mirror of https://github.com/gnss-sdr/gnss-sdr
202 lines
6.2 KiB
C++
202 lines
6.2 KiB
C++
/*!
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* \file tracking_discriminators.h
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* \brief Interface of a library with a set of code tracking and carrier
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* tracking discriminators.
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* \authors <ul>
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* <li> Javier Arribas, 2011. jarribas(at)cttc.es
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* <li> Luis Esteve, 2012. luis(at)epsilon-formacion.com
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* </ul>
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*
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* Library with a set of code tracking and carrier tracking discriminators
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* that is used by the tracking algorithms.
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*
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* -----------------------------------------------------------------------------
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*
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* GNSS-SDR is a Global Navigation Satellite System software-defined receiver.
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* This file is part of GNSS-SDR.
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*
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* Copyright (C) 2010-2020 (see AUTHORS file for a list of contributors)
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* SPDX-License-Identifier: GPL-3.0-or-later
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*
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* -----------------------------------------------------------------------------
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*/
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#ifndef GNSS_SDR_TRACKING_DISCRIMINATORS_H
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#define GNSS_SDR_TRACKING_DISCRIMINATORS_H
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#include <gnuradio/gr_complex.h>
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#include <cmath>
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/** \addtogroup Tracking
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* \{ */
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/** \addtogroup Tracking_libs
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* \{ */
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/*! brief FLL four quadrant arctan discriminator
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*
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* FLL four quadrant arctan discriminator:
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* \f{equation}
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* \frac{\phi_2-\phi_1}{t_2-t1}=\frac{ATAN2(cross,dot)}{t_1-t_2},
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* \f}
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* where \f$cross=I_{PS1}Q_{PS2}-I_{PS2}Q_{PS1}\f$ and \f$dot=I_{PS1}I_{PS2}+Q_{PS1}Q_{PS2}\f$,
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* \f$I_{PS1},Q_{PS1}\f$ are the inphase and quadrature prompt correlator outputs respectively at sample time \f$t_1\f$, and
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* \f$I_{PS2},Q_{PS2}\f$ are the inphase and quadrature prompt correlator outputs respectively at sample time \f$t_2\f$. The output is in [radians/second].
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*/
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double fll_four_quadrant_atan(gr_complex prompt_s1, gr_complex prompt_s2, double t1, double t2);
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/*
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* FLL differential arctan discriminator:
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* \f{equation}
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* 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)}))
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* \f}
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* The output is in [radians/second].
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*/
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double fll_diff_atan(gr_complex prompt_s1, gr_complex prompt_s2, double t1, double t2);
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/*! \brief Phase unwrapping function, input is [rad]
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*/
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double phase_unwrap(double phase_rad);
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/*! \brief PLL four quadrant arctan discriminator
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*
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* PLL four quadrant arctan discriminator:
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* \f{equation}
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* \phi=ATAN2(Q_{PS},I_{PS}),
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* \f}
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* where \f$I_{PS1},Q_{PS1}\f$ are the inphase and quadrature prompt correlator outputs respectively. The output is in [radians].
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*/
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double pll_four_quadrant_atan(gr_complex prompt_s1);
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/*! \brief PLL Costas loop two quadrant arctan discriminator
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*
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* PLL Costas loop two quadrant arctan discriminator:
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* \f{equation}
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* \phi=ATAN\left(\frac{Q_{PS}}{I_{PS}}\right),
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* \f}
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* where \f$I_{PS1},Q_{PS1}\f$ are the inphase and quadrature prompt correlator outputs respectively. The output is in [radians].
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*/
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double pll_cloop_two_quadrant_atan(gr_complex prompt_s1);
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/*! \brief DLL Noncoherent Early minus Late envelope normalized discriminator
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*
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* DLL Noncoherent Early minus Late envelope normalized discriminator:
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* \f{equation}
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* error = \frac{y_{intercept} - \text{slope} * \epsilon}{\text{slope}} \frac{E-L}{E+L},
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* \f}
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* where \f$E=\sqrt{I_{ES}^2+Q_{ES}^2}\f$ is the Early correlator output absolute value and
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* \f$L=\sqrt{I_{LS}^2+Q_{LS}^2}\f$ is the Late correlator output absolute value. The output is in [chips].
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*/
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double dll_nc_e_minus_l_normalized(gr_complex early_s1, gr_complex late_s1, float spc = 0.5, float slope = 1.0, float y_intercept = 1.0);
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/*! \brief DLL Noncoherent Very Early Minus Late Power (VEMLP) normalized discriminator
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*
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* DLL Noncoherent Very Early Minus Late Power (VEMLP) normalized discriminator, using the outputs
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* of four correlators, Very Early (VE), Early (E), Late (L) and Very Late (VL):
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* \f{equation}
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* error=\frac{E-L}{E+L},
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* \f}
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* where \f$E=\sqrt{I_{VE}^2+Q_{VE}^2+I_{E}^2+Q_{E}^2}\f$ and
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* \f$L=\sqrt{I_{VL}^2+Q_{VL}^2+I_{L}^2+Q_{L}^2}\f$ . The output is in [chips].
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*/
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double dll_nc_vemlp_normalized(gr_complex very_early_s1, gr_complex early_s1, gr_complex late_s1, gr_complex very_late_s1);
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template <typename Fun>
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double CalculateSlope(Fun &&f, double x)
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{
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static constexpr double dx = 1e-6;
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return (f(x + dx / 2.0) - f(x - dx / 2.0)) / dx;
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}
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template <typename Fun>
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double CalculateSlopeAbs(Fun &&f, double x)
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{
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static constexpr double dx = 1e-6;
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return (std::abs(f(x + dx / 2.0)) - std::abs(f(x - dx / 2.0))) / dx;
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}
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template <typename Fun>
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double GetYIntercept(Fun &&f, double x)
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{
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double slope = CalculateSlope(f, x);
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double y1 = f(x);
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return y1 - slope * x;
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}
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template <typename Fun>
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double GetYInterceptAbs(Fun &&f, double x)
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{
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double slope = CalculateSlopeAbs(f, x);
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double y1 = std::abs(f(x));
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return y1 - slope * x;
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}
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// SinBocCorrelationFunction and CosBocCorrelationFunction from
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// Sousa, F. and Nunes, F., "New Expressions for the Autocorrelation
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// Function of BOC GNSS Signals", NAVIGATION - Journal of the Institute
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// of Navigation, March 2013.
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//
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template <int M = 1, int N = M>
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double SinBocCorrelationFunction(double offset_in_chips)
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{
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static constexpr int TWO_P = 2 * M / N;
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double abs_tau = std::abs(offset_in_chips);
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if (abs_tau > 1.0)
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{
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return 0.0;
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}
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int k = static_cast<int>(std::ceil(TWO_P * abs_tau));
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double sgn = ((k & 0x01) == 0 ? 1.0 : -1.0); // (-1)^k
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return sgn * (2.0 * (k * k - k * TWO_P - k) / TWO_P + 1.0 +
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(2 * TWO_P - 2 * k + 1) * abs_tau);
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}
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template <int M = 1, int N = M>
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double CosBocCorrelationFunction(double offset_in_chips)
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{
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static constexpr int TWO_P = 2 * M / N;
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double abs_tau = std::abs(offset_in_chips);
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if (abs_tau > 1.0)
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{
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return 0.0;
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}
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int k = static_cast<int>(std::floor(2.0 * TWO_P * abs_tau));
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if ((k & 0x01) == 0) // k is even
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{
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double sgn = ((k >> 1) & 0x01 ? -1.0 : 1.0); // (-1)^(k/2)
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return sgn * ((2 * k * TWO_P + 2 * TWO_P - k * k) / (2.0 * TWO_P) + (-2 * TWO_P + k - 1) * abs_tau);
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}
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else
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{
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double sgn = (((k + 1) >> 1) & 0x01 ? -1.0 : 1.0); // (-1)^((k+1)/2)
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return sgn * ((k * k + 2 * k - 2 * k * TWO_P + 1) / (2.0 * TWO_P) + (2 * TWO_P - k - 2) * abs_tau);
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}
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}
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/** \} */
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/** \} */
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#endif // GNSS_SDR_TRACKING_DISCRIMINATORS_H
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