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   1 #
   2 # Copyright 2005,2006,2007 Free Software Foundation, Inc.
   3 #
   4 # This file is part of GNU Radio
   5 #
   6 # GNU Radio is free software; you can redistribute it and/or modify
   7 # it under the terms of the GNU General Public License as published by
   8 # the Free Software Foundation; either version 3, or (at your option)
   9 # any later version.
  10 #
  11 # GNU Radio is distributed in the hope that it will be useful,
  12 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 # GNU General Public License for more details.
  15 #
  16 # You should have received a copy of the GNU General Public License
  17 # along with GNU Radio; see the file COPYING.  If not, write to
  18 # the Free Software Foundation, Inc., 51 Franklin Street,
  19 # Boston, MA 02110-1301, USA.
  20 #
  21
  22 # See gnuradio-examples/python/digital for examples
  23
  24 """
  25 differential BPSK modulation and demodulation.
  26 """
  27
  28 from gnuradio import gr, gru, modulation_utils
  29 from math import pi, sqrt
  30 import psk
  31 import cmath
  32 from pprint import pprint
  33
  34 # default values (used in __init__ and add_options)
  35 _def_samples_per_symbol = 2
  36 _def_excess_bw = 0.35
  37 _def_gray_code = True
  38 _def_verbose = False
  39 _def_log = False
  40
  41 _def_costas_alpha = 0.1
  42 _def_timing_alpha = None
  43 _def_timing_beta = None
  44 _def_timing_max_dev = 1.5
  45
  46
  47 # /////////////////////////////////////////////////////////////////////////////
  48 #                             DBPSK modulator
  49 # /////////////////////////////////////////////////////////////////////////////
  50
  51 class dbpsk2_mod(gr.hier_block2):
  52
  53     def __init__(self,
  54                  samples_per_symbol=_def_samples_per_symbol,
  55                  excess_bw=_def_excess_bw,
  56                  gray_code=_def_gray_code,
  57                  verbose=_def_verbose,
  58                  log=_def_log):
  59         """
  60         Hierarchical block for RRC-filtered differential BPSK modulation.
  61
  62         The input is a byte stream (unsigned char) and the
  63         output is the complex modulated signal at baseband.
  64
  65         @param samples_per_symbol: samples per baud >= 2
  66         @type samples_per_symbol: integer
  67         @param excess_bw: Root-raised cosine filter excess bandwidth
  68         @type excess_bw: float
  69         @param gray_code: Tell modulator to Gray code the bits
  70         @type gray_code: bool
  71         @param verbose: Print information about modulator?
  72         @type verbose: bool
  73         @param log: Log modulation data to files?
  74         @type log: bool
  75         """
  76
  77         gr.hier_block2.__init__(self, "dbpsk_mod",
  78                                 gr.io_signature(1, 1, gr.sizeof_char),       # Input signature
  79                                 gr.io_signature(1, 1, gr.sizeof_gr_complex)) # Output signature
  80
  81         self._samples_per_symbol = samples_per_symbol
  82         self._excess_bw = excess_bw
  83         self._gray_code = gray_code
  84
  85         if not isinstance(self._samples_per_symbol, int) or self._samples_per_symbol < 2:
  86             raise TypeError, ("sbp must be an integer >= 2, is %d" % self._samples_per_symbol)
  87
  88         ntaps = 11 * self._samples_per_symbol
  89
  90         arity = pow(2,self.bits_per_symbol())
  91
  92         # turn bytes into k-bit vectors
  93         self.bytes2chunks = \
  94           gr.packed_to_unpacked_bb(self.bits_per_symbol(), gr.GR_MSB_FIRST)
  95
  96         if self._gray_code:
  97             self.symbol_mapper = gr.map_bb(psk.binary_to_gray[arity])
  98         else:
  99             self.symbol_mapper = gr.map_bb(psk.binary_to_ungray[arity])
 100
 101         self.diffenc = gr.diff_encoder_bb(arity)
 102
 103         self.chunks2symbols = gr.chunks_to_symbols_bc(psk.constellation[arity])
 104
 105         # pulse shaping filter
 106         self.rrc_taps = gr.firdes.root_raised_cosine(
 107             self._samples_per_symbol,   # gain (samples_per_symbol since we're
 108                                         # interpolating by samples_per_symbol)
 109             self._samples_per_symbol,   # sampling rate
 110             1.0,                        # symbol rate
 111             self._excess_bw,            # excess bandwidth (roll-off factor)
 112             ntaps)
 113         self.rrc_filter = gr.interp_fir_filter_ccf(self._samples_per_symbol,
 114                                                    self.rrc_taps)
 115
 116         # Connect
 117         self.connect(self, self.bytes2chunks, self.symbol_mapper, self.diffenc,
 118                      self.chunks2symbols, self.rrc_filter, self)
 119
 120         if verbose:
 121             self._print_verbage()
 122
 123         if log:
 124             self._setup_logging()
 125
 126
 127     def samples_per_symbol(self):
 128         return self._samples_per_symbol
 129
 130     def bits_per_symbol(self=None):   # static method that's also callable on an instance
 131         return 1
 132     bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.  RTFM
 133
 134     def add_options(parser):
 135         """
 136         Adds DBPSK modulation-specific options to the standard parser
 137         """
 138         parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
 139                           help="set RRC excess bandwith factor [default=%default]")
 140         parser.add_option("", "--no-gray-code", dest="gray_code",
 141                           action="store_false", default=True,
 142                           help="disable gray coding on modulated bits (PSK)")
 143     add_options=staticmethod(add_options)
 144
 145     def extract_kwargs_from_options(options):
 146         """
 147         Given command line options, create dictionary suitable for passing to __init__
 148         """
 149         return modulation_utils.extract_kwargs_from_options(dbpsk2_mod.__init__,
 150                                                             ('self',), options)
 151     extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
 152
 153
 154     def _print_verbage(self):
 155         print "\nModulator:"
 156         print "bits per symbol:     %d" % self.bits_per_symbol()
 157         print "Gray code:           %s" % self._gray_code
 158         print "RRC roll-off factor: %.2f" % self._excess_bw
 159
 160     def _setup_logging(self):
 161         print "Modulation logging turned on."
 162         self.connect(self.bytes2chunks,
 163                      gr.file_sink(gr.sizeof_char, "tx_bytes2chunks.dat"))
 164         self.connect(self.symbol_mapper,
 165                      gr.file_sink(gr.sizeof_char, "tx_graycoder.dat"))
 166         self.connect(self.diffenc,
 167                      gr.file_sink(gr.sizeof_char, "tx_diffenc.dat"))
 168         self.connect(self.chunks2symbols,
 169                      gr.file_sink(gr.sizeof_gr_complex, "tx_chunks2symbols.dat"))
 170         self.connect(self.rrc_filter,
 171                      gr.file_sink(gr.sizeof_gr_complex, "tx_rrc_filter.dat"))
 172
 173
 174 # /////////////////////////////////////////////////////////////////////////////
 175 #                             DBPSK demodulator
 176 #
 177 #      Differentially coherent detection of differentially encoded BPSK
 178 # /////////////////////////////////////////////////////////////////////////////
 179
 180 class dbpsk2_demod(gr.hier_block2):
 181
 182     def __init__(self,
 183                  samples_per_symbol=_def_samples_per_symbol,
 184                  excess_bw=_def_excess_bw,
 185                  costas_alpha=_def_costas_alpha,
 186                  timing_alpha=_def_timing_alpha,
 187                  timing_max_dev=_def_timing_max_dev,
 188                  gray_code=_def_gray_code,
 189                  verbose=_def_verbose,
 190                  log=_def_log):
 191         """
 192         Hierarchical block for RRC-filtered differential BPSK demodulation
 193
 194         The input is the complex modulated signal at baseband.
 195         The output is a stream of bits packed 1 bit per byte (LSB)
 196
 197         @param samples_per_symbol: samples per symbol >= 2
 198         @type samples_per_symbol: float
 199         @param excess_bw: Root-raised cosine filter excess bandwidth
 200         @type excess_bw: float
 201         @param costas_alpha: loop filter gain
 202         @type costas_alpha: float
 203         @param timing_alpha: timing loop alpha gain
 204         @type timing_alpha: float
 205         @param timing_max: timing loop maximum rate deviations
 206         @type timing_max: float
 207         @param gray_code: Tell modulator to Gray code the bits
 208         @type gray_code: bool
 209         @param verbose: Print information about modulator?
 210         @type verbose: bool
 211         @param debug: Print modualtion data to files?
 212         @type debug: bool
 213         """
 214
 215         gr.hier_block2.__init__(self, "dbpsk2_demod",
 216                                 gr.io_signature(1, 1, gr.sizeof_gr_complex), # Input signature
 217                                 gr.io_signature(1, 1, gr.sizeof_char))       # Output signature
 218
 219         self._samples_per_symbol = samples_per_symbol
 220         self._excess_bw = excess_bw
 221         self._costas_alpha = costas_alpha
 222         self._timing_alpha = timing_alpha
 223         self._timing_beta = _def_timing_alpha
 224         self._timing_max_dev=timing_max_dev
 225         self._gray_code = gray_code
 226
 227         if samples_per_symbol < 2:
 228             raise TypeError, "samples_per_symbol must be >= 2, is %r" % (samples_per_symbol,)
 229
 230         arity = pow(2,self.bits_per_symbol())
 231
 232         # Automatic gain control
 233         self.agc = gr.agc2_cc(0.6e-1, 1e-3, 1, 1, 100)
 234         #self.agc = gr.feedforward_agc_cc(16, 1.0)
 235
 236         self._costas_beta  = 0.25 * self._costas_alpha * self._costas_alpha
 237         # Allow a frequency swing of +/- half of the sample rate
 238         fmin = -0.5
 239         fmax = 0.5
 240
 241         self.clock_recov = gr.costas_loop_cc(self._costas_alpha,
 242                                              self._costas_beta,
 243                                              fmax, fmin, arity)
 244
 245         # symbol clock recovery
 246         if not self._timing_alpha:
 247             self._timing_alpha = 2
 248             self._timing_beta = 0.020
 249
 250         # RRC data filter
 251         nfilts = 32
 252         ntaps = 11 * samples_per_symbol*nfilts
 253         taps = gr.firdes.root_raised_cosine(nfilts, nfilts, 1.0/float(self._samples_per_symbol), self._excess_bw, ntaps)
 254         self.time_recov = gr.pfb_clock_sync_ccf(self._samples_per_symbol,
 255                                                 self._timing_alpha,
 256                                                 taps, nfilts, nfilts/2, self._timing_max_dev)
 257         self.time_recov.set_beta(self._timing_beta)
 258
 259         # Do differential decoding based on phase change of symbols
 260         self.diffdec = gr.diff_phasor_cc()
 261
 262         # find closest constellation point
 263         rot = 1
 264         rotated_const = map(lambda pt: pt * rot, psk.constellation[arity])
 265         self.slicer = gr.constellation_decoder_cb(rotated_const, range(arity))
 266
 267         if self._gray_code:
 268             self.symbol_mapper = gr.map_bb(psk.gray_to_binary[arity])
 269         else:
 270             self.symbol_mapper = gr.map_bb(psk.ungray_to_binary[arity])
 271
 272         # unpack the k bit vector into a stream of bits
 273         self.unpack = gr.unpack_k_bits_bb(self.bits_per_symbol())
 274
 275         if verbose:
 276             self._print_verbage()
 277
 278         if log:
 279             self._setup_logging()
 280
 281         # Connect
 282         self.connect(self, self.agc,
 283                      self.clock_recov,
 284                      self.time_recov,
 285                      self.diffdec, self.slicer, self.symbol_mapper, self.unpack, self)
 286
 287     def samples_per_symbol(self):
 288         return self._samples_per_symbol
 289
 290     def bits_per_symbol(self=None):   # staticmethod that's also callable on an instance
 291         return 1
 292     bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.  RTFM
 293
 294     def _print_verbage(self):
 295         print "\nDemodulator:"
 296         print "bits per symbol:     %d"   % self.bits_per_symbol()
 297         print "Gray code:           %s"   % self._gray_code
 298         print "RRC roll-off factor: %.2f" % self._excess_bw
 299         print "Costas Loop alpha:   %.2f" % self._costas_alpha
 300         print "Costas Loop beta:    %.2f" % self._costas_beta
 301         print "Timing alpha gain:   %.2f" % self._timing_alpha
 302         print "Timing beta gain:    %.2f" % self._timing_beta
 303         print "Timing max dev:      %.2f" % self._timing_max_dev
 304
 305     def _setup_logging(self):
 306         print "Modulation logging turned on."
 307         self.connect(self.pre_scaler,
 308                          gr.file_sink(gr.sizeof_gr_complex, "rx_prescaler.dat"))
 309         self.connect(self.agc,
 310                      gr.file_sink(gr.sizeof_gr_complex, "rx_agc.dat"))
 311         self.connect(self.rrc_filter,
 312                      gr.file_sink(gr.sizeof_gr_complex, "rx_rrc_filter.dat"))
 313         self.connect(self.clock_recov,
 314                      gr.file_sink(gr.sizeof_gr_complex, "rx_clock_recov.dat"))
 315         self.connect(self.time_recov,
 316                      gr.file_sink(gr.sizeof_gr_complex, "rx_time_recov.dat"))
 317         self.connect(self.diffdec,
 318                      gr.file_sink(gr.sizeof_gr_complex, "rx_diffdec.dat"))
 319         self.connect(self.slicer,
 320                     gr.file_sink(gr.sizeof_char, "rx_slicer.dat"))
 321         self.connect(self.symbol_mapper,
 322                      gr.file_sink(gr.sizeof_char, "rx_symbol_mapper.dat"))
 323         self.connect(self.unpack,
 324                      gr.file_sink(gr.sizeof_char, "rx_unpack.dat"))
 325
 326     def add_options(parser):
 327         """
 328         Adds DBPSK demodulation-specific options to the standard parser
 329         """
 330         parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
 331                           help="set RRC excess bandwith factor [default=%default] (PSK)")
 332         parser.add_option("", "--no-gray-code", dest="gray_code",
 333                           action="store_false", default=_def_gray_code,
 334                           help="disable gray coding on modulated bits (PSK)")
 335         parser.add_option("", "--costas-alpha", type="float", default=None,
 336                           help="set Costas loop alpha value [default=%default] (PSK)")
 337         parser.add_option("", "--gain-alpha", type="float", default=_def_timing_alpha,
 338                           help="set timing symbol sync loop gain alpha value [default=%default] (GMSK/PSK)")
 339         parser.add_option("", "--gain-beta", type="float", default=_def_timing_beta,
 340                           help="set timing symbol sync loop gain beta value [default=%default] (GMSK/PSK)")
 341         parser.add_option("", "--timing-max-dev", type="float", default=_def_timing_max_dev,
 342                           help="set timing symbol sync loop maximum deviation [default=%default] (GMSK/PSK)")
 343     add_options=staticmethod(add_options)
 344
 345     def extract_kwargs_from_options(options):
 346         """
 347         Given command line options, create dictionary suitable for passing to __init__
 348         """
 349         return modulation_utils.extract_kwargs_from_options(
 350                  dbpsk2_demod.__init__, ('self',), options)
 351     extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
 352 #
 353 # Add these to the mod/demod registry
 354 #
 355 modulation_utils.add_type_1_mod('dbpsk2', dbpsk2_mod)
 356 modulation_utils.add_type_1_demod('dbpsk2', dbpsk2_demod)