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   1 #
   2 # Copyright 2005,2006 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/gmsk2 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 import Numeric
  33 from pprint import pprint
  34
  35 # default values (used in __init__ and add_options)
  36 _def_samples_per_symbol = 2
  37 _def_excess_bw = 0.35
  38 _def_gray_code = True
  39 _def_verbose = False
  40 _def_log = False
  41
  42 _def_costas_alpha = None
  43 _def_gain_mu = 0.03
  44 _def_mu = 0.05
  45 _def_omega_relative_limit = 0.005
  46
  47
  48 # /////////////////////////////////////////////////////////////////////////////
  49 #                             DBPSK modulator
  50 # /////////////////////////////////////////////////////////////////////////////
  51
  52 class dbpsk_mod(gr.hier_block):
  53
  54     def __init__(self, fg,
  55                  samples_per_symbol=_def_samples_per_symbol,
  56                  excess_bw=_def_excess_bw,
  57                  gray_code=_def_gray_code,
  58                  verbose=_def_verbose,
  59                  log=_def_log):
  60         """
  61         Hierarchical block for RRC-filtered differential BPSK modulation.
  62
  63         The input is a byte stream (unsigned char) and the
  64         output is the complex modulated signal at baseband.
  65
  66         @param fg: flow graph
  67         @type fg: flow graph
  68         @param samples_per_symbol: samples per baud >= 2
  69         @type samples_per_symbol: integer
  70         @param excess_bw: Root-raised cosine filter excess bandwidth
  71         @type excess_bw: float
  72         @param gray_code: Tell modulator to Gray code the bits
  73         @type gray_code: bool
  74         @param verbose: Print information about modulator?
  75         @type verbose: bool
  76         @param log: Log modulation data to files?
  77         @type log: bool
  78         """
  79
  80         self._fg = fg
  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
 114         self.rrc_filter = gr.interp_fir_filter_ccf(self._samples_per_symbol,
 115                                                    self.rrc_taps)
 116
 117         # Connect
 118         fg.connect(self.bytes2chunks, self.symbol_mapper, self.diffenc,
 119                    self.chunks2symbols, self.rrc_filter)
 120
 121         if verbose:
 122             self._print_verbage()
 123
 124         if log:
 125             self._setup_logging()
 126
 127         # Initialize base class
 128         gr.hier_block.__init__(self, self._fg, self.bytes2chunks, self.rrc_filter)
 129
 130     def samples_per_symbol(self):
 131         return self._samples_per_symbol
 132
 133     def bits_per_symbol(self=None):   # static method that's also callable on an instance
 134         return 1
 135     bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.  RTFM
 136
 137     def add_options(parser):
 138         """
 139         Adds DBPSK modulation-specific options to the standard parser
 140         """
 141         parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
 142                           help="set RRC excess bandwith factor [default=%default]")
 143         parser.add_option("", "--no-gray-code", dest="gray_code",
 144                           action="store_false", default=True,
 145                           help="disable gray coding on modulated bits (PSK)")
 146     add_options=staticmethod(add_options)
 147
 148     def extract_kwargs_from_options(options):
 149         """
 150         Given command line options, create dictionary suitable for passing to __init__
 151         """
 152         return modulation_utils.extract_kwargs_from_options(dbpsk_mod.__init__,
 153                                                             ('self', 'fg'), options)
 154     extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
 155
 156
 157     def _print_verbage(self):
 158         print "bits per symbol = %d" % self.bits_per_symbol()
 159         print "Gray code = %s" % self._gray_code
 160         print "RRC roll-off factor = %.2f" % self._excess_bw
 161
 162     def _setup_logging(self):
 163         print "Modulation logging turned on."
 164         self._fg.connect(self.bytes2chunks,
 165                          gr.file_sink(gr.sizeof_char, "bytes2chunks.dat"))
 166         self._fg.connect(self.symbol_mapper,
 167                          gr.file_sink(gr.sizeof_char, "graycoder.dat"))
 168         self._fg.connect(self.diffenc,
 169                          gr.file_sink(gr.sizeof_char, "diffenc.dat"))
 170         self._fg.connect(self.chunks2symbols,
 171                          gr.file_sink(gr.sizeof_gr_complex, "chunks2symbols.dat"))
 172         self._fg.connect(self.rrc_filter,
 173                          gr.file_sink(gr.sizeof_gr_complex, "rrc_filter.dat"))
 174
 175
 176 # /////////////////////////////////////////////////////////////////////////////
 177 #                             DBPSK demodulator
 178 #
 179 #      Differentially coherent detection of differentially encoded BPSK
 180 # /////////////////////////////////////////////////////////////////////////////
 181
 182 class dbpsk_demod(gr.hier_block):
 183
 184     def __init__(self, fg,
 185                  samples_per_symbol=_def_samples_per_symbol,
 186                  excess_bw=_def_excess_bw,
 187                  costas_alpha=_def_costas_alpha,
 188                  gain_mu=_def_gain_mu,
 189                  mu=_def_mu,
 190                  omega_relative_limit=_def_omega_relative_limit,
 191                  gray_code=_def_gray_code,
 192                  verbose=_def_verbose,
 193                  log=_def_log):
 194         """
 195         Hierarchical block for RRC-filtered differential BPSK demodulation
 196
 197         The input is the complex modulated signal at baseband.
 198         The output is a stream of bits packed 1 bit per byte (LSB)
 199
 200         @param fg: flow graph
 201         @type fg: flow graph
 202         @param samples_per_symbol: samples per symbol >= 2
 203         @type samples_per_symbol: float
 204         @param excess_bw: Root-raised cosine filter excess bandwidth
 205         @type excess_bw: float
 206         @param costas_alpha: loop filter gain
 207         @type costas_alphas: float
 208         @param gain_mu: for M&M block
 209         @type gain_mu: float
 210         @param mu: for M&M block
 211         @type mu: float
 212         @param omega_relative_limit: for M&M block
 213         @type omega_relative_limit: float
 214         @param gray_code: Tell modulator to Gray code the bits
 215         @type gray_code: bool
 216         @param verbose: Print information about modulator?
 217         @type verbose: bool
 218         @param debug: Print modualtion data to files?
 219         @type debug: bool
 220         """
 221
 222         self._fg = fg
 223         self._samples_per_symbol = samples_per_symbol
 224         self._excess_bw = excess_bw
 225         self._costas_alpha = costas_alpha
 226         self._gain_mu = gain_mu
 227         self._mu = mu
 228         self._omega_relative_limit = omega_relative_limit
 229         self._gray_code = gray_code
 230
 231         if samples_per_symbol < 2:
 232             raise TypeError, "samples_per_symbol must be >= 2, is %r" % (samples_per_symbol,)
 233
 234         arity = pow(2,self.bits_per_symbol())
 235
 236         # Automatic gain control
 237         scale = (1.0/16384.0)
 238         self.pre_scaler = gr.multiply_const_cc(scale)   # scale the signal from full-range to +-1
 239         #self.agc = gr.agc2_cc(0.6e-1, 1e-3, 1, 1, 100)
 240         self.agc = gr.feedforward_agc_cc(16, 1.0)
 241
 242
 243         # Costas loop (carrier tracking)
 244         # The Costas loop is not needed for BPSK, though it can help. Turn the Costas loop on
 245         # by setting an alpha value not None.
 246         if self._costas_alpha is not None:
 247             costas_order = 2
 248             beta = .25 * self._costas_alpha * self._costas_alpha
 249             self.costas_loop = gr.costas_loop_cc(self._costas_alpha, beta, 0.002, -0.002, costas_order)
 250
 251         # RRC data filter
 252         ntaps = 11 * self._samples_per_symbol
 253         self.rrc_taps = gr.firdes.root_raised_cosine(
 254             1.0,                      # gain
 255             self._samples_per_symbol, # sampling rate
 256             1.0,                      # symbol rate
 257             self._excess_bw,          # excess bandwidth (roll-off factor)
 258             ntaps)
 259
 260         self.rrc_filter=gr.fir_filter_ccf(1, self.rrc_taps)
 261
 262         # symbol clock recovery
 263         omega = self._samples_per_symbol
 264         gain_omega = .25 * self._gain_mu * self._gain_mu
 265         self.clock_recovery=gr.clock_recovery_mm_cc(omega, gain_omega,
 266                                                     self._mu, self._gain_mu,
 267                                                     self._omega_relative_limit)
 268
 269         # find closest constellation point
 270         rot = 1
 271         rotated_const = map(lambda pt: pt * rot, psk.constellation[arity])
 272         #print "rotated_const =", rotated_const
 273
 274         self.diffdec = gr.diff_phasor_cc()
 275         #self.diffdec = gr.diff_decoder_bb(arity)
 276
 277         self.slicer = gr.constellation_decoder_cb(rotated_const, range(arity))
 278
 279         if self._gray_code:
 280             self.symbol_mapper = gr.map_bb(psk.gray_to_binary[arity])
 281         else:
 282             self.symbol_mapper = gr.map_bb(psk.ungray_to_binary[arity])
 283
 284         # unpack the k bit vector into a stream of bits
 285         self.unpack = gr.unpack_k_bits_bb(self.bits_per_symbol())
 286
 287         if verbose:
 288             self._print_verbage()
 289
 290         if log:
 291             self._setup_logging()
 292
 293         # Connect and Initialize base class
 294         if self._costas_alpha is not None:   # With Costas Loop
 295             self._fg.connect(self.pre_scaler, self.agc, self.costas_loop,
 296                              self.rrc_filter, self.clock_recovery, self.diffdec,
 297                              self.slicer, self.symbol_mapper, self.unpack)
 298         else: # Without Costas Loop
 299             self._fg.connect(self.pre_scaler, self.agc,
 300                              self.rrc_filter, self.clock_recovery, self.diffdec,
 301                              self.slicer, self.symbol_mapper, self.unpack)
 302
 303         gr.hier_block.__init__(self, self._fg, self.pre_scaler, self.unpack)
 304
 305     def samples_per_symbol(self):
 306         return self._samples_per_symbol
 307
 308     def bits_per_symbol(self=None):   # staticmethod that's also callable on an instance
 309         return 1
 310     bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.  RTFM
 311
 312     def _print_verbage(self):
 313         print "bits per symbol = %d"         % self.bits_per_symbol()
 314         print "Gray code = %s"               % self._gray_code
 315         print "RRC roll-off factor = %.2f"   % self._excess_bw
 316         if self._costas_alpha is not None:
 317             print "Costas Loop alpha = %.5f"     % self._costas_alpha
 318         else:
 319             print "Costas Loop is turned off"
 320         print "M&M symbol sync gain = %.5f"  % self._gain_mu
 321         print "M&M symbol sync mu = %.5f"    % self._mu
 322         print "M&M omega relative limit = %.5f" % self._omega_relative_limit
 323
 324     def _setup_logging(self):
 325         print "Modulation logging turned on."
 326         self._fg.connect(self.pre_scaler,
 327                          gr.file_sink(gr.sizeof_gr_complex, "prescaler.dat"))
 328         self._fg.connect(self.agc,
 329                          gr.file_sink(gr.sizeof_gr_complex, "agc.dat"))
 330         if self._costas_alpha is not None:
 331             self._fg.connect(self.costas_loop,
 332                              gr.file_sink(gr.sizeof_gr_complex, "costas_loop.dat"))
 333             self._fg.connect((self.costas_loop,1),
 334                              gr.file_sink(gr.sizeof_gr_complex, "costas_error.dat"))
 335         self._fg.connect(self.rrc_filter,
 336                          gr.file_sink(gr.sizeof_gr_complex, "rrc_filter.dat"))
 337         self._fg.connect(self.clock_recovery,
 338                          gr.file_sink(gr.sizeof_gr_complex, "clock_recovery.dat"))
 339         self._fg.connect((self.clock_recovery,1),
 340                          gr.file_sink(gr.sizeof_gr_complex, "clock_recovery_error.dat"))
 341         self._fg.connect(self.diffdec,
 342                          gr.file_sink(gr.sizeof_gr_complex, "diffdec.dat"))
 343         self._fg.connect(self.slicer,
 344                         gr.file_sink(gr.sizeof_char, "slicer.dat"))
 345         self._fg.connect(self.symbol_mapper,
 346                          gr.file_sink(gr.sizeof_char, "symbol_mapper.dat"))
 347         self._fg.connect(self.unpack,
 348                          gr.file_sink(gr.sizeof_char, "unpack.dat"))
 349
 350     def add_options(parser):
 351         """
 352         Adds DBPSK demodulation-specific options to the standard parser
 353         """
 354         parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
 355                           help="set RRC excess bandwith factor [default=%default] (PSK)")
 356         parser.add_option("", "--no-gray-code", dest="gray_code",
 357                           action="store_false", default=_def_gray_code,
 358                           help="disable gray coding on modulated bits (PSK)")
 359         parser.add_option("", "--costas-alpha", type="float", default=None,
 360                           help="set Costas loop alpha value [default=%default] (PSK)")
 361         parser.add_option("", "--gain-mu", type="float", default=_def_gain_mu,
 362                           help="set M&M symbol sync loop gain mu value [default=%default] (GMSK/PSK)")
 363         parser.add_option("", "--mu", type="float", default=_def_mu,
 364                           help="set M&M symbol sync loop mu value [default=%default] (GMSK/PSK)")
 365         parser.add_option("", "--omega-relative-limit", type="float", default=_def_omega_relative_limit,
 366                           help="M&M clock recovery omega relative limit [default=%default] (GMSK/PSK)")
 367     add_options=staticmethod(add_options)
 368
 369     def extract_kwargs_from_options(options):
 370         """
 371         Given command line options, create dictionary suitable for passing to __init__
 372         """
 373         return modulation_utils.extract_kwargs_from_options(
 374                  dbpsk_demod.__init__, ('self', 'fg'), options)
 375     extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
 376
 377 #
 378 # Add these to the mod/demod registry
 379 #
 380 modulation_utils.add_type_1_mod('dbpsk', dbpsk_mod)
 381 modulation_utils.add_type_1_demod('dbpsk', dbpsk_demod)