energy of a signal in t and f domain
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The energy of a signal is expected to be the same in t and f domain.
n = 1e4;
dx = 0.25;
x = rand(n,1) -0.5;
ex = sum(x.^2) *dx; % energy in t domain
y = fft(x);
fs = 1/dx;
df = fs/n;
ya = abs(y);
ey = sum(ya.^2) *df; % energy in f domain
but from the code, ey/ex=16, exactly the squared fs.
what's the problem?
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Accepted Answer
Star Strider
on 3 Dec 2014
You need to normalise the fft by dividing it by the length of the signal:
y = fft(x)/length(x);
See the documentation for fft for details.
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