mirror of https://github.com/gnss-sdr/gnss-sdr
92 lines
2.7 KiB
C++
92 lines
2.7 KiB
C++
/*!
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* \file tracking_2nd_DLL_filter.cc
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* \brief Implementation of a 2nd order DLL filter for code tracking loop.
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* \author Javier Arribas, 2011. jarribas(at)cttc.es
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*
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* Class that implements 2 order PLL filter for code tracking loop.
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* The algorithm is described in :
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* K.Borre, D.M.Akos, N.Bertelsen, P.Rinder, and S.~H.~Jensen, A Software-Defined
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* GPS and Galileo Receiver. A Single-Frequency Approach,
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* Birkhauser, 2007, Applied and Numerical Harmonic Analysis.
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*
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* -------------------------------------------------------------------------
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*
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* Copyright (C) 2010-2011 (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_2nd_DLL_filter.h"
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void Tracking_2nd_DLL_filter::calculate_lopp_coef(float* tau1,float* tau2, float lbw, float zeta, float k)
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{
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// Solve natural frequency
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float Wn;
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Wn = lbw*8*zeta / (4*zeta*zeta + 1);
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// solve for t1 & t2
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*tau1 = k / (Wn * Wn);
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*tau2 = (2.0 * zeta) / Wn;
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}
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void Tracking_2nd_DLL_filter::set_DLL_BW(float dll_bw_hz)
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{
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//Calculate filter coefficient values
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d_dllnoisebandwidth = dll_bw_hz;
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calculate_lopp_coef(&d_tau1_code, &d_tau2_code, d_dllnoisebandwidth, d_dlldampingratio, 1.0);// Calculate filter coefficient values
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}
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void Tracking_2nd_DLL_filter::initialize(float d_acq_code_phase_samples)
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{
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// code tracking loop parameters
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d_old_code_nco = 0.0;
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d_old_code_error = 0.0;
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}
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float Tracking_2nd_DLL_filter::get_code_nco(float DLL_discriminator)
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{
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float code_nco;
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code_nco = d_old_code_nco + (d_tau2_code/d_tau1_code)*(DLL_discriminator - d_old_code_error) + DLL_discriminator * (d_pdi_code/d_tau1_code);
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d_old_code_nco = code_nco;
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d_old_code_error = DLL_discriminator; //[chips]
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return code_nco;
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}
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Tracking_2nd_DLL_filter::Tracking_2nd_DLL_filter ()
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{
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d_pdi_code = 0.001;// Summation interval for code
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d_dlldampingratio = 0.7;
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}
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Tracking_2nd_DLL_filter::~Tracking_2nd_DLL_filter ()
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{}
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