kopia lustrzana https://github.com/Dsplib/libdspl-2.0
182 wiersze
5.5 KiB
C
182 wiersze
5.5 KiB
C
/*
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* Copyright (c) 2015-2024 Sergey Bakhurin
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* Digital Signal Processing Library [http://dsplib.org]
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*
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* This file is part of libdspl-2.0.
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*
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* is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser 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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* DSPL 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 Lesser General Public License
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* along with Foobar. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <stdlib.h>
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#include <string.h>
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#include <math.h>
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#include "dspl.h"
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#ifdef DOXYGEN_ENGLISH
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/*! ****************************************************************************
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\ingroup DFT_GROUP
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\brief Time signal reconstruction from Fourier series coefficients.
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Function reconstructs the time signal:
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\f[
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s(t) = \sum\limits_{n = 0}^{n_{\omega}-1} S(\omega_n) \exp(j\omega_n t)
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\f]
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\param[in] w
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Pointer to the Fourier series spectrum frequency vector \f$\omega_n\f$. \n
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Vector size is `[nw x 1]`. \n
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\n
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\param[in] s
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Pointer to the Fourier series coefficients vector \f$S(\omega_n)\f$. \n
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Vector size is `[nw x 1]`. \n
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\n
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\param[in] nw
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Number of Fourier series coefficients. \n
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This value must be positive. \n
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\n
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\param[in] t
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Pointer to the reconstructed signal time vector. \n
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Vector size is `[nt x 1]`. \n
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\n
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\param[in] nt
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Size of time vector and reconstructed signal vector . \n
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\n
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\param[out] y
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Pointer to the reconstructed signal vector. \n
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Vector size is `[nt x 1]`. \n
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Memory must be allocated. \n
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\n
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\return
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`RES_OK` if function is calculated successfully. \n
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Else \ref ERROR_CODE_GROUP "code error".
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\note
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The output reconstructed signal is generally complex.
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However, subject to the symmetry properties of the vectors `w` and` s`
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with respect to zero frequency we get the imaginary part of the vector `y`
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at the EPS level. The negligible imaginary part in this case
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can be ignored.
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\n
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\author Sergey Bakhurin www.dsplib.org
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***************************************************************************** */
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#endif
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#ifdef DOXYGEN_RUSSIAN
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/*! ****************************************************************************
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\ingroup DFT_GROUP
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\brief Восстановление сигнала при усечении ряда Фурье
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Функция рассчитывает восстановленный сигнал при усечении ряда Фурье:
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\f[
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s(t) = \sum\limits_{n = 0}^{n_{\omega}-1} S(\omega_n) \exp(j\omega_n t)
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\f]
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\param[in] w
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Указатель на массив частот \f$\omega_n\f$ усеченного ряда Фурье. \n
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Размер вектора `[nw x 1]`. \n
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Память должна быть выделена и заполнена. \n
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\n
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\param[in] s
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Указатель на массив значений спектра \f$S(\omega_n)\f$. \n
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Размер вектора `[nw x 1]`. \n
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Память должна быть выделена и заполнена. \n
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\n
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\param[in] nw
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Количество членов усеченного ряда Фурье. \n
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Значение должно быть положительным. \n
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\n
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\param[in] t
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Указатель на массив временных отсчетов восстановленного сигнала. \n
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Размер вектора `[nt x 1]`. \n
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Память должна быть выделена и заполнена. \n
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\n
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\param[in] nt
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Размер вектора времени и восстановленного сигнала. \n
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\n
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\param[out] y
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Указатель на массив восстановленного сигнала. \n
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Размер вектора `[nt x 1]`. \n
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Память должна быть выделена. \n
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\n
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\return
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`RES_OK` --- восстановление сигнала прошло успешно. \n
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В противном случае \ref ERROR_CODE_GROUP "код ошибки". \n
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\note
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Выходной восстановленный сигнал в общем случае является комплексным.
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Однако при соблюдении свойств симметрии векторов `w` и `s` относительно
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нулевой частоты получим мнимую часть элементов вектора `y` на уровне ошибок
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округления числа с двойной точностью. Ничтожно малую мнимую часть в этом случае
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можно игнорировать.
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\n
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\author Бахурин Сергей www.dsplib.org
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***************************************************************************** */
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#endif
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int DSPL_API fourier_series_rec(double* w, complex_t* s, int nw,
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double* t, int nt, complex_t* y)
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{
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int k, m;
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complex_t e;
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if(!t || !s || !w || !y)
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return ERROR_PTR;
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if(nt<1 || nw < 1)
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return ERROR_SIZE;
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memset(y, 0, nt*sizeof(complex_t));
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for(k = 0; k < nw; k++)
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{
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for(m = 0; m < nt; m++)
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{
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RE(e) = cos(w[k] * t[m]);
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IM(e) = sin(w[k] * t[m]);
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RE(y[m]) += CMRE(s[k], e);
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IM(y[m]) += CMIM(s[k], e);
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}
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}
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return RES_OK;
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}
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