222 lines
6.8 KiB
C++
222 lines
6.8 KiB
C++
/* -*- c++ -*- */
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/*
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* gr-satnogs: SatNOGS GNU Radio Out-Of-Tree Module
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*
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* Copyright (C) 2016, Libre Space Foundation <http://librespacefoundation.org/>
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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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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include <gnuradio/io_signature.h>
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#include "doppler_correction_cc_impl.h"
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#include <satnogs/log.h>
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#include <volk/volk.h>
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namespace gr {
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namespace satnogs {
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doppler_correction_cc::sptr
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doppler_correction_cc::make(double target_freq,
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double offset,
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double sampling_rate,
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size_t corrections_per_sec)
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{
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return gnuradio::get_initial_sptr(
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new doppler_correction_cc_impl(target_freq, offset,
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sampling_rate,
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corrections_per_sec));
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}
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/*
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* The private constructor
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*/
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doppler_correction_cc_impl::doppler_correction_cc_impl(
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double target_freq,
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double offset,
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double sampling_rate,
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size_t corrections_per_sec) :
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gr::sync_block("doppler_correction_cc",
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gr::io_signature::make(1, 1, sizeof(gr_complex)),
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gr::io_signature::make(1, 1, sizeof(gr_complex))),
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d_target_freq(target_freq),
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d_offset(offset),
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d_samp_rate(sampling_rate),
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d_update_period(sampling_rate / corrections_per_sec),
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d_est_thrhld(7),
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d_corrections_per_sec(corrections_per_sec),
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d_nco(),
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/* A 3-rd order polynomial curve fitting is more than enough */
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d_doppler_fit_engine(3),
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d_freq_diff(offset),
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d_have_est(false),
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d_freq_est_num(0),
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d_corrections(0),
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d_corrected_samples(0)
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{
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message_port_register_in(pmt::mp("freq"));
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message_port_register_in(pmt::mp("reset"));
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/*
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* NOTE:
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* Set the maximum number of samples to be equivalent of half a second.
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* With this way we are sure that at least one frequency message
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* per second will be processed.
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*
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* This is taken into consideration due to the fact that the work()
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* and the input message handler are NOT reentrant.
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*/
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set_max_noutput_items(d_samp_rate / 2.0);
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set_alignment(8);
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set_msg_handler(
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pmt::mp("freq"),
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boost::bind(&doppler_correction_cc_impl::new_freq, this, _1));
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set_msg_handler(
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pmt::mp("reset"),
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boost::bind(&doppler_correction_cc_impl::reset, this, _1));
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d_nco.set_freq((2 * M_PI * (-d_freq_diff)) / d_samp_rate);
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/* Allocate the buffer that will hold the predicted frequency differences */
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d_predicted_freqs = new double[d_corrections_per_sec];
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/* Allocate aligned memory for the NCO */
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d_nco_buff = (gr_complex *) volk_malloc(
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d_update_period * sizeof(gr_complex), 32);
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if (!d_nco_buff) {
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throw std::runtime_error("Could not allocate NCO memory");
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}
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}
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void
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doppler_correction_cc_impl::new_freq(pmt::pmt_t msg)
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{
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boost::mutex::scoped_lock lock(d_mutex);
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double new_freq;
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new_freq = pmt::to_double(msg);
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d_freq_diff = new_freq - (d_target_freq - d_offset);
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if (!d_have_est) {
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d_freq_est_num++;
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d_doppler_freqs.push_back(
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freq_drift(nitems_written(0), d_freq_diff));
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if (d_freq_est_num > d_est_thrhld - 1) {
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d_doppler_fit_engine.fit(d_doppler_freqs);
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d_doppler_fit_engine.predict_freqs(d_predicted_freqs,
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d_corrections_per_sec,
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d_update_period);
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d_have_est = true;
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}
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}
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else {
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d_doppler_freqs.pop_front();
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d_doppler_freqs.push_back(
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freq_drift(nitems_written(0), d_freq_diff));
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/* Fit the doppler drift based on the new estimated frequency */
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d_doppler_fit_engine.fit(d_doppler_freqs);
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/* Predict the frequency differences for the near future */
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d_doppler_fit_engine.predict_freqs(d_predicted_freqs,
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d_corrections_per_sec,
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d_update_period);
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d_corrections = 0;
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}
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}
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void
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doppler_correction_cc_impl::reset(pmt::pmt_t msg)
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{
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boost::mutex::scoped_lock lock(d_mutex);
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d_doppler_freqs.clear();
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d_freq_est_num = 0;
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d_corrections = 0;
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d_have_est = false;
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}
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/*
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* Our virtual destructor.
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*/
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doppler_correction_cc_impl::~doppler_correction_cc_impl()
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{
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delete[] d_predicted_freqs;
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volk_free(d_nco_buff);
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}
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int
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doppler_correction_cc_impl::work(int noutput_items,
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gr_vector_const_void_star &input_items,
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gr_vector_void_star &output_items)
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{
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const gr_complex *in = (const gr_complex *) input_items[0];
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gr_complex *out = (gr_complex *) output_items[0];
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int produced = 0;
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size_t cnt;
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/*
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* If we do not have an estimation yet, just copy the input to the output.
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* Otherwise perform Doppler correction, using the fitted curve indicating
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* the frequency drift.
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*/
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if (d_have_est) {
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while (produced < noutput_items) {
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/*
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* If no samples have been corrected from the current correction step
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* compute and store the NCO buffer with the corresponding frequency
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*/
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if (d_corrected_samples == 0) {
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d_nco.set_freq(
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2 * M_PI * (-d_predicted_freqs[d_corrections]) / d_samp_rate);
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d_nco.sincos(d_nco_buff, d_update_period, 1.0);
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d_corrections++;
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/*
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* The doppler estimation may fail/delay. In such a case the block
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* should continue using the predicted frequencies
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*/
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if (d_corrections == d_corrections_per_sec) {
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d_doppler_fit_engine.predict_freqs(d_predicted_freqs,
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d_corrections_per_sec,
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d_update_period);
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d_corrections = 0;
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}
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}
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cnt = std::min(d_update_period - d_corrected_samples,
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(size_t)(noutput_items - produced));
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/* Perform the doppler shift correction */
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volk_32fc_x2_multiply_32fc(out + produced, in + produced,
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d_nco_buff + d_corrected_samples, cnt);
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/* Make the proper advances */
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produced += (int) cnt;
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d_corrected_samples += cnt;
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if (d_corrected_samples == d_update_period) {
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d_corrected_samples = 0;
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}
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}
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}
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else {
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memcpy(out, in, noutput_items * sizeof(gr_complex));
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}
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return noutput_items;
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}
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} /* namespace satnogs */
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} /* namespace gr */
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