mirror of https://github.com/gnss-sdr/gnss-sdr
122 lines
5.3 KiB
C++
122 lines
5.3 KiB
C++
/*!
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* \file notch_cc.cc
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* \brief Implements a multi state notch filter algorithm
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* \author Antonio Ramos (antonio.ramosdet(at)gmail.com)
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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) 2010-2019 (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 "notch_cc.h"
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#include <boost/math/distributions/chi_squared.hpp>
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#include <gnuradio/io_signature.h>
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#include <volk/volk.h>
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#include <algorithm>
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#include <cmath>
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#include <cstring>
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notch_sptr make_notch_filter(float pfa, float p_c_factor,
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int32_t length, int32_t n_segments_est, int32_t n_segments_reset)
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{
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return notch_sptr(new Notch(pfa, p_c_factor, length, n_segments_est, n_segments_reset));
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}
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Notch::Notch(float pfa,
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float p_c_factor,
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int32_t length,
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int32_t n_segments_est,
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int32_t n_segments_reset) : gr::block("Notch",
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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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{
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const int32_t alignment_multiple = volk_get_alignment() / sizeof(gr_complex);
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set_alignment(std::max(1, alignment_multiple));
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pfa_ = pfa;
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noise_pow_est_ = 0.0;
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p_c_factor_ = gr_complex(p_c_factor, 0.0);
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length_ = length; // Set the number of samples per segment
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filter_state_ = false; // Initial state of the filter
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n_deg_fred_ = 2 * length_; // Number of dregrees of freedom
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n_segments_ = 0;
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n_segments_est_ = n_segments_est; // Set the number of segments for noise power estimation
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n_segments_reset_ = n_segments_reset; // Set the period (in segments) when the noise power is estimated
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z_0_ = gr_complex(0.0, 0.0);
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boost::math::chi_squared_distribution<float> my_dist_(n_deg_fred_);
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thres_ = boost::math::quantile(boost::math::complement(my_dist_, pfa_));
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c_samples_ = volk_gnsssdr::vector<gr_complex>(length_);
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angle_ = volk_gnsssdr::vector<float>(length_);
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power_spect_ = volk_gnsssdr::vector<float>(length_);
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last_out_ = gr_complex(0.0, 0.0);
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d_fft_ = gnss_fft_fwd_make_unique(length_);
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}
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int Notch::general_work(int noutput_items, gr_vector_int &ninput_items __attribute__((unused)),
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gr_vector_const_void_star &input_items, gr_vector_void_star &output_items)
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{
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int32_t index_out = 0;
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float sig2dB = 0.0;
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float sig2lin = 0.0;
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lv_32fc_t dot_prod_;
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const auto *in = reinterpret_cast<const gr_complex *>(input_items[0]);
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auto *out = reinterpret_cast<gr_complex *>(output_items[0]);
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in++;
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while ((index_out + length_) < noutput_items)
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{
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if ((n_segments_ < n_segments_est_) && (filter_state_ == false))
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{
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memcpy(d_fft_->get_inbuf(), in, sizeof(gr_complex) * length_);
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d_fft_->execute();
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volk_32fc_s32f_power_spectrum_32f(power_spect_.data(), d_fft_->get_outbuf(), 1.0, length_);
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volk_32f_s32f_calc_spectral_noise_floor_32f(&sig2dB, power_spect_.data(), 15.0, length_);
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sig2lin = std::pow(10.0F, (sig2dB / 10.0F)) / (static_cast<float>(n_deg_fred_));
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noise_pow_est_ = (static_cast<float>(n_segments_) * noise_pow_est_ + sig2lin) / (static_cast<float>(n_segments_ + 1));
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memcpy(out, in, sizeof(gr_complex) * length_);
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}
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else
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{
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volk_32fc_x2_conjugate_dot_prod_32fc(&dot_prod_, in, in, length_);
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if ((lv_creal(dot_prod_) / noise_pow_est_) > thres_)
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{
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if (filter_state_ == false)
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{
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filter_state_ = true;
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last_out_ = gr_complex(0.0, 0.0);
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}
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volk_32fc_x2_multiply_conjugate_32fc(c_samples_.data(), in, (in - 1), length_);
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volk_32fc_s32f_atan2_32f(angle_.data(), c_samples_.data(), static_cast<float>(1.0), length_);
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for (int32_t aux = 0; aux < length_; aux++)
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{
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z_0_ = std::exp(gr_complex(0.0, 1.0) * (*(angle_.data() + aux)));
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*(out + aux) = *(in + aux) - z_0_ * (*(in + aux - 1)) + p_c_factor_ * z_0_ * last_out_;
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last_out_ = *(out + aux);
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}
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}
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else
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{
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if (n_segments_ > n_segments_reset_)
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{
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n_segments_ = 0;
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}
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filter_state_ = false;
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memcpy(out, in, sizeof(gr_complex) * length_);
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}
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}
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index_out += length_;
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n_segments_++;
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in += length_;
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out += length_;
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}
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consume_each(index_out);
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return index_out;
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}
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