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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 2, 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.hier_block2):
  34     def __init__(self, options):
  35         gr.hier_block2.__init__(self,
  36                                 "dect_receiver",        # Block typename
  37                                 gr.io_signature(0,0,0), # Input signature
  38                                 gr.io_signature(0,0,0)) # Output signature
  39         self._options = options
  40
  41         # Need greater than 2 samples per symbol. This makes a decimation
  42         # rate of 26 and a samples per symbol of 2.136752
  43         if_rate = 2.461538e6
  44         self._usrp = usrp_source_c(self,
  45                                    which=0,
  46                                    subdev_spec=options.rx_subdev_spec,
  47                                    if_rate=if_rate,
  48                                    gain=options.gain,
  49                                    freq=options.freq,
  50                                    calibration=options.calibration,
  51                                    verbose=options.verbose)
  52
  53         # Filter baseband to 1.186 MHz passband, 1.728 MHz stopband
  54         chan_taps = optfir.low_pass(1.0,              # Gain
  55                                     if_rate,          # Sample rate
  56                                     _dect_occupied_bandwidth/2, # One sided modulation bandwidth
  57                                     _dect_channel_bandwidth/2,  # One sided channel bandwidth
  58                                     1.0,              # Passband ripple (db)
  59                                     60)               # Stopband attenuation (db)
  60         if self._options.verbose:
  61             print "Channel filter has", len(chan_taps), "taps"
  62         self._channel_filter = gr.freq_xlating_fir_filter_ccf(1,         # Decimation rate
  63                                                               chan_taps, # Filter taps
  64                                                               0.0,       # Offset frequency
  65                                                               if_rate)   # Sample rate
  66
  67         self._demod = gmsk2_demod(samples_per_symbol=if_rate/_dect_symbol_rate,
  68                                   verbose=options.verbose)
  69
  70         # Define and connect components
  71         self.define_component("usrp", self._usrp)
  72         self.define_component("channel", self._channel_filter)
  73         self.define_component("demod", self._demod)
  74         self.define_component("sink", gr.null_sink(gr.sizeof_char))
  75         self.connect("usrp", 0, "channel", 0)
  76         self.connect("channel", 0, "demod", 0)
  77         self.connect("demod", 0, "sink", 0)
  78
  79         # Log baseband to file if requested
  80         if options.log_baseband is not None:
  81             if options.verbose:
  82                 print "Logging baseband to file", options.log_baseband
  83             self.define_component("baseband_log", gr.file_sink(gr.sizeof_gr_complex, options.log_baseband))
  84             self.connect("channel", 0, "baseband_log", 0)
  85
  86         # Log demodulator output to file if requested
  87         if options.log_demod is not None:
  88             if options.verbose:
  89                 print "Logging demodulator to file", options.log_demod
  90             self.define_component("demod_log", gr.file_sink(gr.sizeof_char, options.log_demod))
  91             self.connect("demod", 0, "demod_log", 0)