p25 demodulator hier py block
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#
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# Copyright 2005,2006,2007 Free Software Foundation, Inc.
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#
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# OP25 Demodulator Block
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# Copyright 2009, 2010, 2011, 2012, 2013, 2014 Max H. Parke KA1RBI
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#
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# This file is part of GNU Radio and part of OP25
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#
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# This is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 3, or (at your option)
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# any later version.
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#
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# It is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this; see the file COPYING. If not, write to
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# the Free Software Foundation, Inc., 51 Franklin Street,
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# Boston, MA 02110-1301, USA.
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#
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"""
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P25 C4FM/CQPSK demodulation block.
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"""
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from gnuradio import gr, gru, eng_notation
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from gnuradio import filter, analog, digital, blocks
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from gnuradio.eng_option import eng_option
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import op25
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import op25_repeater
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from math import pi
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# default values (used in __init__ and add_options)
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_def_output_sample_rate = 48000
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_def_excess_bw = 0.1
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_def_if_rate = 24000
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_def_gain_mu = 0.025
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_def_costas_alpha = 0.04
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_def_symbol_rate = 4800
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_def_symbol_deviation = 600.0
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# /////////////////////////////////////////////////////////////////////////////
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# demodulator
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# /////////////////////////////////////////////////////////////////////////////
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class p25_demod_cb(gr.hier_block2):
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def __init__(self,
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input_rate = None,
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demod_type = 'cqpsk',
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relative_freq = 0,
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offset = 0,
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if_rate = _def_if_rate,
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gain_mu = _def_gain_mu,
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costas_alpha = _def_costas_alpha,
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symbol_rate = _def_symbol_rate):
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"""
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Hierarchical block for P25 demodulation.
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The complex input is tuned, decimated and demodulated
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@param input_rate: sample rate of complex input channel
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@type input_rate: int
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"""
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gr.hier_block2.__init__(self, "p25_demod_c",
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gr.io_signature(1, 1, gr.sizeof_gr_complex), # Input signature
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gr.io_signature(1, 1, gr.sizeof_char)) # Output signature
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# gr.io_signature(0, 0, 0)) # Output signature
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self.input_rate = input_rate
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self.if_rate = if_rate
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self.symbol_rate = symbol_rate
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self.connect_state = None
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self.offset = 0
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self.sps = 0.0
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self.lo_freq = 0
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# local osc
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self.lo = analog.sig_source_c (input_rate, analog.GR_SIN_WAVE, 0, 1.0, 0)
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self.mixer = blocks.multiply_cc()
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lpf_coeffs = filter.firdes.low_pass(1.0, input_rate, 15000, 1500, filter.firdes.WIN_HANN)
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decimation = int(input_rate / if_rate)
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self.lpf = filter.fir_filter_ccf(decimation, lpf_coeffs)
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resampled_rate = float(input_rate) / float(decimation) # rate at output of self.lpf
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self.arb_resampler = filter.pfb.arb_resampler_ccf(
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float(self.if_rate) / resampled_rate)
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self.connect(self, (self.mixer, 0))
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self.connect(self.lo, (self.mixer, 1))
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self.connect(self.mixer, self.lpf, self.arb_resampler)
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levels = [ -2.0, 0.0, 2.0, 4.0 ]
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self.slicer = op25_repeater.fsk4_slicer_fb(levels)
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fm_demod_gain = self.if_rate / (2.0 * pi * _def_symbol_deviation)
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self.fm_demod = analog.quadrature_demod_cf(fm_demod_gain)
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sps = int(self.if_rate // self.symbol_rate)
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symbol_decim = 1
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ntaps = 11 * sps
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rrc_coeffs = (1.0/sps,)*sps
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self.symbol_filter = filter.fir_filter_fff(symbol_decim, rrc_coeffs)
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autotuneq = gr.msg_queue(2)
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self.fsk4_demod = op25.fsk4_demod_ff(autotuneq, self.if_rate, self.symbol_rate)
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omega = float(self.if_rate) / float(self.symbol_rate)
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gain_omega = 0.1 * gain_mu * gain_mu
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alpha = costas_alpha
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beta = 0.125 * alpha * alpha
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fmax = 2400 # Hz
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fmax = 2*pi * fmax / float(self.if_rate)
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self.clock = op25_repeater.gardner_costas_cc(omega, gain_mu, gain_omega, alpha, beta, fmax, -fmax)
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self.agc = analog.feedforward_agc_cc(16, 1.0)
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# Perform Differential decoding on the constellation
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self.diffdec = digital.diff_phasor_cc()
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# take angle of the difference (in radians)
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self.to_float = blocks.complex_to_arg()
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# convert from radians such that signal is in -3/-1/+1/+3
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self.rescale = blocks.multiply_const_ff( (1 / (pi / 4)) )
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self.connect_chain(demod_type)
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self.connect(self.slicer, self)
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self.set_relative_frequency(relative_freq)
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def set_omega(self, omega):
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sps = self.if_rate / float(omega)
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if sps == self.sps:
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return
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self.sps = sps
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print 'set_omega %d %f' % (omega, sps)
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self.clock.set_omega(self.sps)
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def set_relative_frequency(self, freq):
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if abs(freq) > self.input_rate/2:
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#print 'set_relative_frequency: error, relative frequency %d exceeds limit %d' % (freq, self.input_rate/2)
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return False
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if freq == self.lo_freq:
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return True
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#print 'set_relative_frequency', freq
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self.lo_freq = freq
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self.lo.set_frequency(self.lo_freq)
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return True
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def set_output(self, slot, filename):
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print 'set_output', slot, filename
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def release(self):
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print 'release'
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# assumes lock held or init
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def disconnect_chain(self):
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if self.connect_state == 'cqpsk':
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self.disconnect(self.arb_resampler, self.agc, self.clock, self.diffdec, self.to_float, self.rescale, self.slicer)
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elif self.connect_state == 'fsk4':
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self.disconnect(self.arb_resampler, self.fm_demod, self.symbol_filter, self.fsk4_demod, self.slicer)
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self.connect_state = None
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# assumes lock held or init
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def connect_chain(self, demod_type):
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if self.connect_state == demod_type:
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return # already in desired state
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self.disconnect_chain()
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self.connect_state = demod_type
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if demod_type == 'fsk4':
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self.connect(self.arb_resampler, self.fm_demod, self.symbol_filter, self.fsk4_demod, self.slicer)
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elif demod_type == 'cqpsk':
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self.connect(self.arb_resampler, self.agc, self.clock, self.diffdec, self.to_float, self.rescale, self.slicer)
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else:
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print 'connect_chain failed, type: %s' % demod_type
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