mirror of
https://github.com/fairwaves/UHD-Fairwaves.git
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86 lines
3.3 KiB
C++
86 lines
3.3 KiB
C++
//
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// Copyright 2010 Ettus Research LLC
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//
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// This program 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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// This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
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//
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#include <vector>
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#include <complex>
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#include <cmath>
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#include <fstream>
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struct result_t{double freq, real_corr, imag_corr, sup;};
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/***********************************************************************
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* Constants
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**********************************************************************/
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static const double tau = 6.28318531;
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static const double alpha = 0.0001; //very tight iir filter
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static const size_t wave_table_len = 8192;
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static const size_t num_search_steps = 5;
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static const size_t num_search_iters = 7;
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static const size_t skip_initial_samps = 20;
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/***********************************************************************
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* Sinusoid wave table
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**********************************************************************/
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static inline std::vector<std::complex<float> > gen_table(void){
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std::vector<std::complex<float> > wave_table(wave_table_len);
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for (size_t i = 0; i < wave_table_len; i++){
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wave_table[i] = std::polar<float>(1.0, (tau*i)/wave_table_len);
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}
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return wave_table;
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}
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static inline std::complex<float> wave_table_lookup(const size_t index){
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static const std::vector<std::complex<float> > wave_table = gen_table();
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return wave_table[index % wave_table_len];
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}
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/***********************************************************************
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* Compute power of a tone
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**********************************************************************/
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static inline double compute_tone_dbrms(
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const std::vector<std::complex<float> > &samples,
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const double freq //freq is fractional
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){
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//shift the samples so the tone at freq is down at DC
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std::vector<std::complex<double> > shifted(samples.size() - skip_initial_samps);
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for (size_t i = 0; i < shifted.size(); i++){
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shifted[i] = std::complex<double>(samples[i+skip_initial_samps]) * std::polar<double>(1.0, -freq*tau*i);
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}
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//filter the samples with a narrow low pass
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std::complex<double> iir_output = 0, iir_last = 0;
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double output = 0;
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for (size_t i = 0; i < shifted.size(); i++){
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iir_output = alpha * shifted[i] + (1-alpha)*iir_last;
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iir_last = iir_output;
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output += std::abs(iir_output);
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}
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return 20*std::log10(output/shifted.size());
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}
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/***********************************************************************
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* Write a dat file
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**********************************************************************/
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static inline void write_samples_to_file(
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const std::vector<std::complex<float> > &samples, const std::string &file
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){
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std::ofstream outfile(file.c_str(), std::ofstream::binary);
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outfile.write((const char*)&samples.front(), samples.size()*sizeof(std::complex<float>));
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outfile.close();
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}
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