57 lines
1.8 KiB
Python
57 lines
1.8 KiB
Python
from csdr.chain import Chain
|
|
from pycsdr.modules import Shift, FirDecimate, Bandpass, Squelch, FractionalDecimator
|
|
from abc import ABCMeta, abstractmethod
|
|
|
|
|
|
class Demodulator(Chain, metaclass=ABCMeta):
|
|
@abstractmethod
|
|
def setLastDecimation(self, decimation: Chain):
|
|
pass
|
|
|
|
|
|
class DemodulatorChain(Chain):
|
|
def __init__(self, samp_rate: int, audioRate: int, shiftRate: float, demodulator: Demodulator):
|
|
self.shift = Shift(shiftRate)
|
|
|
|
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)
|
|
|
|
bp_transition = 320.0 / if_samp_rate
|
|
self.bandpass = Bandpass(bp_transition, use_fft=True)
|
|
|
|
self.squelch = Squelch(5)
|
|
|
|
if fraction != 1.0:
|
|
demodulator.setLastDecimation(Chain(FractionalDecimator(fraction)))
|
|
|
|
workers = [
|
|
self.shift,
|
|
self.decimation,
|
|
self.bandpass,
|
|
self.squelch,
|
|
demodulator
|
|
]
|
|
|
|
super().__init__(*workers)
|
|
|
|
def setShiftRate(self, rate: float):
|
|
self.shift.setRate(rate)
|
|
|
|
def setSquelchLevel(self, level: float):
|
|
self.squelch.setSquelchLevel(level)
|
|
|
|
def setBandpass(self, low_cut: float, high_cut: float):
|
|
self.bandpass.setBandpass(low_cut, high_cut)
|
|
|
|
def _getDecimation(self, input_rate, output_rate):
|
|
if output_rate <= 0:
|
|
raise ValueError("invalid output rate: {rate}".format(rate=output_rate))
|
|
decimation = 1
|
|
target_rate = output_rate
|
|
while input_rate / (decimation + 1) >= target_rate:
|
|
decimation += 1
|
|
fraction = float(input_rate / decimation) / output_rate
|
|
return decimation, fraction
|