dsp.INVERSE DISCRETE FOURIER TRANSFORM(IDFT)--------------- This program computes the IDFT of N point X(k).

  /*-------------INVERSE DISCRETE FOURIER TRANSFORM(IDFT)---------------
   This program computes the IDFT of N point X(k).

   Inputs: 1) Length of DFT i.e. N.
  2) Real and imaginary parts of DFT X(k).
   Outputs: N point sequence i.e. x(n).

   Assumptions: The sequence x(n) is considered real.
 =======================================================================*/

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

void main()
{
 float static X[100],X_Real[100],X_Imag[100];
 float k,n,N;
 clrscr();

 printf("\t\t\t Inverse Discrete Fourier Transform(IDFT)");
 printf("\n\n Enter the length of DFT N=");
 scanf("%f",&N);

 printf("\n Enter the real and imaginary parts of X(k) as follows:\n\n"
"X(k) =Real{X(k)} Img{X(k)} \n" );

 for(k=0;k<N;k++)
 {
  printf("X(%1.0f)=",k);
  scanf("%f%f",&X_Real[k],&X_Imag[k]);
 }

 for(n=0;n<N;n++)
 {
  X[n]=0;
  for(k=0;k<N;k++)
  {
   X[n]=X[n]+X_Real[k]*cos((2*M_PI*k*n)/N)-X_Imag[k]*sin((2*M_PI*k*n)/N);
  }
  X[n]=X[n]/N;
 }

 printf("\n\n The sequence x(n) is as follows...");
 for(n=0;n<N;n++)
 {
  printf("\n\n X(%1.0f)=%3.6f",n,X[n]);
 }

 getch();
}

***op********                   Inverse Discrete Fourier Transform(IDFT)

 Enter the length of DFT N=4

 Enter the real and imaginary parts of X(k) as follows:

 X(k) =Real{X(k)} Img{X(k)}

 X(0) =      4     0

 X(1) =      1    -1

 X(2) =     -2     0

 X(3) =      1     1


 The sequence x(n) is as follows...

 X(0)=1.000000

 X(1)=2.000000

 X(2)=-0.000000

 X(3)=1.000000