fourier transform of sine wave help

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yuvi
yuvi 2014-10-19
评论： Star Strider 2014-10-19
hi everyone,
i have this simple code of a wave in time domain and frequency domain.
can someone pls help me understand this line ???
ff = Fs*(-0.5:1/length(t):0.5-1/length(t)); <-----------
thanks !
the code :
f0 = 10;
Fs = 10*f0;
t = 0:1/Fs:1;
x = cos(2*pi*f0*t);
X = abs(fftshift(fft(x)));
ff = Fs*(-0.5:1/length(t):0.5-1/length(t));
plot(t,x);
plot(ff,X);

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回答（1 个）

Star Strider
Star Strider 2014-10-19
It is coding for a two-sided (symmetric) Fourier series of the signal created in x. That is in keeping with the use of the fftshift function to define ‘X’.
  2 个评论
yuvi
yuvi 2014-10-19
Thanks Star Strider for your answer !
I need to understand this line particularly.
What is the meaning of 0.5 and -0.5 and length of t....
Thanks !
Star Strider
Star Strider 2014-10-19
My pleasure!
Putting this in context, ‘Fs’ is 100, ‘t’ goes from 0 to 1 in increments of 0.01 with a length of 101. The 0.5 (actually Fs*0.5) defines ‘ff’ to go from -50 to +50 in increments of 1/101.

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