kopia lustrzana https://github.com/Dsplib/libdspl-2.0
191 wiersze
6.0 KiB
C
191 wiersze
6.0 KiB
C
/*
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* Copyright (c) 2015-2019 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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\fn int fourier_series_dec(double* t, double* s, int nt, double period,
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int nw, double* w, complex_t* y)
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\brief
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Fourier series coefficient calculation for periodic signal
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\param[in] t
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Pointer to the 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] s
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Pointer to the signal corresponds to time `t`. \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 and signal vectors. \n
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This value must be positive. \n
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\n
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\param[in] period
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Signal time period. \n
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\n
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\param[in] nw
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Number of Fourie series coefficients. \n
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\n
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\param[out] w
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Pointer to the frequency vector (rad/s). \n
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Vector size is `[nw x 1]`. \n
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Memory must be allocated. \n
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\n
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\param[out] y
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Pointer to the complex Fourier series coefficients vector. \n
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Vector size is `[nw 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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Numerical integration is used for Fourier series coefficients calculation.
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This function is not effective.
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To increase the speed of calculation of the signal spectrum
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it is more expedient to use fast Fourier transform algorithms.
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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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\fn int fourier_series_dec(double* t, double* s, int nt, double period,
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int nw, double* w, complex_t* y)
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\brief
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Расчет коэффициентов разложения в ряд Фурье
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Функция рассчитывает спектр периодического сигнала при усечении ряда Фурье \n
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\param[in] t
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Указатель на массив моментов времени дискретизации исходного сигнала `s`. \n
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Размер вектора вектора `[nt x 1]`. \n
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Память должна быть выделена. \n
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\n
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\param[in] s
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Указатель на массив значений исходного сигнала`s`. \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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\param[in] nt
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Размер выборки исходного сигнала. \n
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Значение должно быть положительным. \n
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\n
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\param[in] period
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Период повторения сигнала. \n
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\n
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\param[in] nw
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Размер усеченного ряда Фурье. \n
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\n
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\param[out] w
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Указатель на массив частот спектра периодического сигнала. \n
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Размер вектора `[nw x 1]`. \n
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Память должна быть выделена. \n
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\n
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\param[out] y
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Указатель массив комплексных значений спектра периодического сигнала. \n
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Размер вектора `[nw 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` --- коэффициенты ряда Фурье рассчитаны 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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Для расчета спектра сигнала используется численное интегрирование
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исходного сигнала методом трапеций. Данная функция не является
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эффективной. Для увеличения скорости расчета спектра сигнала
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целесообразнее использовать алгоритмы дискретного
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и быстрого преобразования Фурье.
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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_dec(double* t, double* s, int nt, double period,
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int nw, double* w, complex_t* y)
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{
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int k, m;
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double dw = M_2PI / period;
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complex_t e[2];
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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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if(period <= 0.0)
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return ERROR_NEGATIVE;
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memset(y, 0 , nw*sizeof(complex_t));
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for(k = 0; k < nw; k++)
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{
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w[k] = (k - nw/2) * dw;
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RE(e[1]) = s[0] * cos(w[k] * t[0]);
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IM(e[1]) = -s[0] * sin(w[k] * t[0]);
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for(m = 1; m < nt; m++)
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{
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RE(e[0]) = RE(e[1]);
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IM(e[0]) = IM(e[1]);
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RE(e[1]) = s[m] * cos(w[k] * t[m]);
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IM(e[1]) = - s[m] * sin(w[k] * t[m]);
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RE(y[k]) += 0.5 * (RE(e[0]) + RE(e[1]))*(t[m] - t[m-1]);
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IM(y[k]) += 0.5 * (IM(e[0]) + IM(e[1]))*(t[m] - t[m-1]);
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}
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RE(y[k]) /= period;
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IM(y[k]) /= period;
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}
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if(!(nw%2))
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RE(y[0]) = RE(y[1]) = 0.0;
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return RES_OK;
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}
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