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Diffstat (limited to 'gr-digital/python/gfsk.py')
| -rw-r--r-- | gr-digital/python/gfsk.py | 306 |
1 files changed, 306 insertions, 0 deletions
diff --git a/gr-digital/python/gfsk.py b/gr-digital/python/gfsk.py new file mode 100644 index 000000000..c85fdf0e0 --- /dev/null +++ b/gr-digital/python/gfsk.py @@ -0,0 +1,306 @@ +# +# GFSK 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 +import modulation_utils +import digital_swig as digital +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_sensitivity = 1 +_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 + + +# FIXME: Figure out how to make GFSK work with pfb_arb_resampler_fff for both +# transmit and receive so we don't require integer samples per symbol. + + +# ///////////////////////////////////////////////////////////////////////////// +# GFSK modulator +# ///////////////////////////////////////////////////////////////////////////// + +class gfsk_mod(gr.hier_block2): + + def __init__(self, + samples_per_symbol=_def_samples_per_symbol, + sensitivity=_def_sensitivity, + bt=_def_bt, + verbose=_def_verbose, + log=_def_log): + """ + Hierarchical block for Gaussian Frequency Shift Key (GFSK) + 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, "gfsk_mod", + gr.io_signature(1, 1, gr.sizeof_char), # Input signature + gr.io_signature(1, 1, gr.sizeof_gr_complex)) # Output signature + + samples_per_symbol = int(samples_per_symbol) + self._samples_per_symbol = samples_per_symbol + self._bt = bt + self._differential = False + + 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( + 1.0, # 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) + + # small amount of output attenuation to prevent clipping USRP sink + self.amp = gr.multiply_const_cc(0.999) + + 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.amp, 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 GFSK modulation-specific options to the standard parser + """ + parser.add_option("", "--bt", type="float", default=_def_bt, + help="set bandwidth-time product [default=%default] (GFSK)") + 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(gfsk_mod.__init__, + ('self',), options) + extract_kwargs_from_options=staticmethod(extract_kwargs_from_options) + + + +# ///////////////////////////////////////////////////////////////////////////// +# GFSK demodulator +# ///////////////////////////////////////////////////////////////////////////// + +class gfsk_demod(gr.hier_block2): + + def __init__(self, + samples_per_symbol=_def_samples_per_symbol, + sensitivity=_def_sensitivity, + 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 (GFSK) + 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, "gfsk_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 + self._differential = False + + 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 = digital.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 = digital.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 GFSK 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] (GFSK/PSK)") + parser.add_option("", "--mu", type="float", default=_def_mu, + help="M&M clock recovery mu [default=%default] (GFSK/PSK)") + parser.add_option("", "--omega-relative-limit", type="float", default=_def_omega_relative_limit, + help="M&M clock recovery omega relative limit [default=%default] (GFSK/PSK)") + parser.add_option("", "--freq-error", type="float", default=_def_freq_error, + help="M&M clock recovery frequency error [default=%default] (GFSK)") + 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(gfsk_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('gfsk', gfsk_mod) +modulation_utils.add_type_1_demod('gfsk', gfsk_demod) |