- #1
sapz
- 33
- 1
Hello,
I'm trying to figure out a solution of a question I saw, I'll ask it here in this forum because perhaps this is where it belongs.
Let's say I have a Pulse wave that I am given it's frequency spectrum: [itex]B(w) = V_0\frac{Sin[(w-w_0)T]}{(w-w_0)T}[/itex] Where V0, T, w0 are constants.
So I do an inverse Fourier transform to get the actual wave, and I get:
[itex]B(t) = F^{-1}( B(w) ) = \frac{V_0}{T}\sqrt{\frac{\Pi}{2}}e^{-iw_0t}[Heaviside(t+T)-Heaviside(t-T)][/itex]
And now I'm asked, what is the intensity of the pulse for w=w0?
So the solution I've seen, claims that when w=w0, you get:
[itex]B(t)_{w=w_0} = B(w_0)Sin(w_0t)[/itex] (Where B(w0) is when you put w0 in B(w))
It states this without an explanation of why this is correct.
(And after you have that, you can find the intensity pretty easily, but its here that I get stuck)
To me, this statement ([itex]B_{w=w_0}(t) = B(w_0)Sin(w_0t)[/itex]) makes sense only if the entire wave B(t) was an odd function, because then it would comprise only of Sin waves.
And then, out of all the continuous values of w I could take only the one I'm interested in, which is w0, and putting it in B(w) would give me the amplitude of that specific wave.
How is this statement justified? Is B(t) an odd function?
I'm trying to figure out a solution of a question I saw, I'll ask it here in this forum because perhaps this is where it belongs.
Let's say I have a Pulse wave that I am given it's frequency spectrum: [itex]B(w) = V_0\frac{Sin[(w-w_0)T]}{(w-w_0)T}[/itex] Where V0, T, w0 are constants.
So I do an inverse Fourier transform to get the actual wave, and I get:
[itex]B(t) = F^{-1}( B(w) ) = \frac{V_0}{T}\sqrt{\frac{\Pi}{2}}e^{-iw_0t}[Heaviside(t+T)-Heaviside(t-T)][/itex]
And now I'm asked, what is the intensity of the pulse for w=w0?
So the solution I've seen, claims that when w=w0, you get:
[itex]B(t)_{w=w_0} = B(w_0)Sin(w_0t)[/itex] (Where B(w0) is when you put w0 in B(w))
It states this without an explanation of why this is correct.
(And after you have that, you can find the intensity pretty easily, but its here that I get stuck)
To me, this statement ([itex]B_{w=w_0}(t) = B(w_0)Sin(w_0t)[/itex]) makes sense only if the entire wave B(t) was an odd function, because then it would comprise only of Sin waves.
And then, out of all the continuous values of w I could take only the one I'm interested in, which is w0, and putting it in B(w) would give me the amplitude of that specific wave.
How is this statement justified? Is B(t) an odd function?