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use the new cutoff parameter to compensate the fractional decimator

This commit is contained in:
Jakob Ketterl 2021-07-25 23:38:24 +02:00
parent 75aac5969a
commit 11a3606070
1 changed files with 4 additions and 1 deletions
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5
csdr/chain/demodulator.py
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@ -10,7 +10,10 @@ class DemodulatorChain(Chain):
decimation, fraction = self._getDecimation(samp_rate, audioRate)
if_samp_rate = samp_rate / decimation
transition = 0.15 * (if_samp_rate / float(samp_rate))
self.decimation = FirDecimate(decimation, transition)
# set the cutoff on the fist decimation stage lower so that the resulting output
# is already prepared for the second (fractional) decimation stage.
# this spares us a second filter.
self.decimation = FirDecimate(decimation, transition, 0.5 * decimation / (samp_rate / audioRate))
bp_transition = 320.0 / audioRate
self.bandpass = Bandpass(transition=bp_transition, use_fft=True)