我在这里贴出一份FIR数字滤波器C程序，愿有兴趣的前来指点。


#include "myapp.h"
#include "csedu.h"
#include "scancode.h"
#include <math.h>
#define FIRNUMBER 25
#define SIGNAL1F 1000
#define SIGNAL2F 4500
#define SAMPLEF  10000
#define PI 3.1415926
float InputWave();
float FIR();
float fHn[FIRNUMBER]={ 0.0,0.0,0.001,-0.002,-0.002,0.01,-0.009,
                       -0.018,0.049,-0.02,0.11,0.28,0.64,0.28,
                       -0.11,-0.02,0.049,-0.018,-0.009,0.01,
                       -0.002,-0.002,0.001,0.0,0.0
                     };
float fXn[FIRNUMBER]={ 0.0 };
float fInput,fOutput;
float fSignal1,fSignal2;
float fStepSignal1,fStepSignal2;
float f2PI;
int i;
float fIn[256],fOut[256];
int nIn,nOut;
main()
{
nIn=0; nOut=0;
f2PI=2*PI;
fSignal1=0.0;
fSignal2=PI*0.1;
fStepSignal1=2*PI/30;
fStepSignal2=2*PI*1.4;
while ( 1 )
{
  fInput=InputWave();
  fIn[nIn]=fInput;
  nIn++; nIn%=256;
  fOutput=FIR();
  fOut[nOut]=fOutput;
  nOut++;    /* break point */
  if ( nOut>=256 )
  {
   nOut=0;  
  }
}
}
float InputWave()
{
for ( i=FIRNUMBER-1;i>0;i-- )
  fXn[i]=fXn[i-1];//移一位
fXn[0]=sin((double)fSignal1)+cos((double)fSignal2)/6.0;//增加一值
fSignal1+=fStepSignal1;
if ( fSignal1>=f2PI ) fSignal1-=f2PI;
fSignal2+=fStepSignal2;
if ( fSignal2>=f2PI ) fSignal2-=f2PI;
return(fXn[0]);
}
float FIR()
{
float fSum;
fSum=0;
for ( i=0;i<FIRNUMBER;i++ )
{
  fSum+=(fXn[i]*fHn[i]);
}
return(fSum);
}