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Discrete Fourier Transforms without using FFT function

  1. Nov 5, 2011 #1
    This is what I have done so far
    Code (Text):

    t = -5:.01:4.99;   // this give us our rect function from -.5 to .5
    x = abs(t) <= .5;
    subplot(2,1,1)     // creates a subplot for the rect function
    plot(t,x)
    axis([-2 2 -1 2])  // sets the axis

    T_s = .001;       // The calculation of the discrete Fourier Transform
    F_s = 1./T_s;
    N = 1000;
    n = -N/2.:1.:(N/2.)-1;
    f = -F_s/2.:1.:(F_s/2.)-1;

    X_f = T_s*x*exp(-1i*2*pi*f'*n*T_s);

    z = fft(X_f);
    subplot(2,1,2)
    plot(abs(X_f))
     
    Here is the the formula for the Fourier transform. I expect to get a sinc function, which I am but it doesn't match it by scale.

    [PLAIN]http://img580.imageshack.us/img580/1699/fourier.jpg [Broken]
     
    Last edited by a moderator: May 5, 2017
  2. jcsd
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