kopia lustrzana https://github.com/Dsplib/libdspl-2.0
231 wiersze
6.9 KiB
C
231 wiersze
6.9 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 cheby1_ap(double Rp, int ord, double* b, double* a)
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\brief
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Function calculates the transfer function \f$ H(s) \f$ coefficients of
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analog normalized lowpass Chebyshev type 1 filter.
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Analog normalized lowpass filter magnitude ripple equals \f$ -R_p \f$ dB
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for angular frequency \f$ \omega \f$ from 0 to 1 rad/s.
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\param[in] Rp
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Magnitude ripple in passband (dB). \n
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This parameter sets maximum filter distortion from 0 to 1 rad/s frequency. \n
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Parameter must be positive. \n
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\n
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\param[in] ord
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Filter order. \n
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Filter coefficients number equals `ord+1` for numerator and denominator
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of transfer function \f$ H(s) \f$ \n
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\n
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\param[out] b
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Pointer to the vector of transfer function \f$H(s)\f$
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numerator coefficient. \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[out] a
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Pointer to the vector of transfer function \f$H(s)\f$
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denominator coefficient. \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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\n
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Example:
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\include cheby1_ap_test.c
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Result:
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\verbatim
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b[ 0] = 0.125 a[ 0] = 0.177
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b[ 1] = 0.000 a[ 1] = 0.405
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b[ 2] = 0.000 a[ 2] = 1.169
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b[ 3] = 0.000 a[ 3] = 0.582
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b[ 4] = 0.000 a[ 4] = 1.000
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\endverbatim
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\n
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In `dat` folder will be created 3 files: \n
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\verbatim
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cheby1_ap_test_mag.txt magnitude
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cheby1_ap_test_phi.txt phase response
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cheby1_ap_test_tau.txt group delay
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\endverbatim
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In addition, GNUPLOT will build the following graphs from data stored in files:
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\image html cheby1_ap_test.png
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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 cheby1_ap(double Rp, int ord, double* b, double* a)
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\brief
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Расчет передаточной характеристики \f$ H(s) \f$ аналогового
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нормированного ФНЧ Чебышёва первого рода.
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Функция рассчитывает коэффициенты передаточной характеристики
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\f$ H(s)\f$ аналогового нормированного ФНЧ Чебышёва первого рода
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порядка `ord` с частотой среза 1 рад/с по уровню \f$-R_p\f$ дБ. \n
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Особенностью фильтра Чебышёва первого рода являются
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равноволновые пульсации АЧХ в полосе пропускания.
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\param[in] Rp
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Неравномерность АЧХ в полосе пропускания (дБ). \n
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Параметр задает уровень искажений в полосе от 0 до 1 рад/с. \n
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Значение должно быть положительным. \n
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\n
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\param[in] ord
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Порядок фильтра. \n
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Количество коэффициентов числителя и знаменателя
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передаточной функции \f$ H(s)\f$ равно `ord+1`. \n
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\n
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\param[out] b
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Указатель на вектор коэффициентов числителя передаточной функции \f$H(s)\f$. \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[out] a
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Указатель на вектор коэффициентов знаменателя
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передаточной функции \f$H(s)\f$. \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` --- фильтр рассчитан успешно. \n
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В противном случае \ref ERROR_CODE_GROUP "код ошибки". \n
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\n
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Пример использования функции `cheby1_ap`:
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\include cheby1_ap_test.c
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Результат работы программы:
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\verbatim
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b[ 0] = 0.125 a[ 0] = 0.177
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b[ 1] = 0.000 a[ 1] = 0.405
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b[ 2] = 0.000 a[ 2] = 1.169
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b[ 3] = 0.000 a[ 3] = 0.582
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b[ 4] = 0.000 a[ 4] = 1.000
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\endverbatim
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\n
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В каталоге `dat` будут созданы три файла: \n
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\verbatim
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cheby1_ap_test_mag.txt АЧХ фильтра
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cheby1_ap_test_phi.txt ФЧХ фильтра
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cheby1_ap_test_tau.txt ГВЗ фильтра
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\endverbatim
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\n
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Кроме того программа GNUPLOT произведет построение следующих графиков
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по сохраненным в файлах данным:
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\image html cheby1_ap_test.png
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\author
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Бахурин Сергей
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www.dsplib.org
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***************************************************************************** */
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#endif
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int DSPL_API cheby1_ap(double rp, int ord, double* b, double* a)
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{
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int res;
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complex_t *z = NULL;
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complex_t *p = NULL;
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int nz, np, k;
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complex_t h0 = {1.0, 0.0};
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double tmp;
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if(rp < 0.0)
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return ERROR_FILTER_RP;
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if(ord < 1)
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return ERROR_FILTER_ORD;
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if(!a || !b)
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return ERROR_PTR;
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z = (complex_t*) malloc(ord*sizeof(complex_t));
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p = (complex_t*) malloc(ord*sizeof(complex_t));
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res = cheby1_ap_zp(ord, rp, z, &nz, p, &np);
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if(res != RES_OK)
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goto exit_label;
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res = filter_zp2ab(z, nz, p, np, ord, b, a);
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if(res != RES_OK)
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goto exit_label;
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if(!(ord % 2))
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RE(h0) = 1.0 / pow(10.0, rp*0.05);
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for(k = 0; k < np; k++)
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{
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tmp = CMRE(h0, p[k]);
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IM(h0) = CMIM(h0, p[k]);
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RE(h0) = tmp;
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}
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b[0] = fabs(RE(h0));
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exit_label:
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if(z)
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free(z);
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if(p)
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free(p);
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return res;
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}
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