--- /dev/null
+#
+# GMSK modulation and demodulation.
+#
+#
+# Copyright 2005,2006,2007 Free Software Foundation, Inc.
+#
+# 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.
+#
+
+# See gnuradio-examples/python/digital for examples
+
+from gnuradio import gr
+from gnuradio import modulation_utils
+from math import pi
+import numpy
+from pprint import pprint
+import inspect
+
+# default values (used in __init__ and add_options)
+_def_samples_per_symbol = 2
+_def_bt = 0.35
+_def_verbose = False
+_def_log = False
+
+_def_gain_mu = None
+_def_mu = 0.5
+_def_freq_error = 0.0
+_def_omega_relative_limit = 0.005
+
+
+# /////////////////////////////////////////////////////////////////////////////
+# GMSK modulator
+# /////////////////////////////////////////////////////////////////////////////
+
+class gmsk_mod(gr.hier_block2):
+
+ def __init__(self,
+ samples_per_symbol=_def_samples_per_symbol,
+ bt=_def_bt,
+ verbose=_def_verbose,
+ log=_def_log):
+ """
+ Hierarchical block for Gaussian Minimum Shift Key (GMSK)
+ modulation.
+
+ The input is a byte stream (unsigned char) and the
+ output is the complex modulated signal at baseband.
+
+ @param samples_per_symbol: samples per baud >= 2
+ @type samples_per_symbol: integer
+ @param bt: Gaussian filter bandwidth * symbol time
+ @type bt: float
+ @param verbose: Print information about modulator?
+ @type verbose: bool
+ @param debug: Print modualtion data to files?
+ @type debug: bool
+ """
+
+ gr.hier_block2.__init__(self, "gmsk_mod",
+ gr.io_signature(1, 1, gr.sizeof_char), # Input signature
+ gr.io_signature(1, 1, gr.sizeof_gr_complex)) # Output signature
+
+ self._samples_per_symbol = samples_per_symbol
+ self._bt = bt
+
+ if not isinstance(samples_per_symbol, int) or samples_per_symbol < 2:
+ raise TypeError, ("samples_per_symbol must be an integer >= 2, is %r" % (samples_per_symbol,))
+
+ ntaps = 4 * samples_per_symbol # up to 3 bits in filter at once
+ sensitivity = (pi / 2) / samples_per_symbol # phase change per bit = pi / 2
+
+ # Turn it into NRZ data.
+ self.nrz = gr.bytes_to_syms()
+
+ # Form Gaussian filter
+ # Generate Gaussian response (Needs to be convolved with window below).
+ self.gaussian_taps = gr.firdes.gaussian(
+ 1, # gain
+ samples_per_symbol, # symbol_rate
+ bt, # bandwidth * symbol time
+ ntaps # number of taps
+ )
+
+ self.sqwave = (1,) * samples_per_symbol # rectangular window
+ self.taps = numpy.convolve(numpy.array(self.gaussian_taps),numpy.array(self.sqwave))
+ self.gaussian_filter = gr.interp_fir_filter_fff(samples_per_symbol, self.taps)
+
+ # FM modulation
+ self.fmmod = gr.frequency_modulator_fc(sensitivity)
+
+ if verbose:
+ self._print_verbage()
+
+ if log:
+ self._setup_logging()
+
+ # Connect & Initialize base class
+ self.connect(self, self.nrz, self.gaussian_filter, self.fmmod, self)
+
+ def samples_per_symbol(self):
+ return self._samples_per_symbol
+
+ def bits_per_symbol(self=None): # staticmethod that's also callable on an instance
+ return 1
+ bits_per_symbol = staticmethod(bits_per_symbol) # make it a static method.
+
+
+ def _print_verbage(self):
+ print "bits per symbol = %d" % self.bits_per_symbol()
+ print "Gaussian filter bt = %.2f" % self._bt
+
+
+ def _setup_logging(self):
+ print "Modulation logging turned on."
+ self.connect(self.nrz,
+ gr.file_sink(gr.sizeof_float, "nrz.dat"))
+ self.connect(self.gaussian_filter,
+ gr.file_sink(gr.sizeof_float, "gaussian_filter.dat"))
+ self.connect(self.fmmod,
+ gr.file_sink(gr.sizeof_gr_complex, "fmmod.dat"))
+
+
+ def add_options(parser):
+ """
+ Adds GMSK modulation-specific options to the standard parser
+ """
+ parser.add_option("", "--bt", type="float", default=_def_bt,
+ help="set bandwidth-time product [default=%default] (GMSK)")
+ add_options=staticmethod(add_options)
+
+
+ def extract_kwargs_from_options(options):
+ """
+ Given command line options, create dictionary suitable for passing to __init__
+ """
+ return modulation_utils.extract_kwargs_from_options(gmsk_mod.__init__,
+ ('self',), options)
+ extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
+
+
+
+# /////////////////////////////////////////////////////////////////////////////
+# GMSK demodulator
+# /////////////////////////////////////////////////////////////////////////////
+
+class gmsk_demod(gr.hier_block2):
+
+ def __init__(self,
+ samples_per_symbol=_def_samples_per_symbol,
+ gain_mu=_def_gain_mu,
+ mu=_def_mu,
+ omega_relative_limit=_def_omega_relative_limit,
+ freq_error=_def_freq_error,
+ verbose=_def_verbose,
+ log=_def_log):
+ """
+ Hierarchical block for Gaussian Minimum Shift Key (GMSK)
+ demodulation.
+
+ The input is the complex modulated signal at baseband.
+ The output is a stream of bits packed 1 bit per byte (the LSB)
+
+ @param samples_per_symbol: samples per baud
+ @type samples_per_symbol: integer
+ @param verbose: Print information about modulator?
+ @type verbose: bool
+ @param log: Print modualtion data to files?
+ @type log: bool
+
+ Clock recovery parameters. These all have reasonble defaults.
+
+ @param gain_mu: controls rate of mu adjustment
+ @type gain_mu: float
+ @param mu: fractional delay [0.0, 1.0]
+ @type mu: float
+ @param omega_relative_limit: sets max variation in omega
+ @type omega_relative_limit: float, typically 0.000200 (200 ppm)
+ @param freq_error: bit rate error as a fraction
+ @param float
+ """
+
+ gr.hier_block2.__init__(self, "gmsk_demod",
+ gr.io_signature(1, 1, gr.sizeof_gr_complex), # Input signature
+ gr.io_signature(1, 1, gr.sizeof_char)) # Output signature
+
+ self._samples_per_symbol = samples_per_symbol
+ self._gain_mu = gain_mu
+ self._mu = mu
+ self._omega_relative_limit = omega_relative_limit
+ self._freq_error = freq_error
+
+ if samples_per_symbol < 2:
+ raise TypeError, "samples_per_symbol >= 2, is %f" % samples_per_symbol
+
+ self._omega = samples_per_symbol*(1+self._freq_error)
+
+ if not self._gain_mu:
+ self._gain_mu = 0.175
+
+ self._gain_omega = .25 * self._gain_mu * self._gain_mu # critically damped
+
+ # Demodulate FM
+ sensitivity = (pi / 2) / samples_per_symbol
+ self.fmdemod = gr.quadrature_demod_cf(1.0 / sensitivity)
+
+ # the clock recovery block tracks the symbol clock and resamples as needed.
+ # the output of the block is a stream of soft symbols (float)
+ self.clock_recovery = gr.clock_recovery_mm_ff(self._omega, self._gain_omega,
+ self._mu, self._gain_mu,
+ self._omega_relative_limit)
+
+ # slice the floats at 0, outputting 1 bit (the LSB of the output byte) per sample
+ self.slicer = gr.binary_slicer_fb()
+
+ if verbose:
+ self._print_verbage()
+
+ if log:
+ self._setup_logging()
+
+ # Connect & Initialize base class
+ self.connect(self, self.fmdemod, self.clock_recovery, self.slicer, self)
+
+ def samples_per_symbol(self):
+ return self._samples_per_symbol
+
+ def bits_per_symbol(self=None): # staticmethod that's also callable on an instance
+ return 1
+ bits_per_symbol = staticmethod(bits_per_symbol) # make it a static method.
+
+
+ def _print_verbage(self):
+ print "bits per symbol = %d" % self.bits_per_symbol()
+ print "M&M clock recovery omega = %f" % self._omega
+ print "M&M clock recovery gain mu = %f" % self._gain_mu
+ print "M&M clock recovery mu = %f" % self._mu
+ print "M&M clock recovery omega rel. limit = %f" % self._omega_relative_limit
+ print "frequency error = %f" % self._freq_error
+
+
+ def _setup_logging(self):
+ print "Demodulation logging turned on."
+ self.connect(self.fmdemod,
+ gr.file_sink(gr.sizeof_float, "fmdemod.dat"))
+ self.connect(self.clock_recovery,
+ gr.file_sink(gr.sizeof_float, "clock_recovery.dat"))
+ self.connect(self.slicer,
+ gr.file_sink(gr.sizeof_char, "slicer.dat"))
+
+ def add_options(parser):
+ """
+ Adds GMSK demodulation-specific options to the standard parser
+ """
+ parser.add_option("", "--gain-mu", type="float", default=_def_gain_mu,
+ help="M&M clock recovery gain mu [default=%default] (GMSK/PSK)")
+ parser.add_option("", "--mu", type="float", default=_def_mu,
+ help="M&M clock recovery mu [default=%default] (GMSK/PSK)")
+ parser.add_option("", "--omega-relative-limit", type="float", default=_def_omega_relative_limit,
+ help="M&M clock recovery omega relative limit [default=%default] (GMSK/PSK)")
+ parser.add_option("", "--freq-error", type="float", default=_def_freq_error,
+ help="M&M clock recovery frequency error [default=%default] (GMSK)")
+ add_options=staticmethod(add_options)
+
+ def extract_kwargs_from_options(options):
+ """
+ Given command line options, create dictionary suitable for passing to __init__
+ """
+ return modulation_utils.extract_kwargs_from_options(gmsk_demod.__init__,
+ ('self',), options)
+ extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
+
+
+#
+# Add these to the mod/demod registry
+#
+modulation_utils.add_type_1_mod('gmsk', gmsk_mod)
+modulation_utils.add_type_1_demod('gmsk', gmsk_demod)
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