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#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# Copyright 2019 Daniel Estevez <daniel@destevez.net>
#
# This file is part of gr-satellites
#
# SPDX-License-Identifier: GPL-3.0-or-later
#
from math import ceil, pi
import pathlib
import sys
from gnuradio import gr, blocks, analog, digital, filter
from gnuradio.filter import firdes
import numpy as np
from ...hier.rms_agc_f import rms_agc_f
from ...utils.options_block import options_block
class fsk_demodulator(gr.hier_block2, options_block):
"""
Hierarchical block to demodulate FSK.
The input can be either IQ or real. For IQ input, it is assumed
that the data is FM modulated, so FM demodulation is performed.
For real input, it is assumed that the data is already FM
demodulated.
Args:
baudrate: Baudrate in symbols per second (float)
sample_rate: Sample rate in samples per second (float)
iq: Whether the input is IQ or real (bool)
deviation: Deviation in Hz, negative inverts sidebands (float)
subaudio: Use subaudio demodulation (bool)
dc_block: Use DC-block (bool)
dump_path: Path to dump internal signals to files (str)
options: Options from argparse
"""
def __init__(self, baudrate, samp_rate, iq, deviation=None,
subaudio=False, dc_block=True, dump_path=None,
options=None):
gr.hier_block2.__init__(
self,
'fsk_demodulator',
gr.io_signature(1, 1,
gr.sizeof_gr_complex if iq else gr.sizeof_float),
gr.io_signature(1, 1, gr.sizeof_float))
options_block.__init__(self, options)
use_agc = self.options.use_agc or not iq
if self.options.disable_dc_block:
dc_block = False
if dump_path is not None:
dump_path = pathlib.Path(dump_path)
if deviation is not None:
_deviation = deviation
else:
_deviation = self.options.deviation
# Prevent problems due to baudrate too high
if baudrate >= samp_rate:
print(f'Sample rate {samp_rate} sps insufficient for {baudrate} '
'baud FSK demodulation. Demodulator will not work.',
file=sys.stderr)
baudrate = samp_rate / 2
if iq:
# Cut to Carson's bandwidth rule before quadrature demod.
# Note that _deviation can be negative to encode that the
# low tone corresponds to the symbol 1 and the high tone
# corresponds to the symbol 0.
carson_cutoff = abs(_deviation) + baudrate / 2
self.demod = analog.quadrature_demod_cf(
samp_rate/(2*pi*_deviation))
if carson_cutoff >= samp_rate / 2:
# Sample rate is already narrower than Carson's
# bandwidth. Do not filter
self.connect(self, self.demod)
else:
# Sample rate is wider than Carson's bandwidth.
# Lowpass filter before demod.
fir_taps = firdes.low_pass(
1, samp_rate, carson_cutoff, 0.1 * carson_cutoff)
self.demod_filter = filter.fir_filter_ccf(1, fir_taps)
self.connect(self, self.demod_filter, self.demod)
else:
self.demod = self
sps = samp_rate / baudrate
max_sps = 10
if sps > max_sps:
decimation = ceil(sps / max_sps)
else:
decimation = 1
sps /= decimation
if subaudio:
# some not-so-bad filter parameters for subaudio processing
subaudio_cutoff = 2.0/3.0 * baudrate
subaudio_transition = subaudio_cutoff / 4.0
subaudio_taps = firdes.low_pass(
1, samp_rate, subaudio_cutoff, subaudio_transition)
self.subaudio_lowpass = filter.fir_filter_fff(1, subaudio_taps)
# square pulse filter
sqfilter_len = int(samp_rate / baudrate)
taps = np.ones(sqfilter_len)/sqfilter_len
self.lowpass = filter.fir_filter_fff(decimation, taps)
if dc_block:
self.dcblock = filter.dc_blocker_ff(ceil(sps * 32), True)
else:
self.dcblock = self.lowpass # to simplify connections below
if use_agc:
# This gives a time constant of 50 symbols
agc_constant = 2e-2 / sps
self.agc = rms_agc_f(agc_constant, 1)
if dump_path is not None:
self.waveform = blocks.file_sink(
gr.sizeof_float, str(dump_path / 'waveform.f32'))
# "Eempiric" formula for TED gain of Gardner detector
# 1.47 symbol^{-1}
ted_gain = 1.47
damping = 1.0
self.clock_recovery = digital.symbol_sync_ff(
digital.TED_GARDNER, sps, self.options.clk_bw, damping, ted_gain,
self.options.clk_limit * sps, 1,
digital.constellation_bpsk().base(), digital.IR_PFB_NO_MF)
if dump_path is not None:
self.clock_recovery_out = blocks.file_sink(
gr.sizeof_float,
str(dump_path / 'clock_recovery_out.f32'), False)
self.clock_recovery_err = blocks.file_sink(
gr.sizeof_float,
str(dump_path / 'clock_recovery_err.f32'), False)
self.clock_recovery_T_inst = blocks.file_sink(
gr.sizeof_float,
str(dump_path / 'clock_recovery_T_inst.f32'), False)
self.clock_recovery_T_avg = blocks.file_sink(
gr.sizeof_float,
str(dump_path / 'clock_recovery_T_avg.f32'), False)
self.connect(self.clock_recovery, self.clock_recovery_out)
self.connect((self.clock_recovery, 1), self.clock_recovery_err)
self.connect((self.clock_recovery, 2), self.clock_recovery_T_inst)
self.connect((self.clock_recovery, 3), self.clock_recovery_T_avg)
conns = [self.demod]
if subaudio:
conns.append(self.subaudio_lowpass)
conns.append(self.lowpass)
if dc_block:
conns.append(self.dcblock)
self.connect(*conns)
if use_agc:
self.connect(self.dcblock, self.agc, self.clock_recovery)
if dump_path is not None:
self.connect(self.agc, self.waveform)
else:
self.connect(self.dcblock, self.clock_recovery)
if dump_path is not None:
self.connect(self.dcblock, self.waveform)
if not iq and _deviation < 0:
# when working with FM-demodulated input, if the deviation is
# negative, the polarity of the signal needs to be inverted.
self.invert_polarity = blocks.multiply_const_ff(-1, 1)
self.connect(self.clock_recovery, self.invert_polarity, self)
else:
self.connect(self.clock_recovery, self)
_default_clk_rel_bw = 0.06
_default_clk_limit = 0.004
_default_deviation_hz = 5000
@classmethod
def add_options(cls, parser):
"""
Adds FSK demodulator specific options to the argparse parser
"""
parser.add_argument(
'--clk_bw', type=float, default=cls._default_clk_rel_bw,
help=('Clock recovery bandwidth (relative to baudrate) '
'[default=%(default)r]'))
parser.add_argument(
'--clk_limit', type=float, default=cls._default_clk_limit,
help=('Clock recovery limit (relative to baudrate) '
'[default=%(default)r]'))
parser.add_argument(
'--deviation', type=float, default=cls._default_deviation_hz,
help='Deviation (Hz) [default=%(default)r]')
parser.add_argument(
'--use_agc', action='store_true',
help='Use AGC (for IQ input. AGC always on for real input)')
parser.add_argument(
'--disable_dc_block', action='store_true',
help='Disable DC block')
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