數字濾波的C實現

1. 用於對複數信號（I+jQ）做濾波；
2. 濾波器爲實數係數，奇數位數最佳；
3. 對標Matlab的conv(x,y,'valid')。

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

#define DATA_LEN    7
#define FILTER_LEN  3

typedef struct Complex_Double_Struct
{
    double      real;
    double      imag;
}COMPLEX_DOUBLE_STRUCT;


typedef struct Data_Struct
{
    unsigned int            data_length;
    COMPLEX_DOUBLE_STRUCT   data[DATA_LEN];
}DATA_STRUCT;

typedef struct Filter_Struct
{
    unsigned int    filter_length;
    double          filter_coef[FILTER_LEN];
}FILTER_STRUCT;

int Filter_Operation(const DATA_STRUCT *data_in,DATA_STRUCT *data_out,const FILTER_STRUCT *filter);


int main()
{
    DATA_STRUCT     data_in;
    DATA_STRUCT     data_out;
    FILTER_STRUCT   filter;
    memset((void*)&data_out,0,sizeof(data_out));

    data_in.data_length=DATA_LEN;
    data_in.data[0].real=1.0;
    data_in.data[0].imag=2.0;
    data_in.data[1].real=1.0;
    data_in.data[1].imag=-2.0;
    data_in.data[2].real=-1.0;
    data_in.data[2].imag=1.0;
    data_in.data[3].real=-1.0;
    data_in.data[3].imag=4.0;
    data_in.data[4].real=1.0;
    data_in.data[4].imag=0.0;
    data_in.data[5].real=2.0;
    data_in.data[5].imag=2.0;
    data_in.data[6].real=4.0;
    data_in.data[6].imag=2.0;
    filter.filter_length=FILTER_LEN;
    filter.filter_coef[0]=0.1;
    filter.filter_coef[1]=0.8;
    filter.filter_coef[2]=0.1;
    Filter_Operation(&data_in,&data_out,&filter);
    return 0;
}

int Filter_Operation(const DATA_STRUCT *data_in,DATA_STRUCT *data_out,const FILTER_STRUCT *filter)
{
    unsigned int            i=0;
    unsigned int            j=0;
    COMPLEX_DOUBLE_STRUCT   data_tmp;


    for(i=0;i<=(data_in->data_length)-(filter->filter_length);++i)
    {
        data_tmp.real=0;
        data_tmp.imag=0;
        for(j=i;j<i+filter->filter_length;++j)
        {
            data_tmp.real+=data_in->data[j].real*filter->filter_coef[j-i];
            data_tmp.imag+=data_in->data[j].imag*filter->filter_coef[j-i];
        }
        data_out->data[i].real=data_tmp.real;
        data_out->data[i].imag=data_tmp.imag;
    }

    data_out->data_length=data_in->data_length-filter->filter_length;

    return 0;
}

matlab 對標結果：