mirror of https://github.com/gnss-sdr/gnss-sdr
78 lines
2.4 KiB
C++
78 lines
2.4 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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* 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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#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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const float Wn = lbw * 8.0F * zeta / (4.0F * zeta * zeta + 1.0F);
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// solve for t1 & t2
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*tau1 = k / (Wn * Wn);
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*tau2 = 2.0F * 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()
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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 = d_old_code_nco + (d_tau2_code / d_tau1_code) * (DLL_discriminator - d_old_code_error) + (DLL_discriminator + d_old_code_error) * (d_pdi_code / (2.0F * 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(float pdi_code) : d_pdi_code(pdi_code),
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d_dlldampingratio(0.7)
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{
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}
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Tracking_2nd_DLL_filter::Tracking_2nd_DLL_filter() : d_pdi_code(0.001),
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d_dlldampingratio(0.7)
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{
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}
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void Tracking_2nd_DLL_filter::set_pdi(float pdi_code)
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{
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d_pdi_code = pdi_code; // Summation interval for code
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}
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