Fourier transform of a power signal or a voltage signal

[Jiho]

Homework Statement

By using Fourier transform, I want to calculate power of signal. I confuse that f(x) in attached equation represents voltage or power. Is that possible when f(x) means power to use Fourier transform.

Homework Equations

The Attempt at a Solution

 

[RPinPA]

In all of those equations, $x(t)$ is your original signal (not its power) and $X(f)$ or $X_n$ refer to the Fourier transform of $x(t)$. Take the absolute value AFTER you Fourier Transform.