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   1 #
   2 # Copyright 2005,2007 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 import math
  23 from gnuradio import gr, optfir
  24
  25 class standard_squelch(gr.hier_block2):
  26     def __init__(self, audio_rate):
  27         gr.hier_block2.__init__(self, "standard_squelch",
  28                                 gr.io_signature(1, 1, gr.sizeof_float), # Input signature
  29                                 gr.io_signature(1, 1, gr.sizeof_float)) # Output signature
  30
  31         self.input_node = gr.add_const_ff(0)          # FIXME kludge
  32
  33         self.low_iir = gr.iir_filter_ffd((0.0193,0,-0.0193),(1,1.9524,-0.9615))
  34         self.low_square = gr.multiply_ff()
  35         self.low_smooth = gr.single_pole_iir_filter_ff(1/(0.01*audio_rate))   # 100ms time constant
  36
  37         self.hi_iir = gr.iir_filter_ffd((0.0193,0,-0.0193),(1,1.3597,-0.9615))
  38         self.hi_square = gr.multiply_ff()
  39         self.hi_smooth = gr.single_pole_iir_filter_ff(1/(0.01*audio_rate))
  40
  41         self.sub = gr.sub_ff();
  42         self.add = gr.add_ff();
  43         self.gate = gr.threshold_ff(0.3,0.43,0)
  44         self.squelch_lpf = gr.single_pole_iir_filter_ff(1/(0.01*audio_rate))
  45
  46         self.div = gr.divide_ff()
  47         self.squelch_mult = gr.multiply_ff()
  48
  49         self.connect (self, self.input_node)
  50         self.connect (self.input_node, (self.squelch_mult, 0))
  51
  52         self.connect (self.input_node,self.low_iir)
  53         self.connect (self.low_iir,(self.low_square,0))
  54         self.connect (self.low_iir,(self.low_square,1))
  55         self.connect (self.low_square,self.low_smooth,(self.sub,0))
  56         self.connect (self.low_smooth, (self.add,0))
  57
  58         self.connect (self.input_node,self.hi_iir)
  59         self.connect (self.hi_iir,(self.hi_square,0))
  60         self.connect (self.hi_iir,(self.hi_square,1))
  61         self.connect (self.hi_square,self.hi_smooth,(self.sub,1))
  62         self.connect (self.hi_smooth, (self.add,1))
  63
  64         self.connect (self.sub, (self.div, 0))
  65         self.connect (self.add, (self.div, 1))
  66         self.connect (self.div, self.gate, self.squelch_lpf, (self.squelch_mult,1))
  67         self.connect (self.squelch_mult, self)
  68
  69     def set_threshold(self, threshold):
  70         self.gate.set_hi(threshold)
  71
  72     def threshold(self):
  73         return self.gate.hi()
  74
  75     def squelch_range(self):
  76         return (0.0, 1.0, 1.0/100)