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   1 #!/usr/bin/env python
   2 #
   3 # Copyright 2007 Free Software Foundation, Inc.
   4 #
   5 # This file is part of GNU Radio
   6 #
   7 # GNU Radio is free software; you can redistribute it and/or modify
   8 # it under the terms of the GNU General Public License as published by
   9 # the Free Software Foundation; either version 3, or (at your option)
  10 # any later version.
  11 #
  12 # GNU Radio is distributed in the hope that it will be useful,
  13 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 # GNU General Public License for more details.
  16 #
  17 # You should have received a copy of the GNU General Public License
  18 # along with GNU Radio; see the file COPYING.  If not, write to
  19 # the Free Software Foundation, Inc., 51 Franklin Street,
  20 # Boston, MA 02110-1301, USA.
  21 #
  22
  23 from gnuradio import gr, optfir
  24 from usrp_source import usrp_source_c
  25 from gmsk2 import gmsk2_demod
  26
  27 _dect_symbol_rate = 1.152e6
  28 _dect_occupied_bandwidth = _dect_symbol_rate * 1.03 # BT=0.5
  29 _dect_channel_bandwidth = 1.728e6
  30
  31 # Top-level hierarchical block that implements DECT demodulation and
  32 # decoding.
  33 class dect_receiver(gr.top_block):
  34     def __init__(self, options):
  35         gr.top_block.__init__(self, "dect_receiver")
  36         self._options = options
  37
  38         # Need greater than 2 samples per symbol. This makes a decimation
  39         # rate of 26 and a samples per symbol of 2.136752
  40         if_rate = 2.461538e6
  41         self._usrp = usrp_source_c(which=0,
  42                                    subdev_spec=options.rx_subdev_spec,
  43                                    if_rate=if_rate,
  44                                    gain=options.gain,
  45                                    freq=options.freq,
  46                                    calibration=options.calibration,
  47                                    verbose=options.verbose)
  48
  49         # Filter baseband to 1.186 MHz passband, 1.728 MHz stopband
  50         chan_taps = optfir.low_pass(1.0,              # Gain
  51                                     if_rate,          # Sample rate
  52                                     _dect_occupied_bandwidth/2, # One sided modulation bandwidth
  53                                     _dect_channel_bandwidth/2,  # One sided channel bandwidth
  54                                     1.0,              # Passband ripple (db)
  55                                     60)               # Stopband attenuation (db)
  56         if self._options.verbose:
  57             print "Channel filter has", len(chan_taps), "taps"
  58         self._channel_filter = gr.freq_xlating_fir_filter_ccf(1,         # Decimation rate
  59                                                               chan_taps, # Filter taps
  60                                                               0.0,       # Offset frequency
  61                                                               if_rate)   # Sample rate
  62
  63         self._demod = gmsk2_demod(samples_per_symbol=if_rate/_dect_symbol_rate,
  64                                   verbose=options.verbose)
  65
  66         self._sink = gr.null_sink(gr.sizeof_char)
  67         self.connect(self._usrp, self._channel_filter, self._demod, self._sink)
  68
  69         # Log baseband to file if requested
  70         if options.log_baseband is not None:
  71             if options.verbose:
  72                 print "Logging baseband to file", options.log_baseband
  73             self.baseband_log = gr.file_sink(gr.sizeof_gr_complex, options.log_baseband)
  74             self.connect(self._channel_filter, self.baseband_log)
  75
  76         # Log demodulator output to file if requested
  77         if options.log_demod is not None:
  78             if options.verbose:
  79                 print "Logging demodulator to file", options.log_demod
  80             self.demod_log = gr.file_sink(gr.sizeof_char, options.log_demod)
  81             self.connect(self._demod, self.demod_log)