kopia lustrzana https://github.com/Dsplib/libdspl-2.0
231 wiersze
7.4 KiB
C
231 wiersze
7.4 KiB
C
|
/*
|
|||
|
* Copyright (c) 2015-2019 Sergey Bakhurin
|
|||
|
* Digital Signal Processing Library [http://dsplib.org]
|
|||
|
*
|
|||
|
* This file is part of libdspl-2.0.
|
|||
|
*
|
|||
|
* is free software: you can redistribute it and/or modify
|
|||
|
* it under the terms of the GNU Lesser General Public License as published by
|
|||
|
* the Free Software Foundation, either version 3 of the License, or
|
|||
|
* (at your option) any later version.
|
|||
|
*
|
|||
|
* DSPL is distributed in the hope that it will be useful,
|
|||
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|||
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|||
|
* GNU General Public License for more details.
|
|||
|
*
|
|||
|
* You should have received a copy of the GNU Lesser General Public License
|
|||
|
* along with Foobar. If not, see <http://www.gnu.org/licenses/>.
|
|||
|
*/
|
|||
|
|
|||
|
#include <stdlib.h>
|
|||
|
#include <string.h>
|
|||
|
#include "dspl.h"
|
|||
|
|
|||
|
|
|||
|
#ifdef DOXYGEN_ENGLISH
|
|||
|
/*! ****************************************************************************
|
|||
|
\ingroup FILTER_CONV_GROUP
|
|||
|
\fn int filter_iir(double* b, double* a, int ord, double* x, int n, double* y)
|
|||
|
\brief Real IIR filtration
|
|||
|
|
|||
|
Function calculates real IIR filter output for real signal. The real filter
|
|||
|
contains real coefficients of the transfer function \f$H(z)\f$
|
|||
|
numerator and denominator:
|
|||
|
\f[
|
|||
|
H(z) = \frac{\sum_{n = 0}^{N} b_n z^{-n}}
|
|||
|
{1+{\frac{1}{a_0}}\sum_{m = 1}^{M} a_m z^{-n}},
|
|||
|
\f]
|
|||
|
here \f$a_0\f$ cannot be equals zeros, \f$N=M=\f$`ord`.
|
|||
|
|
|||
|
\param[in] b
|
|||
|
Pointer to the vector \f$b\f$ of IIR filter
|
|||
|
transfer function numerator coefficients. \n
|
|||
|
Vector size is `[ord + 1 x 1]`. \n \n
|
|||
|
|
|||
|
\param[in] a
|
|||
|
Pointer to the vector \f$a\f$ of IIR filter
|
|||
|
transfer function denominator coefficients. \n
|
|||
|
Vector size is `[ord + 1 x 1]`. \n
|
|||
|
This pointer can be `NULL` if filter is FIR. \n \n
|
|||
|
|
|||
|
\param[in] ord
|
|||
|
Filter order. Number of the transfer function
|
|||
|
numerator and denominator coefficients
|
|||
|
(length of vectors `b` and `a`) is `ord + 1`. \n \n
|
|||
|
|
|||
|
\param[in] x
|
|||
|
Pointer to the input signal vector. \n
|
|||
|
Vector size is `[n x 1]`. \n \n
|
|||
|
|
|||
|
\param[in] n
|
|||
|
Size of the input signal vector `x`. \n \n
|
|||
|
|
|||
|
\param[out] y
|
|||
|
Pointer to the IIR filter output vector. \n
|
|||
|
Vector size is `[n x 1]`. \n
|
|||
|
Memory must be allocated. \n \n
|
|||
|
|
|||
|
\return
|
|||
|
`RES_OK` if filter output is calculated successfully. \n
|
|||
|
Else \ref ERROR_CODE_GROUP "code error". \n
|
|||
|
|
|||
|
Example:
|
|||
|
|
|||
|
\include filter_iir_test.c
|
|||
|
|
|||
|
Input signal is
|
|||
|
\f$s(t) = \sin(2\pi \cdot 0.05 t) + n(t)\f$, here \f$n(t)\f$ white Gaussian
|
|||
|
noise with zero mean value and unit standard deviation. \n
|
|||
|
|
|||
|
Input signal is filtered by elliptic LPF order 6 and output signal and data
|
|||
|
saves in the txt-files
|
|||
|
|
|||
|
\verbatim
|
|||
|
dat/s.txt - input signal + noise
|
|||
|
dat/sf.txt - filter output.
|
|||
|
\endverbatim
|
|||
|
|
|||
|
Plots:
|
|||
|
|
|||
|
\image html filter_iir_test.png
|
|||
|
|
|||
|
GNUPLOT script for make plots is:
|
|||
|
\include filter_iir.plt
|
|||
|
|
|||
|
\author Sergey Bakhurin www.dsplib.org
|
|||
|
***************************************************************************** */
|
|||
|
#endif
|
|||
|
#ifdef DOXYGEN_RUSSIAN
|
|||
|
/*! ****************************************************************************
|
|||
|
\ingroup FILTER_CONV_GROUP
|
|||
|
\fn int filter_iir(double* b, double* a, int ord, double* x, int n, double* y)
|
|||
|
\brief Фильтрация вещественного сигнала вещественным БИХ-фильтром
|
|||
|
|
|||
|
Функция рассчитывает выход фильтра заданного выражением
|
|||
|
\f[
|
|||
|
H(z) = \frac{\sum_{n = 0}^{N} b_n z^{-n}}
|
|||
|
{1+{\frac{1}{a_0}}\sum_{m = 1}^{M} a_m z^{-m}},
|
|||
|
\f]
|
|||
|
где \f$a_0\f$ не может быть 0, \f$N=M=\f$`ord`.
|
|||
|
|
|||
|
\param[in] b
|
|||
|
Указатель на вектор коэффициентов числителя
|
|||
|
передаточной функции \f$H(z)\f$ БИХ-фильтра. \n
|
|||
|
Размер вектора `[ord + 1 x 1]`. \n \n
|
|||
|
|
|||
|
\param[in] a
|
|||
|
Указатель на вектор коэффициентов знаменателя
|
|||
|
передаточной функции \f$H(z)\f$ БИХ-фильтра. \n
|
|||
|
Размер вектора `[ord + 1 x 1]`. \n
|
|||
|
Этот указатель может быть `NULL`, тогда фильтрация производится
|
|||
|
без использования рекурсивной части
|
|||
|
(вектор коэффициентов `b` задает КИХ-фильтр). \n \n
|
|||
|
|
|||
|
\param[in] ord
|
|||
|
Порядок фильтра. Количество коэффициентов числителя и знаменателя
|
|||
|
передаточной функции \f$H(z)\f$ БИХ-фильтра равно `ord + 1`. \n \n
|
|||
|
|
|||
|
\param[in] x
|
|||
|
Указатель на вектор отсчетов входного сигнала. \n
|
|||
|
Размер вектора `[n x 1]`. \n \n
|
|||
|
|
|||
|
\param[in] n
|
|||
|
Длина входного сигнала. \n \n
|
|||
|
|
|||
|
\param[out] y
|
|||
|
Указатель на вектор выходных отсчетов фильтра. \n
|
|||
|
Размер вектора `[n x 1]`. \n
|
|||
|
Память должна быть выделена заранее. \n \n
|
|||
|
|
|||
|
\return
|
|||
|
`RES_OK` Если фильтрация произведена успешно. \n
|
|||
|
В противном случае \ref ERROR_CODE_GROUP "код ошибки". \n
|
|||
|
|
|||
|
Пример использования функции `filter_iir`:
|
|||
|
|
|||
|
\include filter_iir_test.c
|
|||
|
|
|||
|
На входе цифрового фильтра задан сигнал
|
|||
|
\f$s(t) = \sin(2\pi \cdot 0.05 t) + n(t)\f$, где \f$n(t)\f$ белый гауссовский
|
|||
|
шум, с нулевым средним и единичной дисперсией. \n
|
|||
|
Фильтр представляет собой эллиптический ФНЧ 6 порядка.
|
|||
|
Входной сигнал фильтруется данным фильтром, и результат сохраняется в файлы:
|
|||
|
|
|||
|
\verbatim
|
|||
|
dat/s.txt - исходный зашумленный сигнал
|
|||
|
dat/sf.txt - сигнал на выходе фильтра.
|
|||
|
\endverbatim
|
|||
|
|
|||
|
По полученным данным производится построение графиков:
|
|||
|
|
|||
|
\image html filter_iir_test.png
|
|||
|
|
|||
|
\author Бахурин Сергей www.dsplib.org
|
|||
|
***************************************************************************** */
|
|||
|
#endif
|
|||
|
int DSPL_API filter_iir(double* b, double* a, int ord,
|
|||
|
double* x, int n, double* y)
|
|||
|
{
|
|||
|
double *buf = NULL;
|
|||
|
double *an = NULL;
|
|||
|
double *bn = NULL;
|
|||
|
double u;
|
|||
|
int k;
|
|||
|
int m;
|
|||
|
int count;
|
|||
|
|
|||
|
if(!b || !x || !y)
|
|||
|
return ERROR_PTR;
|
|||
|
|
|||
|
if(ord < 1 || n < 1)
|
|||
|
return ERROR_SIZE;
|
|||
|
|
|||
|
if(a && a[0]==0.0)
|
|||
|
return ERROR_FILTER_A0;
|
|||
|
|
|||
|
count = ord + 1;
|
|||
|
buf = (double*) malloc(count*sizeof(double));
|
|||
|
an = (double*) malloc(count*sizeof(double));
|
|||
|
|
|||
|
memset(buf, 0, count*sizeof(double));
|
|||
|
|
|||
|
if(!a)
|
|||
|
{
|
|||
|
memset(an, 0, count*sizeof(double));
|
|||
|
bn = b;
|
|||
|
}
|
|||
|
else
|
|||
|
{
|
|||
|
bn = (double*) malloc(count*sizeof(double));
|
|||
|
for(k = 0; k < count; k++)
|
|||
|
{
|
|||
|
an[k] = a[k] / a[0];
|
|||
|
bn[k] = b[k] / a[0];
|
|||
|
}
|
|||
|
}
|
|||
|
|
|||
|
for(k = 0; k < n; k++)
|
|||
|
{
|
|||
|
for(m = ord; m > 0; m--)
|
|||
|
buf[m] = buf[m-1];
|
|||
|
u = 0.0;
|
|||
|
for(m = ord; m > 0; m--)
|
|||
|
u += buf[m]*an[m];
|
|||
|
|
|||
|
buf[0] = x[k] - u;
|
|||
|
y[k] = 0.0;
|
|||
|
for(m = 0; m < count; m++)
|
|||
|
y[k] += buf[m] * bn[m];
|
|||
|
}
|
|||
|
|
|||
|
if(buf)
|
|||
|
free(buf);
|
|||
|
if(an)
|
|||
|
free(an);
|
|||
|
if(bn && (bn != b))
|
|||
|
free(bn);
|
|||
|
return RES_OK;
|
|||
|
}
|
|||
|
|