/*! * \file notch_cc.cc * \brief Implements a multi state notch filter algorithm * \author Antonio Ramos (antonio.ramosdet(at)gmail.com) * * ----------------------------------------------------------------------------- * * GNSS-SDR is a Global Navigation Satellite System software-defined receiver. * This file is part of GNSS-SDR. * * Copyright (C) 2010-2019 (see AUTHORS file for a list of contributors) * SPDX-License-Identifier: GPL-3.0-or-later * * ----------------------------------------------------------------------------- */ #include "notch_cc.h" #include #include #include #include #include #include notch_sptr make_notch_filter(float pfa, float p_c_factor, int32_t length, int32_t n_segments_est, int32_t n_segments_reset) { return notch_sptr(new Notch(pfa, p_c_factor, length, n_segments_est, n_segments_reset)); } Notch::Notch(float pfa, float p_c_factor, int32_t length, int32_t n_segments_est, int32_t n_segments_reset) : gr::block("Notch", gr::io_signature::make(1, 1, sizeof(gr_complex)), gr::io_signature::make(1, 1, sizeof(gr_complex))) { const int32_t alignment_multiple = volk_get_alignment() / sizeof(gr_complex); set_alignment(std::max(1, alignment_multiple)); pfa_ = pfa; noise_pow_est_ = 0.0; p_c_factor_ = gr_complex(p_c_factor, 0.0); length_ = length; // Set the number of samples per segment filter_state_ = false; // Initial state of the filter n_deg_fred_ = 2 * length_; // Number of dregrees of freedom n_segments_ = 0; n_segments_est_ = n_segments_est; // Set the number of segments for noise power estimation n_segments_reset_ = n_segments_reset; // Set the period (in segments) when the noise power is estimated z_0_ = gr_complex(0.0, 0.0); boost::math::chi_squared_distribution my_dist_(n_deg_fred_); thres_ = boost::math::quantile(boost::math::complement(my_dist_, pfa_)); c_samples_ = volk_gnsssdr::vector(length_); angle_ = volk_gnsssdr::vector(length_); power_spect_ = volk_gnsssdr::vector(length_); last_out_ = gr_complex(0.0, 0.0); d_fft_ = gnss_fft_fwd_make_unique(length_); } int Notch::general_work(int noutput_items, gr_vector_int &ninput_items __attribute__((unused)), gr_vector_const_void_star &input_items, gr_vector_void_star &output_items) { int32_t index_out = 0; float sig2dB = 0.0; float sig2lin = 0.0; lv_32fc_t dot_prod_; const auto *in = reinterpret_cast(input_items[0]); auto *out = reinterpret_cast(output_items[0]); in++; while ((index_out + length_) < noutput_items) { if ((n_segments_ < n_segments_est_) && (filter_state_ == false)) { memcpy(d_fft_->get_inbuf(), in, sizeof(gr_complex) * length_); d_fft_->execute(); volk_32fc_s32f_power_spectrum_32f(power_spect_.data(), d_fft_->get_outbuf(), 1.0, length_); volk_32f_s32f_calc_spectral_noise_floor_32f(&sig2dB, power_spect_.data(), 15.0, length_); sig2lin = std::pow(10.0F, (sig2dB / 10.0F)) / (static_cast(n_deg_fred_)); noise_pow_est_ = (static_cast(n_segments_) * noise_pow_est_ + sig2lin) / (static_cast(n_segments_ + 1)); memcpy(out, in, sizeof(gr_complex) * length_); } else { volk_32fc_x2_conjugate_dot_prod_32fc(&dot_prod_, in, in, length_); if ((lv_creal(dot_prod_) / noise_pow_est_) > thres_) { if (filter_state_ == false) { filter_state_ = true; last_out_ = gr_complex(0.0, 0.0); } volk_32fc_x2_multiply_conjugate_32fc(c_samples_.data(), in, (in - 1), length_); volk_32fc_s32f_atan2_32f(angle_.data(), c_samples_.data(), static_cast(1.0), length_); for (int32_t aux = 0; aux < length_; aux++) { z_0_ = std::exp(gr_complex(0.0, 1.0) * (*(angle_.data() + aux))); *(out + aux) = *(in + aux) - z_0_ * (*(in + aux - 1)) + p_c_factor_ * z_0_ * last_out_; last_out_ = *(out + aux); } } else { if (n_segments_ > n_segments_reset_) { n_segments_ = 0; } filter_state_ = false; memcpy(out, in, sizeof(gr_complex) * length_); } } index_out += length_; n_segments_++; in += length_; out += length_; } consume_each(index_out); return index_out; }