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https://github.com/gnss-sdr/gnss-sdr
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Add code for C/A signal generation for glonass
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Gastd
@@ -25,6 +25,7 @@ set(GNSS_SPLIBS_SOURCES
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gnss_sdr_sample_counter.cc
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gnss_signal_processing.cc
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gps_sdr_signal_processing.cc
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glonass_l1_signal_processing.cc
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pass_through.cc
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galileo_e5_signal_processing.cc
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complex_byte_to_float_x2.cc
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131
src/algorithms/libs/glonass_l1_signal_processing.cc
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131
src/algorithms/libs/glonass_l1_signal_processing.cc
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/*!
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* \file glonass_l1_signal_processing.cc
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* \brief This class implements various functions for GLONASS L1 CA signals
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* \author Javier Arribas, 2011. jarribas(at)cttc.es
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*
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* Detailed description of the file here if needed.
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*
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* -------------------------------------------------------------------------
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*
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* Copyright (C) 2010-2015 (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 "glonass_l1_signal_processing.h"
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auto auxCeil = [](float x){ return static_cast<int>(static_cast<long>((x)+1)); };
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void glonass_l1_ca_code_gen_complex(std::complex<float>* _dest/*, signed int _prn, unsigned int _chip_shift*/)
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{
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const unsigned int _code_length = 511;
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bool G1[_code_length];
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bool G1_register[9];
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bool feedback1;
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bool aux;
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unsigned int lcv, lcv2;
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for(lcv = 0; lcv < 9; lcv++)
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{
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G1_register[lcv] = 1;
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}
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/* Generate G1 Register */
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for(lcv = 0; lcv < _code_length; lcv++)
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{
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G1[lcv] = G1_register[2];
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feedback1 = G1_register[4]^G1_register[0];
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for(lcv2 = 0; lcv2 < 8; lcv2++)
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{
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G1_register[lcv2] = G1_register[lcv2 + 1];
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}
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G1_register[8] = feedback1;
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}
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/* Generate PRN from G1 Register */
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for(lcv = 0; lcv < _code_length; lcv++)
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{
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aux = G1[lcv];
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if(aux == true)
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{
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_dest[lcv] = std::complex<float>(1, 0);
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}
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else
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{
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_dest[lcv] = std::complex<float>(-1, 0);
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}
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}
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}
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/*
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* Generates complex GLONASS L1 C/A code for the desired SV ID and sampled to specific sampling frequency
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*/
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void glonass_l1_ca_code_gen_complex_sampled(std::complex<float>* _dest, unsigned int _prn, signed int _fs, unsigned int _chip_shift)
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{
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// This function is based on the GNU software GPS for MATLAB in the Kay Borre book
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std::complex<float> _code[511];
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signed int _samplesPerCode, _codeValueIndex;
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float _ts;
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float _tc;
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float aux;
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const signed int _codeFreqBasis = 511000; //Hz
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const signed int _codeLength = 511;
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//--- Find number of samples per spreading code ----------------------------
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_samplesPerCode = static_cast<signed int>(static_cast<double>(_fs) / static_cast<double>(_codeFreqBasis / _codeLength));
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//--- Find time constants --------------------------------------------------
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_ts = 1.0 / static_cast<float>(_fs); // Sampling period in sec
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_tc = 1.0 / static_cast<float>(_codeFreqBasis); // C/A chip period in sec
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glonass_l1_ca_code_gen_complex(_code); //generate C/A code 1 sample per chip
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for (signed int i = 0; i < _samplesPerCode; i++)
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{
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//=== Digitizing =======================================================
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//--- Make index array to read C/A code values -------------------------
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// The length of the index array depends on the sampling frequency -
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// number of samples per millisecond (because one C/A code period is one
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// millisecond).
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// _codeValueIndex = ceil((_ts * ((float)i + 1)) / _tc) - 1;
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aux = (_ts * (i + 1)) / _tc;
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_codeValueIndex = auxCeil( aux ) - 1;
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//--- Make the digitized version of the C/A code -----------------------
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// The "upsampled" code is made by selecting values form the CA code
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// chip array (caCode) for the time instances of each sample.
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if (i == _samplesPerCode - 1)
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{
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//--- Correct the last index (due to number rounding issues) -----------
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_dest[i] = _code[_codeLength - 1];
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}
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else
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{
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_dest[i] = _code[_codeValueIndex]; //repeat the chip -> upsample
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}
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}
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}
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47
src/algorithms/libs/glonass_l1_signal_processing.h
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47
src/algorithms/libs/glonass_l1_signal_processing.h
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@@ -0,0 +1,47 @@
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/*!
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* \file glonass_l1_signal_processing.h
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* \brief This class implements various functions for GLONASS L1 CA signals
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* \author Gabriel Araujo, 2017. gabriel.araujo(at)ieee.org
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*
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* Detailed description of the file here if needed.
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*
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* -------------------------------------------------------------------------
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*
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* Copyright (C) 2010-2017 (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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#ifndef GNSS_SDR_GPS_SDR_SIGNAL_PROCESSING_H_
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#define GNSS_SDR_GPS_SDR_SIGNAL_PROCESSING_H_
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#include <complex>
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//!Generates complex GLONASS L1 C/A code for the desired SV ID and code shift, and sampled to specific sampling frequency
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void glonass_l1_ca_code_gen_complex(std::complex<float>* _dest/*, signed int _prn, unsigned int _chip_shift*/);
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//! Generates N complex GLONASS L1 C/A codes for the desired SV ID and code shift
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void glonass_l1_ca_code_gen_complex_sampled(std::complex<float>* _dest, unsigned int _prn, signed int _fs, unsigned int _chip_shift, unsigned int _ncodes);
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//! Generates complex GLONASS L1 C/A code for the desired SV ID and code shift
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void glonass_l1_ca_code_gen_complex_sampled(std::complex<float>* _dest, unsigned int _prn, signed int _fs, unsigned int _chip_shift);
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#endif /* GNSS_SDR_GPS_SDR_SIGNAL_PROCESSING_H_ */
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