2 # GMSK modulation and demodulation.
5 # Copyright 2005,2006 Free Software Foundation, Inc.
7 # This file is part of GNU Radio
9 # GNU Radio is free software; you can redistribute it and/or modify
10 # it under the terms of the GNU General Public License as published by
11 # the Free Software Foundation; either version 2, or (at your option)
14 # GNU Radio is distributed in the hope that it will be useful,
15 # but WITHOUT ANY WARRANTY; without even the implied warranty of
16 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 # GNU General Public License for more details.
19 # You should have received a copy of the GNU General Public License
20 # along with GNU Radio; see the file COPYING. If not, write to
21 # the Free Software Foundation, Inc., 51 Franklin Street,
22 # Boston, MA 02110-1301, USA.
25 # See gnuradio-examples/python/digital for examples
27 from gnuradio import gr
28 from gnuradio import modulation_utils
31 from pprint import pprint
34 # default values (used in __init__ and add_options)
35 _def_samples_per_symbol = 2
43 _def_omega_relative_limit = 0.005
46 # /////////////////////////////////////////////////////////////////////////////
48 # /////////////////////////////////////////////////////////////////////////////
50 class gmsk_mod(gr.hier_block2):
53 samples_per_symbol=_def_samples_per_symbol,
58 Hierarchical block for Gaussian Minimum Shift Key (GMSK)
61 The input is a byte stream (unsigned char) and the
62 output is the complex modulated signal at baseband.
64 @param samples_per_symbol: samples per baud >= 2
65 @type samples_per_symbol: integer
66 @param bt: Gaussian filter bandwidth * symbol time
68 @param verbose: Print information about modulator?
70 @param debug: Print modualtion data to files?
74 gr.hier_block2.__init__(self, "gmsk_mod",
75 gr.io_signature(1,1,gr.sizeof_char), # Input signature
76 gr.io_signature(1,1,gr.sizeof_gr_complex)) # Output signature
78 self._samples_per_symbol = samples_per_symbol
81 if not isinstance(samples_per_symbol, int) or samples_per_symbol < 2:
82 raise TypeError, ("samples_per_symbol must be an integer >= 2, is %r" % (samples_per_symbol,))
84 ntaps = 4 * samples_per_symbol # up to 3 bits in filter at once
85 sensitivity = (pi / 2) / samples_per_symbol # phase change per bit = pi / 2
87 # Turn it into NRZ data.
88 self.nrz = gr.bytes_to_syms()
90 # Form Gaussian filter
91 # Generate Gaussian response (Needs to be convolved with window below).
92 self.gaussian_taps = gr.firdes.gaussian(
94 samples_per_symbol, # symbol_rate
95 bt, # bandwidth * symbol time
96 ntaps # number of taps
99 self.sqwave = (1,) * samples_per_symbol # rectangular window
100 self.taps = Numeric.convolve(Numeric.array(self.gaussian_taps),Numeric.array(self.sqwave))
101 self.gaussian_filter = gr.interp_fir_filter_fff(samples_per_symbol, self.taps)
104 self.fmmod = gr.frequency_modulator_fc(sensitivity)
106 # Define components from objects
107 self.define_component("nrz", self.nrz)
108 self.define_component("gaussian_filter", self.gaussian_filter)
109 self.define_component("fmmod", self.fmmod)
112 self.connect("self", 0, "nrz", 0)
113 self.connect("nrz", 0, "gaussian_filter", 0)
114 self.connect("gaussian_filter", 0, "fmmod", 0)
115 self.connect("fmmod", 0, "self", 0)
118 self._print_verbage()
121 self._setup_logging()
123 def samples_per_symbol(self):
124 return self._samples_per_symbol
126 def bits_per_symbol(self=None): # staticmethod that's also callable on an instance
128 bits_per_symbol = staticmethod(bits_per_symbol) # make it a static method.
131 def _print_verbage(self):
132 print "bits per symbol = %d" % self.bits_per_symbol()
133 print "Gaussian filter bt = %.2f" % self._bt
136 def _setup_logging(self):
137 print "Modulation logging turned on."
138 self.define_component("nrz_dat", gr.file_sink(gr.sizeof_float, "tx_nrz.dat"))
139 self.define_component("gaussian_filter_dat", gr.file_sink(gr.sizeof_float, "tx_gaussian_filter.dat"))
140 self.define_component("fmmod_dat", gr.file_sink(gr.sizeof_gr_complex, "tx_fmmod.dat"))
142 self.connect("nrz", 0, "nrz_dat", 0)
143 self.connect("gaussian_filter", 0, "gaussian_filter_dat", 0)
144 self.connect("fmmod", 0, "fmmod_dat", 0)
146 def add_options(parser):
148 Adds GMSK modulation-specific options to the standard parser
150 parser.add_option("", "--bt", type="float", default=_def_bt,
151 help="set bandwidth-time product [default=%default] (GMSK)")
152 add_options=staticmethod(add_options)
155 def extract_kwargs_from_options(options):
157 Given command line options, create dictionary suitable for passing to __init__
159 return modulation_utils.extract_kwargs_from_options(gmsk_mod.__init__,
160 ('self', 'fg'), options)
161 extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
165 # /////////////////////////////////////////////////////////////////////////////
167 # /////////////////////////////////////////////////////////////////////////////
169 class gmsk_demod(gr.hier_block2):
172 samples_per_symbol=_def_samples_per_symbol,
173 gain_mu=_def_gain_mu,
175 omega_relative_limit=_def_omega_relative_limit,
176 freq_error=_def_freq_error,
177 verbose=_def_verbose,
180 Hierarchical block for Gaussian Minimum Shift Key (GMSK)
183 The input is the complex modulated signal at baseband.
184 The output is a stream of bits packed 1 bit per byte (the LSB)
186 @param samples_per_symbol: samples per baud
187 @type samples_per_symbol: integer
188 @param verbose: Print information about modulator?
190 @param log: Print modualtion data to files?
193 Clock recovery parameters. These all have reasonble defaults.
195 @param gain_mu: controls rate of mu adjustment
197 @param mu: fractional delay [0.0, 1.0]
199 @param omega_relative_limit: sets max variation in omega
200 @type omega_relative_limit: float, typically 0.000200 (200 ppm)
201 @param freq_error: bit rate error as a fraction
205 gr.hier_block2.__init__(self, "gmsk_demod",
206 gr.io_signature(1,1,gr.sizeof_gr_complex), # Input signature
207 gr.io_signature(1,1,gr.sizeof_char)) # Output signature
209 self._samples_per_symbol = samples_per_symbol
210 self._gain_mu = gain_mu
212 self._omega_relative_limit = omega_relative_limit
213 self._freq_error = freq_error
215 if samples_per_symbol < 2:
216 raise TypeError, "samples_per_symbol >= 2, is %f" % samples_per_symbol
218 self._omega = samples_per_symbol*(1+self._freq_error)
220 self._gain_omega = .25 * self._gain_mu * self._gain_mu # critically damped
223 sensitivity = (pi / 2) / samples_per_symbol
224 self.fmdemod = gr.quadrature_demod_cf(1.0 / sensitivity)
226 # the clock recovery block tracks the symbol clock and resamples as needed.
227 # the output of the block is a stream of soft symbols (float)
228 self.clock_recovery = gr.clock_recovery_mm_ff(self._omega, self._gain_omega,
229 self._mu, self._gain_mu,
230 self._omega_relative_limit)
232 # slice the floats at 0, outputting 1 bit (the LSB of the output byte) per sample
233 self.slicer = gr.binary_slicer_fb()
235 # Define components from objects
236 self.define_component("fmdemod", self.fmdemod)
237 self.define_component("clock_recovery", self.clock_recovery)
238 self.define_component("slicer", self.slicer)
241 self.connect("self", 0, "fmdemod", 0)
242 self.connect("fmdemod", 0, "clock_recovery", 0)
243 self.connect("clock_recovery", 0, "slicer", 0)
244 self.connect("slicer", 0, "self", 0)
247 self._print_verbage()
250 self._setup_logging()
252 def samples_per_symbol(self):
253 return self._samples_per_symbol
255 def bits_per_symbol(self=None): # staticmethod that's also callable on an instance
257 bits_per_symbol = staticmethod(bits_per_symbol) # make it a static method.
259 def _print_verbage(self):
260 print "bits per symbol = %d" % self.bits_per_symbol()
261 print "M&M clock recovery omega = %f" % self._omega
262 print "M&M clock recovery gain mu = %f" % self._gain_mu
263 print "M&M clock recovery mu = %f" % self._mu
264 print "M&M clock recovery omega rel. limit = %f" % self._omega_relative_limit
265 print "frequency error = %f" % self._freq_error
268 def _setup_logging(self):
269 print "Demodulation logging turned on."
270 self.define_component("fmdemod_dat", gr.file_sink(gr.sizeof_float, "rx_fmdemod.dat"))
271 self.define_component("clock_recovery_dat", gr.file_sink(gr.sizeof_float, "rx_clock_recovery.dat"))
272 self.define_component("slicer_dat", gr.file_sink(gr.sizeof_char, "rx_slicer.dat"))
274 self.connect("fmdemod", 0, "fmdemod_dat", 0)
275 self.connect("clock_recovery", 0, "clock_recovery_dat", 0)
276 self.connect("slicer", 0, "slicer_dat", 0)
278 def add_options(parser):
280 Adds GMSK demodulation-specific options to the standard parser
282 parser.add_option("", "--gain-mu", type="float", default=_def_gain_mu,
283 help="M&M clock recovery gain mu [default=%default] (GMSK/PSK)")
284 parser.add_option("", "--mu", type="float", default=_def_mu,
285 help="M&M clock recovery mu [default=%default] (GMSK/PSK)")
286 parser.add_option("", "--omega-relative-limit", type="float", default=_def_omega_relative_limit,
287 help="M&M clock recovery omega relative limit [default=%default] (GMSK/PSK)")
288 parser.add_option("", "--freq-error", type="float", default=_def_freq_error,
289 help="M&M clock recovery frequency error [default=%default] (GMSK)")
290 add_options=staticmethod(add_options)
292 def extract_kwargs_from_options(options):
294 Given command line options, create dictionary suitable for passing to __init__
296 return modulation_utils.extract_kwargs_from_options(gmsk_demod.__init__,
297 ('self', 'fg'), options)
298 extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
302 # Add these to the mod/demod registry
304 modulation_utils.add_type_1_mod('gmsk', gmsk_mod)
305 modulation_utils.add_type_1_demod('gmsk', gmsk_demod)