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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, analog, blocks, digital, filter
from gnuradio.filter import firdes
from ... import manchester_sync_cc
from ...hier.rms_agc import rms_agc
from ...utils.options_block import options_block
class bpsk_demodulator(gr.hier_block2, options_block):
"""
Hierarchical block to demodulate BPSK.
The input can be either IQ or real.
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)
f_offset: Frequency offset in Hz (float)
differential: Perform non-coherent DBPSK decoding (bool)
manchester: Use Manchester coding (bool)
dump_path: Path to dump internal signals to files (str)
options: Options from argparse
"""
def __init__(self, baudrate, samp_rate, iq, f_offset=None,
differential=False, manchester=False,
dump_path=None, options=None):
gr.hier_block2.__init__(
self,
'bpsk_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)
if dump_path is not None:
dump_path = pathlib.Path(dump_path)
if manchester:
baudrate *= 2
# Prevent problems due to baudrate too high
if baudrate >= samp_rate / 4:
print(
f'Sample rate {samp_rate} sps insufficient for {baudrate} '
'baud BPSK demodulation. Demodulator will not work.',
file=sys.stderr)
baudrate = samp_rate / 4
sps = samp_rate / baudrate
max_sps = 10
if sps > max_sps:
decimation = ceil(sps / max_sps)
else:
decimation = 1
sps /= decimation
filter_cutoff = baudrate * 2.0
filter_transition = baudrate * 0.2
if f_offset is None:
f_offset = self.options.f_offset
if f_offset is None:
if iq:
f_offset = 0
elif baudrate <= 2400:
f_offset = 1500
else:
f_offset = 12000
taps = firdes.low_pass(1, samp_rate, filter_cutoff, filter_transition)
f = (filter.freq_xlating_fir_filter_ccf
if iq else filter.freq_xlating_fir_filter_fcf)
self.xlating = f(decimation, taps, f_offset, samp_rate)
agc_constant = 2e-2 / sps # This gives a time constant of 50 symbols
self.agc = rms_agc(agc_constant, 1)
if dump_path is not None:
self.agc_in = blocks.file_sink(
gr.sizeof_gr_complex, str(dump_path / 'agc_in.c64'), False)
self.agc_out = blocks.file_sink(
gr.sizeof_gr_complex, str(dump_path / 'agc_out.c64'), False)
self.connect(self.xlating, self.agc_in)
self.connect(self.agc, self.agc_out)
if not self.options.disable_fll:
fll_bw = 2*pi*decimation/samp_rate*self.options.fll_bw
self.fll = digital.fll_band_edge_cc(
sps, self.options.rrc_alpha, 100, fll_bw)
if dump_path is not None:
self.fll_freq = blocks.file_sink(
gr.sizeof_float, str(dump_path / 'fll_freq.f32'), False)
self.fll_phase = blocks.file_sink(
gr.sizeof_float, str(dump_path / 'fll_phase.f32'), False)
self.fll_error = blocks.file_sink(
gr.sizeof_float, str(dump_path / 'fll_error.f32'), False)
self.connect((self.fll, 1), self.fll_freq)
self.connect((self.fll, 2), self.fll_phase)
self.connect((self.fll, 3), self.fll_error)
nfilts = 16
rrc_taps = firdes.root_raised_cosine(
nfilts, nfilts, 1.0/float(sps), self.options.rrc_alpha,
int(ceil(11*sps*nfilts)))
# "Empiric" formula for TED gain of a PFB MF TED for complex BPSK
# 0.5 sample^{-1}
ted_gain = 0.5
damping = 1.0
self.clock_recovery = digital.symbol_sync_cc(
digital.TED_SIGNAL_TIMES_SLOPE_ML, sps, self.options.clk_bw,
damping, ted_gain, self.options.clk_limit * sps, 1,
digital.constellation_bpsk().base(), digital.IR_PFB_MF,
nfilts, rrc_taps)
if dump_path is not None:
self.clock_recovery_out = blocks.file_sink(
gr.sizeof_gr_complex,
str(dump_path / 'clock_recovery_out.c64'), 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)
self.connect(self, self.xlating, self.agc)
if self.options.disable_fll:
self.connect(self.agc, self.clock_recovery)
else:
self.connect(self.agc, self.fll, self.clock_recovery)
self.complex_to_real = blocks.complex_to_real(1)
if manchester:
self.manchester = manchester_sync_cc(
self.options.manchester_block_size)
self.connect(self.clock_recovery, self.manchester)
else:
self.manchester = self.clock_recovery
if differential:
self.delay = blocks.delay(gr.sizeof_gr_complex, 1)
self.multiply_conj = blocks.multiply_conjugate_cc(1)
sign = -1 if manchester else 1
# Take care about inverion in Manchester
self.multiply_const = blocks.multiply_const_ff(sign, 1)
self.connect(self.manchester, (self.multiply_conj, 0))
self.connect(self.manchester, self.delay, (self.multiply_conj, 1))
self.connect(self.multiply_conj, self.complex_to_real,
self.multiply_const, self)
else:
costas_bw = 2*pi/baudrate*self.options.costas_bw
self.costas = digital.costas_loop_cc(costas_bw, 2, False)
if dump_path is not None:
self.costas_out = blocks.file_sink(
gr.sizeof_gr_complex,
str(dump_path / 'costas_out.c64'), False)
self.costas_frequency = blocks.file_sink(
gr.sizeof_float,
str(dump_path / 'costas_frequency.f32'), False)
self.costas_phase = blocks.file_sink(
gr.sizeof_float,
str(dump_path / 'costas_phase.f32'), False)
self.costas_error = blocks.file_sink(
gr.sizeof_float,
str(dump_path / 'costas_error.f32'), False)
self.connect(self.costas, self.costas_out)
self.connect((self.costas, 1), self.costas_frequency)
self.connect((self.costas, 2), self.costas_phase)
self.connect((self.costas, 3), self.costas_error)
self.connect(self.manchester, self.costas,
self.complex_to_real, self)
_default_rrc_alpha = 0.35
_default_fll_bw = 25
_default_clk_rel_bw = 0.06
_default_clk_limit = 0.004
_default_costas_bw = 50
_default_manchester_block_size = 32
@classmethod
def add_options(cls, parser):
"""Adds BPSK demodulator specific options to the argparse parser"""
parser.add_argument(
'--f_offset', type=float, default=None,
help='Frequency offset (Hz) [default=1500 or 12000]')
parser.add_argument(
'--rrc_alpha', type=float, default=cls._default_rrc_alpha,
help='RRC roll-off (Hz) [default=%(default)r]')
parser.add_argument(
'--disable_fll', action='store_true', help='Disable FLL')
parser.add_argument(
'--fll_bw', type=float, default=cls._default_fll_bw,
help='FLL bandwidth (Hz) [default=%(default)r]')
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(
'--costas_bw', type=float, default=cls._default_costas_bw,
help='Costas loop bandwidth (Hz) [default=%(default)r]')
parser.add_argument(
'--manchester_block_size', type=int,
default=cls._default_manchester_block_size,
help=('Manchester recovery block size (symbols) '
'[default=%(default)r]'))
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