Hi, Folks:

I am curious about how machine spectrum analyzer calculate the PSD of input signal.

In Parcevall law:

Integrate (f(t)^2) = Integrate (F(s)^2) ;

In left side of equation, original law said that the integration start from -T to +T.  (T is measurement interval)

However, in real world, f(t) is always zero when time is negative.

So, the final PSD is get from divide both sides by T, or 2T? I think it should be T, is that right?