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/* -*- c++ -*- */
/*
* Copyright 2002 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* GNU Radio is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3, or (at your option)
* any later version.
*
* GNU Radio is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GNU Radio; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#ifndef _ATSC_SLICER_AGC_H_
#define _ATSC_SLICER_AGC_H_
#include <atsc_api.h>
#include <math.h>
#include <gr_single_pole_iir.h>
/*!
* \brief Automatic Gain Control class for atsc slicer
*
* Given perfect data, output values will be +/- {7, 5, 3, 1}
*/
class ATSC_API atsci_slicer_agc {
public:
atsci_slicer_agc () : _gain(1), dc(0.0025) {};
float gain () { return _gain; }
#if 1
float scale (float input){
float t = input * _gain;
float output = t - REFERENCE;
float error = REFERENCE - dc.filter (t);
_gain += error * RATE;
return output;
}
#else
float scale(float input){
float avg = dc.filter(input);
if(fabs(avg)<.1)avg=.1;
_gain += _gain*.99 + .01* REFERENCE/avg;
return input*_gain - REFERENCE;
}
#endif
protected:
static const float REFERENCE = 1.25; // pilot reference value
static const float RATE = 1.0e-5; // adjustment rate
float _gain; // current gain
gr_single_pole_iir<float,float,float> dc;
};
#endif /* _ATSC_SLICER_AGC_H_ */
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