr.firdes.low_pass (1.0, # gain
sw_decim * self._samples_per_symbol,
# sampling rate
1.0, # midpoint of trans. band
0.1, # width of trans. band
gr.firdes.WIN_HANN) # filter type

So, the approximate pass-band of this filter is from 0 Hz to 1 Hz. Isn’t
this a little small? (Input signal must have extremely small bandwidth
pass through.)

In am_rcv.py, and other codes the pass-band is more understandable, like
9e3 Hz = midpoint of transition band.

Jonathan Shan


no I don’t understand this either.