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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_utils2
  29 from math import pi, sqrt, ceil
  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_freq_alpha = 0.010
  42 _def_phase_alpha = 0.1
  43 _def_timing_alpha = 0.100
  44 _def_timing_beta = 0.010
  45 _def_timing_max_dev = 1.5
  46
  47
  48 # /////////////////////////////////////////////////////////////////////////////
  49 #                             DBPSK modulator
  50 # /////////////////////////////////////////////////////////////////////////////
  51
  52 class dbpsk2_mod(gr.hier_block2):
  53
  54     def __init__(self,
  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 samples_per_symbol: samples per baud >= 2
  67         @type samples_per_symbol: integer
  68         @param excess_bw: Root-raised cosine filter excess bandwidth
  69         @type excess_bw: float
  70         @param gray_code: Tell modulator to Gray code the bits
  71         @type gray_code: bool
  72         @param verbose: Print information about modulator?
  73         @type verbose: bool
  74         @param log: Log modulation data to files?
  75         @type log: bool
  76         """
  77
  78         gr.hier_block2.__init__(self, "dbpsk_mod",
  79                                 gr.io_signature(1, 1, gr.sizeof_char),       # Input signature
  80                                 gr.io_signature(1, 1, gr.sizeof_gr_complex)) # Output signature
  81
  82         self._samples_per_symbol = samples_per_symbol
  83         self._excess_bw = excess_bw
  84         self._gray_code = gray_code
  85
  86         if self._samples_per_symbol < 2:
  87             raise TypeError, ("sbp must be an integer >= 2, is %d" % self._samples_per_symbol)
  88
  89         arity = pow(2,self.bits_per_symbol())
  90
  91         # turn bytes into k-bit vectors
  92         self.bytes2chunks = \
  93           gr.packed_to_unpacked_bb(self.bits_per_symbol(), gr.GR_MSB_FIRST)
  94
  95         if self._gray_code:
  96             self.symbol_mapper = gr.map_bb(psk.binary_to_gray[arity])
  97         else:
  98             self.symbol_mapper = gr.map_bb(psk.binary_to_ungray[arity])
  99
 100         self.diffenc = gr.diff_encoder_bb(arity)
 101
 102         self.chunks2symbols = gr.chunks_to_symbols_bc(psk.constellation[arity])
 103
 104         # pulse shaping filter
 105         nfilts = 32
 106         ntaps = nfilts * 11 * int(self._samples_per_symbol)    # make nfilts filters of ntaps each
 107         self.rrc_taps = gr.firdes.root_raised_cosine(
 108             nfilts,          # gain
 109             nfilts,          # sampling rate based on 32 filters in resampler
 110             1.0,             # symbol rate
 111             self._excess_bw, # excess bandwidth (roll-off factor)
 112             ntaps)
 113         self.rrc_filter = gr.pfb_arb_resampler_ccf(self._samples_per_symbol, self.rrc_taps)
 114
 115         # Connect
 116         self.connect(self, self.bytes2chunks, self.symbol_mapper, self.diffenc,
 117                      self.chunks2symbols, self.rrc_filter, self)
 118
 119         if verbose:
 120             self._print_verbage()
 121
 122         if log:
 123             self._setup_logging()
 124
 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_utils2.extract_kwargs_from_options(dbpsk2_mod.__init__,
 149                                                             ('self',), 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,
 162                      gr.file_sink(gr.sizeof_char, "tx_bytes2chunks.dat"))
 163         self.connect(self.symbol_mapper,
 164                      gr.file_sink(gr.sizeof_char, "tx_graycoder.dat"))
 165         self.connect(self.diffenc,
 166                      gr.file_sink(gr.sizeof_char, "tx_diffenc.dat"))
 167         self.connect(self.chunks2symbols,
 168                      gr.file_sink(gr.sizeof_gr_complex, "tx_chunks2symbols.dat"))
 169         self.connect(self.rrc_filter,
 170                      gr.file_sink(gr.sizeof_gr_complex, "tx_rrc_filter.dat"))
 171
 172
 173 # /////////////////////////////////////////////////////////////////////////////
 174 #                             DBPSK demodulator
 175 #
 176 #      Differentially coherent detection of differentially encoded BPSK
 177 # /////////////////////////////////////////////////////////////////////////////
 178
 179 class dbpsk2_demod(gr.hier_block2):
 180
 181     def __init__(self,
 182                  samples_per_symbol=_def_samples_per_symbol,
 183                  excess_bw=_def_excess_bw,
 184                  freq_alpha=_def_freq_alpha,
 185                  phase_alpha=_def_phase_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                  sync_out=False):
 192         """
 193         Hierarchical block for RRC-filtered differential BPSK demodulation
 194
 195         The input is the complex modulated signal at baseband.
 196         The output is a stream of bits packed 1 bit per byte (LSB)
 197
 198         @param samples_per_symbol: samples per symbol >= 2
 199         @type samples_per_symbol: float
 200         @param excess_bw: Root-raised cosine filter excess bandwidth
 201         @type excess_bw: float
 202         @param freq_alpha: loop filter gain for frequency recovery
 203         @type freq_alpha: float
 204         @param phase_alpha: loop filter gain for phase/fine frequency recovery
 205         @type phase_alpha: float
 206         @param timing_alpha: loop alpha gain for timing recovery
 207         @type timing_alpha: float
 208         @param timing_max: timing loop maximum rate deviations
 209         @type timing_max: float
 210         @param gray_code: Tell modulator to Gray code the bits
 211         @type gray_code: bool
 212         @param verbose: Print information about modulator?
 213         @type verbose: bool
 214         @param log: Print modualtion data to files?
 215         @type log: bool
 216         @param sync_out: Output a sync signal on :1?
 217         @type sync_out: bool
 218         """
 219         if sync_out: io_sig_out = gr.io_signaturev(2, 2, (gr.sizeof_char, gr.sizeof_gr_complex))
 220         else: io_sig_out = gr.io_signature(1, 1, gr.sizeof_char)
 221
 222         gr.hier_block2.__init__(self, "dqpsk2_demod",
 223                                 gr.io_signature(1, 1, gr.sizeof_gr_complex), # Input signature
 224                                 io_sig_out)       # Output signature
 225
 226         self._samples_per_symbol = samples_per_symbol
 227         self._excess_bw = excess_bw
 228         self._freq_alpha = freq_alpha
 229         self._freq_beta = 0.10*self._freq_alpha
 230         self._phase_alpha = phase_alpha
 231         self._timing_alpha = timing_alpha
 232         self._timing_beta = _def_timing_beta
 233         self._timing_max_dev=timing_max_dev
 234         self._gray_code = gray_code
 235
 236         if samples_per_symbol < 2:
 237             raise TypeError, "samples_per_symbol must be >= 2, is %r" % (samples_per_symbol,)
 238
 239         arity = pow(2,self.bits_per_symbol())
 240
 241         # Automatic gain control
 242         self.agc = gr.agc2_cc(0.6e-1, 1e-3, 1, 1, 100)
 243         #self.agc = gr.feedforward_agc_cc(16, 1.0)
 244
 245         # Frequency correction
 246         self.freq_recov = gr.fll_band_edge_cc(self._samples_per_symbol, self._excess_bw,
 247                                               11*int(self._samples_per_symbol),
 248                                               self._freq_alpha, self._freq_beta)
 249
 250         # symbol timing recovery with RRC data filter
 251         nfilts = 32
 252         ntaps = 11 * int(self._samples_per_symbol*nfilts)
 253         taps = gr.firdes.root_raised_cosine(nfilts, nfilts,
 254                                             1.0/float(self._samples_per_symbol),
 255                                             self._excess_bw, ntaps)
 256         self.time_recov = gr.pfb_clock_sync_ccf(self._samples_per_symbol,
 257                                                 self._timing_alpha,
 258                                                 taps, nfilts, nfilts/2, self._timing_max_dev)
 259         self.time_recov.set_beta(self._timing_beta)
 260
 261         # Perform phase / fine frequency correction
 262         self._phase_beta  = 0.25 * self._phase_alpha * self._phase_alpha
 263         # Allow a frequency swing of +/- half of the sample rate
 264         fmin = -0.5
 265         fmax = 0.5
 266
 267         self.phase_recov = gr.costas_loop_cc(self._phase_alpha,
 268                                              self._phase_beta,
 269                                              fmax, fmin, arity)
 270
 271         # Do differential decoding based on phase change of symbols
 272         self.diffdec = gr.diff_phasor_cc()
 273
 274         # find closest constellation point
 275         rot = 1
 276         rotated_const = map(lambda pt: pt * rot, psk.constellation[arity])
 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
 294         self.connect(self, self.agc,
 295                      self.freq_recov, self.time_recov, self.phase_recov,
 296                      self.diffdec, self.slicer, self.symbol_mapper, self.unpack, self)
 297         if sync_out: self.connect(self.time_recov, (self, 1))
 298
 299     def samples_per_symbol(self):
 300         return self._samples_per_symbol
 301
 302     def bits_per_symbol(self=None):   # staticmethod that's also callable on an instance
 303         return 1
 304     bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.  RTFM
 305
 306     def _print_verbage(self):
 307         print "\nDemodulator:"
 308         print "bits per symbol:     %d"   % self.bits_per_symbol()
 309         print "Gray code:           %s"   % self._gray_code
 310         print "RRC roll-off factor: %.2f" % self._excess_bw
 311         print "FLL gain:            %.2e" % self._freq_alpha
 312         print "Timing alpha gain:   %.2e" % self._timing_alpha
 313         print "Timing beta gain:    %.2e" % self._timing_beta
 314         print "Timing max dev:      %.2f" % self._timing_max_dev
 315         print "Phase track alpha:   %.2e" % self._phase_alpha
 316         print "Phase track beta:    %.2e" % self._phase_beta
 317
 318     def _setup_logging(self):
 319         print "Modulation logging turned on."
 320         self.connect(self.agc,
 321                      gr.file_sink(gr.sizeof_gr_complex, "rx_agc.dat"))
 322         self.connect(self.freq_recov,
 323                      gr.file_sink(gr.sizeof_gr_complex, "rx_freq_recov.dat"))
 324         self.connect(self.time_recov,
 325                      gr.file_sink(gr.sizeof_gr_complex, "rx_time_recov.dat"))
 326         self.connect(self.phase_recov,
 327                      gr.file_sink(gr.sizeof_gr_complex, "rx_phase_recov.dat"))
 328         self.connect(self.diffdec,
 329                      gr.file_sink(gr.sizeof_gr_complex, "rx_diffdec.dat"))
 330         self.connect(self.slicer,
 331                      gr.file_sink(gr.sizeof_char, "rx_slicer.dat"))
 332         self.connect(self.symbol_mapper,
 333                      gr.file_sink(gr.sizeof_char, "rx_symbol_mapper.dat"))
 334         self.connect(self.unpack,
 335                      gr.file_sink(gr.sizeof_char, "rx_unpack.dat"))
 336
 337     def add_options(parser):
 338         """
 339         Adds DBPSK demodulation-specific options to the standard parser
 340         """
 341         parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
 342                           help="set RRC excess bandwith factor [default=%default] (PSK)")
 343         parser.add_option("", "--no-gray-code", dest="gray_code",
 344                           action="store_false", default=_def_gray_code,
 345                           help="disable gray coding on modulated bits (PSK)")
 346         parser.add_option("", "--freq-alpha", type="float", default=_def_freq_alpha,
 347                           help="set frequency lock loop alpha gain value [default=%default] (PSK)")
 348         parser.add_option("", "--phase-alpha", type="float", default=_def_phase_alpha,
 349                           help="set phase tracking loop alpha value [default=%default] (PSK)")
 350         parser.add_option("", "--timing-alpha", type="float", default=_def_timing_alpha,
 351                           help="set timing symbol sync loop gain alpha value [default=%default] (GMSK/PSK)")
 352         parser.add_option("", "--timing-beta", type="float", default=_def_timing_beta,
 353                           help="set timing symbol sync loop gain beta value [default=%default] (GMSK/PSK)")
 354         parser.add_option("", "--timing-max-dev", type="float", default=_def_timing_max_dev,
 355                           help="set timing symbol sync loop maximum deviation [default=%default] (GMSK/PSK)")
 356     add_options=staticmethod(add_options)
 357
 358     def extract_kwargs_from_options(options):
 359         """
 360         Given command line options, create dictionary suitable for passing to __init__
 361         """
 362         return modulation_utils2.extract_kwargs_from_options(
 363                  dbpsk2_demod.__init__, ('self',), options)
 364     extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
 365 #
 366 # Add these to the mod/demod registry
 367 #
 368 modulation_utils2.add_type_1_mod('dbpsk2', dbpsk2_mod)
 369 modulation_utils2.add_type_1_demod('dbpsk2', dbpsk2_demod)