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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 2, 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 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 = 0.15
  43 _def_gain_mu = 0.1
  44 _def_mu = 0.5
  45 _def_omega_relative_limit = 0.005
  46
  47
  48 # /////////////////////////////////////////////////////////////////////////////
  49 #                             DBPSK modulator
  50 # /////////////////////////////////////////////////////////////////////////////
  51
  52 class dbpsk_mod(gr.hier_block2):
  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 components
 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     def samples_per_symbol(self):
 127         return self._samples_per_symbol
 128
 129     def bits_per_symbol(self=None):   # static method that's also callable on an instance
 130         return 1
 131     bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.  RTFM
 132
 133     def add_options(parser):
 134         """
 135         Adds DBPSK modulation-specific options to the standard parser
 136         """
 137         parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
 138                           help="set RRC excess bandwith factor [default=%default]")
 139         parser.add_option("", "--no-gray-code", dest="gray_code",
 140                           action="store_false", default=True,
 141                           help="disable gray coding on modulated bits (PSK)")
 142     add_options=staticmethod(add_options)
 143
 144     def extract_kwargs_from_options(options):
 145         """
 146         Given command line options, create dictionary suitable for passing to __init__
 147         """
 148         return modulation_utils.extract_kwargs_from_options(dbpsk_mod.__init__,
 149                                                             ('self', 'fg'), options)
 150     extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
 151
 152
 153     def _print_verbage(self):
 154         print "\nModulator:"
 155         print "bits per symbol = %d" % self.bits_per_symbol()
 156         print "Gray code = %s" % self._gray_code
 157         print "RRC roll-off factor = %.2f" % self._excess_bw
 158
 159     def _setup_logging(self):
 160         print "Modulation logging turned on."
 161         self.connect(self.bytes2chunks, gr.file_sink(gr.sizeof_char, "tx_bytes2chunks.dat"))
 162         self.connect(self.symbol_mapper, gr.file_sink(gr.sizeof_char, "tx_symbol_mapper.dat"))
 163         self.connect(self.diffenc, gr.file_sink(gr.sizeof_char, "tx_diffenc.dat"))
 164         self.connect(self.chunks2symbols, gr.file_sink(gr.sizeof_gr_complex, "tx_chunks2symbols.dat"))
 165         self.connect(self.rrc_filter, gr.file_sink(gr.sizeof_gr_complex, "tx_rrc_filter.dat"))
 166
 167
 168 # /////////////////////////////////////////////////////////////////////////////
 169 #                             DBPSK demodulator
 170 #
 171 #      Differentially coherent detection of differentially encoded BPSK
 172 # /////////////////////////////////////////////////////////////////////////////
 173
 174 class dbpsk_demod(gr.hier_block2):
 175
 176     def __init__(self,
 177                  samples_per_symbol=_def_samples_per_symbol,
 178                  excess_bw=_def_excess_bw,
 179                  costas_alpha=_def_costas_alpha,
 180                  gain_mu=_def_gain_mu,
 181                  mu=_def_mu,
 182                  omega_relative_limit=_def_omega_relative_limit,
 183                  gray_code=_def_gray_code,
 184                  verbose=_def_verbose,
 185                  log=_def_log):
 186         """
 187         Hierarchical block for RRC-filtered differential BPSK demodulation
 188
 189         The input is the complex modulated signal at baseband.
 190         The output is a stream of bits packed 1 bit per byte (LSB)
 191
 192         @param samples_per_symbol: samples per symbol >= 2
 193         @type samples_per_symbol: float
 194         @param excess_bw: Root-raised cosine filter excess bandwidth
 195         @type excess_bw: float
 196         @param costas_alpha: loop filter gain
 197         @type costas_alphas: float
 198         @param gain_mu: for M&M block
 199         @type gain_mu: float
 200         @param mu: for M&M block
 201         @type mu: float
 202         @param omega_relative_limit: for M&M block
 203         @type omega_relative_limit: float
 204         @param gray_code: Tell modulator to Gray code the bits
 205         @type gray_code: bool
 206         @param verbose: Print information about modulator?
 207         @type verbose: bool
 208         @param debug: Print modualtion data to files?
 209         @type debug: bool
 210         """
 211
 212         gr.hier_block2.__init__(self, "dbpsk_demod",
 213                                 gr.io_signature(1,1,gr.sizeof_gr_complex), # Input signature
 214                                 gr.io_signature(1,1,gr.sizeof_char))       # Output signature
 215
 216
 217         self._samples_per_symbol = samples_per_symbol
 218         self._excess_bw = excess_bw
 219         self._costas_alpha = costas_alpha
 220         self._mm_gain_mu = gain_mu
 221         self._mm_mu = mu
 222         self._mm_omega_relative_limit = omega_relative_limit
 223         self._gray_code = gray_code
 224
 225         if samples_per_symbol < 2:
 226             raise TypeError, "samples_per_symbol must be >= 2, is %r" % (samples_per_symbol,)
 227
 228         arity = pow(2,self.bits_per_symbol())
 229
 230         # Automatic gain control
 231         scale = (1.0/16384.0)
 232         self.pre_scaler = gr.multiply_const_cc(scale)   # scale the signal from full-range to +-1
 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
 237         # RRC data filter
 238         ntaps = 11 * samples_per_symbol
 239         self.rrc_taps = gr.firdes.root_raised_cosine(
 240             1.0,                      # gain
 241             self._samples_per_symbol, # sampling rate
 242             1.0,                      # symbol rate
 243             self._excess_bw,          # excess bandwidth (roll-off factor)
 244             ntaps)
 245         self.rrc_filter=gr.interp_fir_filter_ccf(1, self.rrc_taps)
 246
 247         # symbol clock recovery
 248         self._mm_omega = self._samples_per_symbol
 249         self._mm_gain_omega = .25 * self._mm_gain_mu * self._mm_gain_mu
 250         self._costas_beta  = 0.25 * self._costas_alpha * self._costas_alpha
 251         fmin = -0.02
 252         fmax = 0.02
 253
 254         self.receiver=gr.mpsk_receiver_cc(arity, 0,
 255                                           self._costas_alpha, self._costas_beta,
 256                                           fmin, fmax,
 257                                           self._mm_mu, self._mm_gain_mu,
 258                                           self._mm_omega, self._mm_gain_omega,
 259                                           self._mm_omega_relative_limit)
 260
 261         # Using differential decoding
 262         self.diffdec = gr.diff_phasor_cc()
 263
 264         # find closest constellation point
 265         rot = 1
 266         rotated_const = map(lambda pt: pt * rot, psk.constellation[arity])
 267         self.slicer = gr.constellation_decoder_cb(rotated_const, range(arity))
 268
 269         if self._gray_code:
 270             self.symbol_mapper = gr.map_bb(psk.gray_to_binary[arity])
 271         else:
 272             self.symbol_mapper = gr.map_bb(psk.ungray_to_binary[arity])
 273
 274         # unpack the k bit vector into a stream of bits
 275         self.unpack = gr.unpack_k_bits_bb(self.bits_per_symbol())
 276
 277         # Connect and Initialize base class
 278         self.connect(self, self.pre_scaler, self.agc, self.rrc_filter, self.receiver,
 279                      self.diffdec, self.slicer, self.symbol_mapper, self.unpack, self)
 280
 281         if verbose:
 282             self._print_verbage()
 283
 284         if log:
 285             self._setup_logging()
 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:   %.2e" % self._costas_alpha
 300         print "Costas Loop beta:    %.2e" % self._costas_beta
 301         print "M&M mu:              %.2f" % self._mm_mu
 302         print "M&M mu gain:         %.2e" % self._mm_gain_mu
 303         print "M&M omega:           %.2f" % self._mm_omega
 304         print "M&M omega gain:      %.2e" % self._mm_gain_omega
 305         print "M&M omega limit:     %.2f" % self._mm_omega_relative_limit
 306
 307     def _setup_logging(self):
 308         print "Demodulation logging turned on."
 309         self.connect(self.pre_scaler, gr.file_sink(gr.sizeof_gr_complex, "rx_prescaler.dat"))
 310         self.connect(self.agc, gr.file_sink(gr.sizeof_gr_complex, "rx_agc.dat"))
 311         self.connect(self.rrc_filter, gr.file_sink(gr.sizeof_gr_complex, "rx_rrc_filter.dat"))
 312         self.connect(self.receiver, gr.file_sink(gr.sizeof_gr_complex, "rx_receiver.dat"))
 313         self.connect(self.diffdec, gr.file_sink(gr.sizeof_gr_complex, "rx_diffdec.dat"))
 314         self.connect(self.slicer, gr.file_sink(gr.sizeof_char, "rx_slicer.dat"))
 315         self.connect(self.symbol_mapper, gr.file_sink(gr.sizeof_char, "rx_symbol_mapper.dat"))
 316         self.connect(self.unpack, gr.file_sink(gr.sizeof_char, "rx_unpack.dat"))
 317
 318     def add_options(parser):
 319         """
 320         Adds DBPSK demodulation-specific options to the standard parser
 321         """
 322         parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
 323                           help="set RRC excess bandwith factor [default=%default] (PSK)")
 324         parser.add_option("", "--no-gray-code", dest="gray_code",
 325                           action="store_false", default=_def_gray_code,
 326                           help="disable gray coding on modulated bits (PSK)")
 327         parser.add_option("", "--costas-alpha", type="float", default=None,
 328                           help="set Costas loop alpha value [default=%default] (PSK)")
 329         parser.add_option("", "--gain-mu", type="float", default=_def_gain_mu,
 330                           help="set M&M symbol sync loop gain mu value [default=%default] (GMSK/PSK)")
 331         parser.add_option("", "--mu", type="float", default=_def_mu,
 332                           help="set M&M symbol sync loop mu value [default=%default] (GMSK/PSK)")
 333         parser.add_option("", "--omega-relative-limit", type="float", default=_def_omega_relative_limit,
 334                           help="M&M clock recovery omega relative limit [default=%default] (GMSK/PSK)")
 335     add_options=staticmethod(add_options)
 336
 337     def extract_kwargs_from_options(options):
 338         """
 339         Given command line options, create dictionary suitable for passing to __init__
 340         """
 341         return modulation_utils.extract_kwargs_from_options(
 342                  dbpsk_demod.__init__, ('self'), options)
 343     extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
 344 #
 345 # Add these to the mod/demod registry
 346 #
 347 modulation_utils.add_type_1_mod('dbpsk', dbpsk_mod)
 348 modulation_utils.add_type_1_demod('dbpsk', dbpsk_demod)