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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 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 QPSK modulation and demodulation.
  26 """
  27
  28 from gnuradio import gr, gru, modulation_utils
  29 from math import pi, sqrt
  30 import qam
  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 #                           QAM64 modulator
  50 # /////////////////////////////////////////////////////////////////////////////
  51
  52 class qam64_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         """
  62         Hierarchical block for RRC-filtered QPSK modulation.
  63
  64         The input is a byte stream (unsigned char) and the
  65         output is the complex modulated signal at baseband.
  66
  67         @param fg: flow graph
  68         @type fg: flow graph
  69         @param samples_per_symbol: samples per symbol >= 2
  70         @type samples_per_symbol: integer
  71         @param excess_bw: Root-raised cosine filter excess bandwidth
  72         @type excess_bw: float
  73         @param gray_code: Tell modulator to Gray code the bits
  74         @type gray_code: bool
  75         @param verbose: Print information about modulator?
  76         @type verbose: bool
  77         @param debug: Print modualtion data to files?
  78         @type debug: bool
  79         """
  80
  81         self._fg = fg
  82         self._samples_per_symbol = samples_per_symbol
  83         self._excess_bw = excess_bw
  84         self._gray_code = gray_code
  85
  86         if not isinstance(samples_per_symbol, int) or samples_per_symbol < 2:
  87             raise TypeError, ("sbp must be an integer >= 2, is %d" % samples_per_symbol)
  88
  89         ntaps = 11 * samples_per_symbol
  90
  91         arity = pow(2, self.bits_per_symbol())
  92
  93         # turn bytes into k-bit vectors
  94         self.bytes2chunks = \
  95           gr.packed_to_unpacked_bb(self.bits_per_symbol(), gr.GR_MSB_FIRST)
  96
  97         if self._gray_code:
  98             self.symbol_mapper = gr.map_bb(qam.binary_to_gray[arity])
  99         else:
 100             self.symbol_mapper = gr.map_bb(qam.binary_to_ungray[arity])
 101
 102         self.diffenc = gr.diff_encoder_bb(arity)
 103
 104         rot = 1.0
 105         print "constellation with %d arity" % arity
 106         rotated_const = map(lambda pt: pt * rot, qam.constellation[arity])
 107         self.chunks2symbols = gr.chunks_to_symbols_bc(rotated_const)
 108
 109         # pulse shaping filter
 110         self.rrc_taps = gr.firdes.root_raised_cosine(
 111             self._samples_per_symbol, # gain  (sps since we're interpolating by sps)
 112             self._samples_per_symbol, # sampling rate
 113             1.0,                      # symbol rate
 114             self._excess_bw,          # excess bandwidth (roll-off factor)
 115             ntaps)
 116
 117         self.rrc_filter = gr.interp_fir_filter_ccf(self._samples_per_symbol, self.rrc_taps)
 118
 119         if verbose:
 120             self._print_verbage()
 121
 122         if log:
 123             self._setup_logging()
 124
 125         # Connect & Initialize base class
 126         self._fg.connect(self.bytes2chunks, self.symbol_mapper, self.diffenc,
 127                          self.chunks2symbols, self.rrc_filter)
 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):   # staticmethod that's also callable on an instance
 134         return 6
 135     bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.  RTFM
 136
 137     def _print_verbage(self):
 138         print "bits per symbol = %d" % self.bits_per_symbol()
 139         print "Gray code = %s" % self._gray_code
 140         print "RRS roll-off factor = %f" % self._excess_bw
 141
 142     def _setup_logging(self):
 143         print "Modulation logging turned on."
 144         self._fg.connect(self.bytes2chunks,
 145                          gr.file_sink(gr.sizeof_char, "bytes2chunks.dat"))
 146         self._fg.connect(self.symbol_mapper,
 147                          gr.file_sink(gr.sizeof_char, "graycoder.dat"))
 148         self._fg.connect(self.diffenc,
 149                          gr.file_sink(gr.sizeof_char, "diffenc.dat"))
 150         self._fg.connect(self.chunks2symbols,
 151                          gr.file_sink(gr.sizeof_gr_complex, "chunks2symbols.dat"))
 152         self._fg.connect(self.rrc_filter,
 153                          gr.file_sink(gr.sizeof_gr_complex, "rrc_filter.dat"))
 154
 155     def add_options(parser):
 156         """
 157         Adds QAM modulation-specific options to the standard parser
 158         """
 159         parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
 160                           help="set RRC excess bandwith factor [default=%default] (PSK)")
 161         parser.add_option("", "--no-gray-code", dest="gray_code",
 162                           action="store_false", default=_def_gray_code,
 163                           help="disable gray coding on modulated bits (PSK)")
 164     add_options=staticmethod(add_options)
 165
 166
 167     def extract_kwargs_from_options(options):
 168         """
 169         Given command line options, create dictionary suitable for passing to __init__
 170         """
 171         return modulation_utils.extract_kwargs_from_options(qam64_mod.__init__,
 172                                                             ('self', 'fg'), options)
 173     extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
 174
 175
 176 # /////////////////////////////////////////////////////////////////////////////
 177 #                           QAM16 demodulator
 178 #
 179 # /////////////////////////////////////////////////////////////////////////////
 180
 181 class qam64_demod(gr.hier_block):
 182
 183     def __init__(self, fg,
 184                  samples_per_symbol=_def_samples_per_symbol,
 185                  excess_bw=_def_excess_bw,
 186                  costas_alpha=_def_costas_alpha,
 187                  gain_mu=_def_gain_mu,
 188                  mu=_def_mu,
 189                  omega_relative_limit=_def_omega_relative_limit,
 190                  gray_code=_def_gray_code,
 191                  verbose=_def_verbose,
 192                  log=_def_log):
 193
 194         # do this
 195         pass
 196
 197     def bits_per_symbol(self=None):   # staticmethod that's also callable on an instance
 198         return 6
 199     bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.  RTFM
 200
 201 #
 202 # Add these to the mod/demod registry
 203 #
 204 # NOT READY TO BE USED YET -- ENABLE AT YOUR OWN RISK
 205 #modulation_utils.add_type_1_mod('qam64', qam64_mod)
 206 #modulation_utils.add_type_1_demod('qam16', qam16_demod)