kopia lustrzana https://github.com/Dsplib/libdspl-2.0
169 wiersze
5.8 KiB
C
169 wiersze
5.8 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 <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "dspl.h"
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#ifdef DOXYGEN_ENGLISH
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/*! ****************************************************************************
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\ingroup IIR_FILTER_DESIGN_GROUP
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\fn int low2high (double* b, double* a, int ord, double w0, double w1,
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double* beta, double* alpha)
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\brief Lowpass to highpass filter frequency transform
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Function transforms lowpass filter transfer function \f$ H(s) \f$
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to the highpass filter transfer function \f$ F(s) \f$.
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Filter order, magnitude ripple in passband and stopband
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supression still the same.
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\param[in] b
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Pointer to the lowpass filter transfer function \f$H(s)\f$ numerator
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coefficients vector. \n
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Vector size is `[ord+1 x 1]`. \n
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\n
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\param[in] a
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Pointer to the lowpass filter transfer function \f$H(s)\f$ denominator
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coefficients vector. \n
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Vector size is `[ord+1 x 1]`. \n
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\n
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\param[in] ord
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Filter order. \n
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\n
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\param[in] w0
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Lowpass filter cutoff frequency. \n
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\n
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\param[in] w1
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Highpass filter cutoff frequency after transformation. \n
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\n
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\param[in,out] beta
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Pointer to the highwpass filter transfer function \f$F(s)\f$ numerator
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coefficients vector after transformation. \n
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Vector size is `[ord+1 x 1]`. \n
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Memory must be allocated. \n
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\n
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\param[in,out] alpha
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Pointer to the highwpass filter transfer function \f$F(s)\f$ denominator
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coefficients vector after transformation. \n
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Vector size is `[ord+1 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 filter coefficients is calculated successfully. \n
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Else \ref ERROR_CODE_GROUP "code error".
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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 IIR_FILTER_DESIGN_GROUP
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\fn int low2high (double* b, double* a, int ord, double w0, double w1,
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double* beta, double* alpha)
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\brief Частотное преобразование ФНЧ-ФВЧ
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Функция производит перобразование передаточной функции \f$ H(s) \f$
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аналогового ФНЧ с частотой среза `w0` рад/c
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в передаточную функцию \f$ F(s) \f$ аналоговго ФВЧ с частотой среза `w1` рад/c.
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Неравномерность АЧХ в полосе пропускания, уровень подавления в полосе
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заграждения и порядок фильтра остаются неизменными.
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\param[in] b
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Указатель на вектор коэффициентов числителя передаточной функции \f$H(s)\f$
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исходного аналогового ФНЧ. \n
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Размер вектора `[ord+1 x 1]`. \n
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Память должна быть выделена. \n
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\n
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\param[in] a
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Указатель на вектор коэффициентов знаменателя передаточной функции \f$H(s)\f$
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исходного аналогового ФНЧ. \n
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Размер вектора `[ord+1 x 1]`. \n
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Память должна быть выделена. \n
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\n
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\param[in] ord
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Порядок исходного фильтра и фильтра после переобразования. \n
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\n
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\param[in] w0
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Частота среза исходного ФНЧ. \n
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\n
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\param[in] w1
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Требуемая частота среза ФВЧ после преобразования. \n
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\n
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\param[in,out] beta
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Указатель на вектор коэффициентов числителя передаточной функции \f$F(s)\f$
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ФВЧ после преобразования. \n
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Размер вектора `[ord+1 x 1]`. \n
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Память должна быть выделена. \n
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\n
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\param[in,out] alpha
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Указатель на вектор коэффициентов знаменателя передаточной функции \f$F(s)\f$
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аналогового ФВЧ после преобразования. \n
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Размер вектора `[ord+1 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` --- преобразование рассчитано успешно. \n
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В противном случае \ref ERROR_CODE_GROUP "код ошибки". \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 low2high(double* b, double* a, int ord, double w0, double w1,
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double* beta, double* alpha)
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{
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double num[2] = {0.0, 0.0};
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double den[2] = {0.0, 1.0};
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if(!b || !a || !beta || !alpha)
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return ERROR_PTR;
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if(ord < 1)
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return ERROR_FILTER_ORD;
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if(w0 <= 0.0 || w1 <= 0.0)
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return ERROR_FILTER_FT;
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num[0] = w1 / w0;
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return ratcompos(b, a, ord, num, den, 1, beta, alpha);
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}
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