agc2.h

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/* -*- c++ -*- */
/*
 * Copyright 2006,2012 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 INCLUDED_ANALOG_AGC2_H
#define INCLUDED_ANALOG_AGC2_H

#include <analog/api.h>
#include <gr_complex.h>
#include <math.h>

namespace gr {
  namespace analog {
    namespace kernel {

      /*!
       * \brief high performance Automatic Gain Control class
       *
       * \details
       * For Power the absolute value of the complex number is used.
       */
      class ANALOG_API agc2_cc
      {
      public:
        agc2_cc(float attack_rate = 1e-1, float decay_rate = 1e-2,
                float reference = 1.0,
                float gain = 1.0, float max_gain = 0.0)
          : _attack_rate(attack_rate), _decay_rate(decay_rate),
          _reference(reference),
          _gain(gain), _max_gain(max_gain) {};

        float decay_rate() const  { return _decay_rate; }
        float attack_rate() const { return _attack_rate; }
        float reference() const   { return _reference; }
        float gain() const        { return _gain;  }
        float max_gain() const     { return _max_gain; }

        void set_decay_rate(float rate) { _decay_rate = rate; }
        void set_attack_rate(float rate) { _attack_rate = rate; }
        void set_reference(float reference) { _reference = reference; }
        void set_gain(float gain) { _gain = gain; }
        void set_max_gain(float max_gain) { _max_gain = max_gain; }

        gr_complex scale(gr_complex input)
        {
          gr_complex output = input * _gain;

          float tmp = -_reference + sqrt(output.real()*output.real() +
                                         output.imag()*output.imag());
          float rate = _decay_rate;
          if((tmp) > _gain) {
            rate = _attack_rate;
          }
          _gain -= tmp*rate;

          // Not sure about this; will blow up if _gain < 0 (happens
          // when rates are too high), but is this the solution?
          if(_gain < 0.0)
            _gain = 10e-5;

          if(_max_gain > 0.0 && _gain > _max_gain) {
            _gain = _max_gain;
          }
          return output;
        }

        void scaleN(gr_complex output[], const gr_complex input[], unsigned n)
        {
          for(unsigned i = 0; i < n; i++)
            output[i] = scale (input[i]);
        }

      protected:
        float _attack_rate;     // attack rate for fast changing signals
        float _decay_rate;      // decay rate for slow changing signals
        float _reference;       // reference value
        float _gain;            // current gain
        float _max_gain;        // max allowable gain
      };


      class ANALOG_API agc2_ff
      {
      public:
        agc2_ff(float attack_rate = 1e-1, float decay_rate = 1e-2,
                float reference = 1.0,
                float gain = 1.0, float max_gain = 0.0)
          : _attack_rate(attack_rate), _decay_rate(decay_rate),
          _reference(reference),
          _gain(gain), _max_gain(max_gain) {};

        float attack_rate() const { return _attack_rate; }
        float decay_rate() const  { return _decay_rate; }
        float reference() const   { return _reference; }
        float gain() const        { return _gain;  }
        float max_gain() const    { return _max_gain; }

        void set_attack_rate(float rate) { _attack_rate = rate; }
        void set_decay_rate(float rate) { _decay_rate = rate; }
        void set_reference(float reference) { _reference = reference; }
        void set_gain(float gain) { _gain = gain; }
        void set_max_gain(float max_gain) { _max_gain = max_gain; }

        float scale(float input)
        {
          float output = input * _gain;

          float tmp = (fabsf(output)) - _reference;
          float rate = _decay_rate;
          if(fabsf(tmp) > _gain) {
            rate = _attack_rate;
          }
          _gain -= tmp*rate;

          // Not sure about this
          if(_gain < 0.0)
            _gain = 10e-5;

          if(_max_gain > 0.0 && _gain > _max_gain) {
            _gain = _max_gain;
          }
          return output;
        }

        void scaleN(float output[], const float input[], unsigned n)
        {
          for(unsigned i = 0; i < n; i++)
            output[i] = scale (input[i]);
        }

      protected:
        float _attack_rate;     // attack_rate for fast changing signals
        float _decay_rate;      // decay rate for slow changing signals
        float _reference;       // reference value
        float _gain;            // current gain
        float _max_gain;        // maximum gain
      };
      
    } /* namespace kernel */
  } /* namespace analog */
} /* namespace gr */

#endif /* INCLUDED_ANALOG_AGC2_H */