mirror of
https://github.com/gnss-sdr/gnss-sdr
synced 2024-06-25 22:43:14 +00:00
26b18c19ee
This implements a generic loop filter. Based on the analog PLL filters from Kaplan and Hegarty, with a bilinear (Tustin's) transform from s-plane to z-plane ( 1/s -> T/2 ( 1 + z^-1 )/( 1 - z^-1 ) ) Also added tests. Note the "truth" outputs were derived from an Octave implementation of the loop filter and Octave's builtin filter function
99 lines
3.0 KiB
C++
99 lines
3.0 KiB
C++
/*!
|
|
* \file tracking_loop_filter.h
|
|
* \brief Generic 1st to 3rd order loop filter implementation
|
|
* \author Cillian O'Driscoll, 2015. cillian.odriscoll(at)gmail.com
|
|
*
|
|
* Class implementing a generic 1st, 2nd or 3rd order loop filter. Based
|
|
* on the bilinear transform of the standard Weiner filter.
|
|
*
|
|
* -------------------------------------------------------------------------
|
|
*
|
|
* Copyright (C) 2010-2015 (see AUTHORS file for a list of contributors)
|
|
*
|
|
* GNSS-SDR is a software defined Global Navigation
|
|
* Satellite Systems receiver
|
|
*
|
|
* This file is part of GNSS-SDR.
|
|
*
|
|
* GNSS-SDR 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 of the License, or
|
|
* (at your option) any later version.
|
|
*
|
|
* GNSS-SDR 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 GNSS-SDR. If not, see <http://www.gnu.org/licenses/>.
|
|
*
|
|
* -------------------------------------------------------------------------
|
|
*/
|
|
|
|
#ifndef GNSS_SDR_TRACKING_LOOP_FILTER_H_
|
|
#define GNSS_SDR_TRACKING_LOOP_FILTER_H_
|
|
|
|
#include <vector>
|
|
|
|
|
|
/*!
|
|
* \brief This class implements a generic 1st, 2nd or 3rd order loop filter
|
|
*
|
|
*/
|
|
class Tracking_loop_filter
|
|
{
|
|
private:
|
|
// Store the last inputs and outputs:
|
|
std::vector< float > d_inputs;
|
|
std::vector< float > d_outputs;
|
|
|
|
// Store the filter coefficients:
|
|
std::vector< float > d_input_coefficients;
|
|
std::vector< float > d_output_coefficients;
|
|
|
|
// The loop order:
|
|
int d_loop_order;
|
|
|
|
// The current index in the i/o arrays:
|
|
int d_current_index;
|
|
|
|
// Should the last integrator be included?
|
|
bool d_include_last_integrator;
|
|
|
|
// The noise bandwidth (in Hz)
|
|
// Note this is an approximation only valid when the product of this
|
|
// number and the update interval (T) is small.
|
|
float d_noise_bandwidth;
|
|
|
|
// Loop update interval
|
|
float d_update_interval;
|
|
|
|
// Compute the filter coefficients:
|
|
void update_coefficients(void);
|
|
|
|
|
|
public:
|
|
float get_noise_bandwidth(void) const;
|
|
float get_update_interval(void) const;
|
|
bool get_include_last_integrator(void) const;
|
|
int get_order(void) const;
|
|
|
|
void set_noise_bandwidth( float noise_bandwidth );
|
|
void set_update_interval( float update_interval );
|
|
void set_include_last_integrator( bool include_last_integrator );
|
|
void set_order( int loop_order );
|
|
|
|
void initialize(float initial_output = 0.0);
|
|
float apply(float current_input );
|
|
|
|
Tracking_loop_filter(float update_interval, float noise_bandwidth,
|
|
int loop_order = 2,
|
|
bool include_last_integrator = false );
|
|
|
|
Tracking_loop_filter();
|
|
~Tracking_loop_filter();
|
|
};
|
|
|
|
#endif
|