GNU Radio 3.5.1 C++ API
gri_agc2_cc.h
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00001 /* -*- c++ -*- */
00002 /*
00003  * Copyright 2006 Free Software Foundation, Inc.
00004  * 
00005  * This file is part of GNU Radio
00006  * 
00007  * GNU Radio is free software; you can redistribute it and/or modify
00008  * it under the terms of the GNU General Public License as published by
00009  * the Free Software Foundation; either version 3, or (at your option)
00010  * any later version.
00011  * 
00012  * GNU Radio is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00015  * GNU General Public License for more details.
00016  * 
00017  * You should have received a copy of the GNU General Public License
00018  * along with GNU Radio; see the file COPYING.  If not, write to
00019  * the Free Software Foundation, Inc., 51 Franklin Street,
00020  * Boston, MA 02110-1301, USA.
00021  */
00022 
00023 #ifndef _GRI_AGC2_CC_H_
00024 #define _GRI_AGC2_CC_H_
00025 
00026 #include <gr_core_api.h>
00027 #include <math.h>
00028 
00029 /*!
00030  * \brief high performance Automatic Gain Control class
00031  *
00032  * For Power the absolute value of the complex number is used.
00033  */
00034 class GR_CORE_API gri_agc2_cc {
00035 
00036  public:
00037   gri_agc2_cc (float attack_rate = 1e-1, float decay_rate = 1e-2, float reference = 1.0, 
00038                float gain = 1.0, float max_gain = 0.0)
00039     : _attack_rate(attack_rate), _decay_rate(decay_rate), _reference(reference),
00040       _gain(gain), _max_gain(max_gain) {};
00041 
00042   float decay_rate () const  { return _decay_rate; }
00043   float attack_rate () const { return _attack_rate; }
00044   float reference () const   { return _reference; }
00045   float gain () const        { return _gain;  }
00046   float max_gain() const     { return _max_gain; }
00047 
00048   void set_decay_rate (float rate) { _decay_rate = rate; }
00049   void set_attack_rate (float rate) { _attack_rate = rate; }
00050   void set_reference (float reference) { _reference = reference; }
00051   void set_gain (float gain) { _gain = gain; }
00052   void set_max_gain(float max_gain) { _max_gain = max_gain; }
00053 
00054   gr_complex scale (gr_complex input){
00055     gr_complex output = input * _gain;
00056     
00057     float tmp = -_reference + sqrt(output.real()*output.real() + 
00058                                    output.imag()*output.imag());
00059     float rate = _decay_rate;
00060     if((tmp) > _gain)
00061         rate = _attack_rate;
00062     _gain -= tmp*rate;
00063     
00064 #if 0
00065     fprintf(stdout, "rate = %f\ttmp = %f\t gain = %f\n", rate, tmp, _gain);
00066 #endif
00067 
00068     // Not sure about this; will blow up if _gain < 0 (happens when rates are too high),
00069     // but is this the solution?
00070     if (_gain < 0.0)
00071         _gain = 10e-5;
00072 
00073     if (_max_gain > 0.0 && _gain > _max_gain)
00074        _gain = _max_gain;                                                    
00075     return output;
00076   }
00077 
00078   void scaleN (gr_complex output[], const gr_complex input[], unsigned n){
00079     for (unsigned i = 0; i < n; i++)
00080       output[i] = scale (input[i]);
00081   }
00082   
00083  protected:
00084   float _attack_rate;           // attack rate for fast changing signals
00085   float _decay_rate;            // decay rate for slow changing signals
00086   float _reference;             // reference value
00087   float _gain;                  // current gain
00088   float _max_gain;              // max allowable gain
00089 };
00090 
00091 #endif /* _GRI_AGC2_CC_H_ */