Normally, when we dealing with power signal in frequency domain we usually use power spectral density.(adsbygoogle = window.adsbygoogle || []).push({});

My question is why is that? Why we define the power P(f) this way.

http://img21.imageshack.us/img21/6786/powerec.jpg [Broken]

This makes no sense to me, Why don't we just Fourier transform p(t) therefore we also get P(f)

http://img198.imageshack.us/img198/8603/power2a.jpg [Broken]

I just don't get the concept of power spectral density.

Please help!

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# Power spectral density question

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