mirror of https://github.com/gnss-sdr/gnss-sdr
123 lines
4.3 KiB
C++
123 lines
4.3 KiB
C++
/*!
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* \file tracking_discriminators.cc
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* \brief Implementation of a library with a set of code tracking
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* and carrier tracking discriminators that is used by the tracking algorithms.
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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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* -------------------------------------------------------------------------
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*
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* Copyright (C) 2010-2012 (see AUTHORS file for a list of contributors)
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*
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* GNSS-SDR is a software defined Global Navigation
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* Satellite Systems receiver
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*
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* This file is part of GNSS-SDR.
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*
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* GNSS-SDR is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* at your option) any later version.
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*
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* GNSS-SDR is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GNSS-SDR. If not, see <http://www.gnu.org/licenses/>.
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*
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* -------------------------------------------------------------------------
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*/
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#include "tracking_discriminators.h"
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#include <math.h>
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// All the outputs are in RADIANS
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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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float fll_four_quadrant_atan(gr_complex prompt_s1, gr_complex prompt_s2,float t1, float t2)
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{
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float cross,dot;
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dot = prompt_s1.imag()*prompt_s2.imag() + prompt_s1.real()*prompt_s2.real();
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cross = prompt_s1.imag()*prompt_s2.real() - prompt_s2.imag()*prompt_s1.real();
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return atan2(cross, dot) / (t2-t1);
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}
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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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float pll_four_quadrant_atan(gr_complex prompt_s1)
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{
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return atan2(prompt_s1.real(), prompt_s1.imag());
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}
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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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float pll_cloop_two_quadrant_atan(gr_complex prompt_s1)
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{
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if (prompt_s1.imag() != 0.0)
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{
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return atan(prompt_s1.real() / prompt_s1.imag());
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}
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else
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{
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return 0;
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}
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}
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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{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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float dll_nc_e_minus_l_normalized(gr_complex early_s1, gr_complex late_s1)
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{
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float P_early, P_late;
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P_early = std::abs(early_s1);
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P_late = std::abs(late_s1);
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return (P_early - P_late) / ((P_early + P_late));
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}
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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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float 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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{
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float P_early, P_late;
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P_early = std::sqrt(std::norm(very_early_s1)+std::norm(early_s1));
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P_late = std::sqrt(std::norm(very_late_s1)+std::norm(late_s1));
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return (P_early - P_late) / ((P_early + P_late));
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}
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