fft.cpp

这是有关数字信号处理的课程的源代码

#include<stdio.h>
#include<dos.h>
#include<stdlib.h>
#include<malloc.h>
#include<math.h>
#include"dsp.h"

void main()
{
  COMPLEX*x,*xtemp;
  int i,nn,mm;
  double y,q;

  system("cls");
  printf("\n********************************************");
  printf("\n*   Filename:fft1.c                        *");
  printf("\n*   Function:fft analysis for signals      *");
  printf("\n*   Signal  :x(n)=exp(-n)                  *");
  printf("\n********************************************");
  printf("\n Input m= ");
  scanf("%d",&mm);
  nn=1<<mm;
  x=(COMPLEX*)calloc(nn,sizeof(COMPLEX));
  xtemp=(COMPLEX*)calloc(nn,sizeof(COMPLEX));

  x[0].real=1.0;
  x[0].imag=0.0;
  for(i=1;i<nn;i++)
  {x[i].real=(float)exp(-i);
   x[i].imag=0.0;
  }
   for(i=0;i<nn;i++)xtemp[i]=x[i];







/* FFT analysis for x(n)  */
  fft(x,mm);
  printf("finished! \n\n");

  /*  output result in a format */

  printf(" k            XR(K)            XI(K)             |X(K)|              Q(K)\n");
  printf("------------------------------------------------------\n");
    for(i=0;i<nn;i++)
	{ 
		y=x[i].real*x[i].real+x[i].imag*x[i].imag;
      if(x[i].real!=0)
	  {
		  if(x[i].imag==0.0)
		  {  if(x[i].real>0) q=0.0;
             if(x[i].real<0) q=4.0*(atan(1.0));
		  }
  q=atan(x[i].imag/x[i].real);
   }
  printf("%2d        %7f         %9f         %9f         %9f\n",i,x[i].real,x[i].imag,sqrt(y),q);
  }
  printf("\n\n");
  }