iir matlab c代码,[数字信号处理]IIR滤波器的直接设计(C代码)

以下是一个基于Matlab的IIR滤波器直接设计算法的C代码实现：

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#define PI  3.14159265358979323846

//定义IIR滤波器结构体
typedef struct
{
    int order;      //滤波器阶次
    double *a;      //分母系数
    double *b;      //分子系数
    double *x;      //历史输入值
    double *y;      //历史输出值
}IIR_Filter;

//IIR滤波器初始化函数
void IIR_Filter_Init(IIR_Filter *filter, int order, double *a, double *b)
{
    int i;

    filter->order = order;
    filter->a = (double *)malloc((order + 1) * sizeof(double));
    filter->b = (double *)malloc((order + 1) * sizeof(double));
    filter->x = (double *)malloc((order + 1) * sizeof(double));
    filter->y = (double *)malloc((order + 1) * sizeof(double));

    for (i = 0; i <= order; i++)
    {
        filter->a[i] = a[i];
        filter->b[i] = b[i];
        filter->x[i] = 0.0;
        filter->y[i] = 0.0;
    }
}

//IIR滤波器处理函数
double IIR_Filter_Process(IIR_Filter *filter, double input)
{
    int i;
    double output = 0.0;

    //更新历史输入值和历史输出值
    for (i = filter->order; i >= 1; i--)
    {
        filter->x[i] = filter->x[i - 1];
        filter->y[i] = filter->y[i - 1];
    }
    filter->x[0] = input;

    //计算滤波器输出
    for (i = 0; i <= filter->order; i++)
    {
        output += filter->b[i] * filter->x[i];
    }
    for (i = 1; i <= filter->order; i++)
    {
        output -= filter->a[i] * filter->y[i];
    }
    output /= filter->a[0];

    filter->y[0] = output;

    return output;
}

int main()
{
    int i;
    int order = 2;
    double a[3] = { 1.0, -1.1430, 0.4128 };
    double b[3] = { 0.2063, 0.4125, 0.2063 };
    double input[10] = { 0.5, 0.2, -0.4, 0.8, -0.6, 0.9, -0.3, 0.5, -0.2, 0.3 };
    IIR_Filter *filter;
    double output;

    filter = (IIR_Filter *)malloc(sizeof(IIR_Filter));

    IIR_Filter_Init(filter, order, a, b);

    for (i = 0; i < 10; i++)
    {
        output = IIR_Filter_Process(filter, input[i]);
        printf("input = %f, output = %f\n", input[i], output);
    }

    free(filter->a);
    free(filter->b);
    free(filter->x);
    free(filter->y);
    free(filter);

    return 0;
}

其中，IIR_Filter_Init函数用于初始化IIR滤波器结构体，IIR_Filter_Process函数用于处理输入信号并返回滤波器的输出信号。在main函数中，首先定义了一个二阶IIR滤波器，然后输入了一个长度为10的信号，通过IIR滤波器处理后输出滤波器的输出信号。