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Implementation of Differential Arctangent Discriminator for FLL

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This commit is contained in:
Javier Arribas 2019-05-15 17:38:45 +02:00
parent 93bea1591b
commit be5ffe6b67
4 changed files with 51 additions and 3 deletions
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4
src/algorithms/tracking/gnuradio_blocks/dll_pll_veml_tracking.cc
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@ -938,7 +938,9 @@ void dll_pll_veml_tracking::run_dll_pll()
if ((d_pull_in_transitory == true and trk_parameters.enable_fll_pull_in == true) or trk_parameters.enable_fll_steady_state)
{
// FLL discriminator
d_carr_freq_error_hz = fll_four_quadrant_atan(d_P_accu_old, d_P_accu, 0, d_current_correlation_time_s) / GPS_TWO_PI;
//d_carr_freq_error_hz = fll_four_quadrant_atan(d_P_accu_old, d_P_accu, 0, d_current_correlation_time_s) / GPS_TWO_PI;
d_carr_freq_error_hz = fll_diff_atan(d_P_accu_old, d_P_accu, 0, d_current_correlation_time_s) / GPS_TWO_PI;
d_P_accu_old = d_P_accu;
//std::cout << "d_carr_freq_error_hz: " << d_carr_freq_error_hz << std::endl;
// Carrier discriminator filter

32
src/algorithms/tracking/libs/tracking_discriminators.cc
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@ -33,10 +33,26 @@
*/
#include "tracking_discriminators.h"
#include "MATH_CONSTANTS.h"
#include <cmath>
// All the outputs are in RADIANS
double phase_unwrap(double phase_rad)
{
if (phase_rad >= HALF_PI)
{
return phase_rad - PI;
}
else if (phase_rad <= -HALF_PI)
{
return phase_rad + PI;
}
else
{
return phase_rad;
}
}
/*
* FLL four quadrant arctan discriminator:
* \f{equation}
@ -54,6 +70,22 @@ double fll_four_quadrant_atan(gr_complex prompt_s1, gr_complex prompt_s2, double
return atan2(cross, dot) / (t2 - t1);
}
/*
* FLL differential arctan discriminator:
* \f{equation}
* e_{atan}(k)=\frac{1}{t_1-t_2}\text{phase_unwrap}(\tan^-1(\frac{Q(k)}{I(k)})-\tan^-1(\frac{Q(k-1)}{I(k-1)}))
* \f}
* The output is in [radians/second].
*/
double fll_diff_atan(gr_complex prompt_s1, gr_complex prompt_s2, double t1, double t2)
{
double diff_atan = atan(prompt_s2.imag() / prompt_s2.real()) - atan(prompt_s1.imag() / prompt_s1.real());
if (std::isnan(diff_atan))
{
diff_atan = 0;
}
return phase_unwrap(diff_atan) / (t2 - t1);
}
/*
* PLL four quadrant arctan discriminator:

13
src/algorithms/tracking/libs/tracking_discriminators.h
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@ -52,6 +52,19 @@
*/
double fll_four_quadrant_atan(gr_complex prompt_s1, gr_complex prompt_s2, double t1, double t2);
/*
* FLL differential arctan discriminator:
* \f{equation}
* e_{atan}(k)=\frac{1}{t_1-t_2}\text{phase_unwrap}(\tan^-1(\frac{Q(k)}{I(k)})-\tan^-1(\frac{Q(k-1)}{I(k-1)}))
* \f}
* The output is in [radians/second].
*/
double fll_diff_atan(gr_complex prompt_s1, gr_complex prompt_s2, double t1, double t2);
/*! \brief Phase unwrapping function, input is [rad]
*
*/
double phase_unwrap(double phase_rad);
/*! \brief PLL four quadrant arctan discriminator
*

5
src/core/system_parameters/MATH_CONSTANTS.h
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@ -43,8 +43,9 @@
ONE_PI_TWO_PX = (1/Pi)*2^X
*/
const double PI = 3.1415926535897932; //!< pi
const double PI_2 = 2.0 * PI; //!< 2 * pi
const double HALF_PI = 1.570796326794897; //!< pi/2
const double PI = 3.1415926535897932; //!< pi
const double PI_2 = 2.0 * PI; //!< 2 * pi
const double TWO_P3 = (8); //!< 2^3
const double TWO_P4 = (16); //!< 2^4