# spectrum for a communication signal [closed]

I have a communication signal.

Its bandwidth is limited. But does the $$X(f)$$ value is important? For example, I have $$X(f)=6.10^3$$ but for an other signal I have $$X(f)=10^6$$ (the channel is the same for the 2 signals).

## closed as unclear what you're asking by Dilip Sarwate, lennon310, A_A, Matt L., Stanley PawlukiewiczJan 18 at 19:29

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• Look up Parseval's theorem. – MBaz Jan 14 at 21:01
• X(f) = constant contradicts the plot you're showing. – Marcus Müller Jan 14 at 23:17

$$X$$ is not constant, as shown in the plot. But if you are asking about two signals with the same bandwidth but different magnitudes of Fourier transform, then it simply means they carry different amounts of energy, where energy is given by:
$$E = \int_{-\infty}^{+\infty} |X(f)|^2 d f,$$ which for a bandlimited signal has the cutoff frequencies as the lower and upper bounds for the integral.