gri_control_loop.h

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/* -*- c++ -*- */
/*
 * Copyright 2011 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 GRI_CONTROL_LOOP
#define GRI_CONTROL_LOOP

#include <gr_core_api.h>

class GR_CORE_API gri_control_loop
{
 protected:
  float d_phase, d_freq;
  float d_max_freq, d_min_freq;
  float d_damping, d_loop_bw;
  float d_alpha, d_beta;

 public:
  gri_control_loop(float loop_bw, float max_freq, float min_freq);
  virtual ~gri_control_loop();

  /*! \brief update the system gains from the loop bandwidth and damping factor
   *
   *  This function updates the system gains based on the loop
   *  bandwidth and damping factor of the system.
   *  These two factors can be set separately through their own
   *  set functions.
   */
  void update_gains();

  /*! \brief update the system gains from the loop bandwidth and damping factor
   *
   *  This function updates the system gains based on the loop
   *  bandwidth and damping factor of the system.
   *  These two factors can be set separately through their own
   *  set functions.
   */
  void advance_loop(float error);

  /*! \brief Keep the phase between -2pi and 2pi
   *
   * This function keeps the phase between -2pi and 2pi. If the phase
   * is greater than 2pi by d, it wraps around to be -2pi+d; similarly if
   * it is less than -2pi by d, it wraps around to 2pi-d.
   *
   * This function should be called after advance_loop to keep the phase
   * in a good operating region. It is set as a separate method in case
   * another way is desired as this is fairly heavy-handed.
   */
  void phase_wrap();

  /*! \brief Keep the frequency between d_min_freq and d_max_freq
   *
   * This function keeps the frequency between d_min_freq and d_max_freq.
   * If the frequency is greater than d_max_freq, it is set to d_max_freq.
   * If the frequency is less than d_min_freq, it is set to d_min_freq.
   *
   * This function should be called after advance_loop to keep the frequency
   * in the specified region. It is set as a separate method in case
   * another way is desired as this is fairly heavy-handed.
   */
  void frequency_limit();

  /*******************************************************************
    SET FUNCTIONS
  *******************************************************************/

  /*!
   * \brief Set the loop bandwidth
   *
   * Set the loop filter's bandwidth to \p bw. This should be between 
   * 2*pi/200 and 2*pi/100  (in rads/samp). It must also be a positive
   * number.
   *
   * When a new damping factor is set, the gains, alpha and beta, of the loop
   * are recalculated by a call to update_gains().
   *
   * \param bw    (float) new bandwidth
   *
   */
  void set_loop_bandwidth(float bw);

  /*!
   * \brief Set the loop damping factor
   *
   * Set the loop filter's damping factor to \p df. The damping factor
   * should be sqrt(2)/2.0 for critically damped systems.
   * Set it to anything else only if you know what you are doing. It must
   * be a number between 0 and 1.
   *
   * When a new damping factor is set, the gains, alpha and beta, of the loop
   * are recalculated by a call to update_gains().
   *
   * \param df    (float) new damping factor
   *
   */
  void set_damping_factor(float df);

  /*!
   * \brief Set the loop gain alpha
   *
   * Set's the loop filter's alpha gain parameter.
   *
   * This value should really only be set by adjusting the loop bandwidth
   * and damping factor.
   *
   * \param alpha    (float) new alpha gain
   *
   */
  void set_alpha(float alpha);

  /*!
   * \brief Set the loop gain beta
   *
   * Set's the loop filter's beta gain parameter.
   *
   * This value should really only be set by adjusting the loop bandwidth
   * and damping factor.
   *
   * \param beta    (float) new beta gain
   *
   */
  void set_beta(float beta);

  /*!
   * \brief Set the Costas loop's frequency.
   *
   * Set's the Costas Loop's frequency. While this is normally updated by the
   * inner loop of the algorithm, it could be useful to manually initialize,
   * set, or reset this under certain circumstances.
   *
   * \param freq    (float) new frequency
   *
   */
  void set_frequency(float freq);

  /*!
   * \brief Set the Costas loop's phase.
   *
   * Set's the Costas Loop's phase. While this is normally updated by the
   * inner loop of the algorithm, it could be useful to manually initialize,
   * set, or reset this under certain circumstances.
   *
   * \param phase    (float) new phase
   *
   */
  void set_phase(float phase);

   
  /*******************************************************************
    GET FUNCTIONS
  *******************************************************************/

  /*!
   * \brief Returns the loop bandwidth
   */
  float get_loop_bandwidth() const;

  /*!
   * \brief Returns the loop damping factor
   */
  float get_damping_factor() const;

  /*!
   * \brief Returns the loop gain alpha
   */
  float get_alpha() const;

  /*!
   * \brief Returns the loop gain beta
   */
  float get_beta() const;

  /*!
   * \brief Get the Costas loop's frequency estimate
   */
  float get_frequency() const;

  /*!
   * \brief Get the Costas loop's phase estimate
   */
  float get_phase() const;
};

#endif /* GRI_CONTROL_LOOP */