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op25-legacy/python/cqpsk-demod.py

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#!/usr/bin/env python
#
# Copyright 2005,2006,2007 Free Software Foundation, Inc.
#
# cqpsk.py (C) Copyright 2009, KA1RBI
#
# This file is part of GNU Radio
#
# GNU Radio is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3, or (at your option)
# any later version.
#
# GNU Radio is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with GNU Radio; see the file COPYING. If not, write to
# the Free Software Foundation, Inc., 51 Franklin Street,
# Boston, MA 02110-1301, USA.
#
import sys
import math
from gnuradio import gr, gru, audio, eng_notation, blks2, optfir, fsk4
from gnuradio.eng_option import eng_option
from optparse import OptionParser
# accepts an input file in complex format
# applies frequency translation, resampling (interpolation/decimation)
# resampled result is CQPSK demodulated then decoded via fsk4.apco25_f()
class my_top_block(gr.top_block):
def __init__(self):
gr.top_block.__init__(self)
parser = OptionParser(option_class=eng_option)
parser.add_option("-c", "--calibration", type="int", default=0, help="freq offset")
parser.add_option("-i", "--input-file", type="string", default="in.dat", help="specify the input file")
parser.add_option("-l", "--log", action="store_true", default=False, help="dump debug .dat files")
parser.add_option("-L", "--low-pass", type="eng_float", default=15e3, help="low pass cut-off", metavar="Hz")
parser.add_option("-o", "--output-file", type="string", default="out.dat", help="specify the output file")
parser.add_option("-s", "--sample-rate", type="int", default=250000, help="input sample rate")
parser.add_option("-v", "--verbose", action="store_true", default=False, help="dump demodulation data")
(options, args) = parser.parse_args()
sample_rate = options.sample_rate
symbol_rate = 4800
sps = 10
# output rate will be 48,000
ntaps = 11 * sps
new_sample_rate = symbol_rate * sps
lcm = gru.lcm(sample_rate, new_sample_rate)
interp = lcm // sample_rate
decim = lcm // new_sample_rate
channel_taps = gr.firdes.low_pass(1.0, sample_rate, options.low_pass, options.low_pass * 0.1, gr.firdes.WIN_HANN)
FILTER = gr.freq_xlating_fir_filter_ccf(1, channel_taps, options.calibration, sample_rate)
sys.stderr.write("interp: %d decim: %d\n" %(interp, decim))
bpf_taps = gr.firdes.low_pass(1.0, sample_rate * interp, options.low_pass, options.low_pass * 0.1, gr.firdes.WIN_HANN)
INTERPOLATOR = gr.interp_fir_filter_ccf (int(interp), bpf_taps)
DECIMATOR = blks2.rational_resampler_ccf(1, int(decim))
IN = gr.file_source(gr.sizeof_gr_complex, options.input_file)
DEMOD = blks2.cqpsk_demod( samples_per_symbol = sps,
excess_bw=0.35,
costas_alpha=0.03,
gain_mu=0.05,
mu=0.05,
omega_relative_limit=0.05,
log=options.log,
verbose=options.verbose)
msgq = gr.msg_queue()
DECODER = fsk4.apco25_f(msgq,0)
self.connect(IN, FILTER, INTERPOLATOR, DECIMATOR, DEMOD, DECODER)
if __name__ == "__main__":
try:
my_top_block().run()
except KeyboardInterrupt:
tb.stop()