Re: I need help with this simple fourier transform

On Oct 23, 10:05 pm, NZTideMan <mul...@xxxxxxxxx> wrote:
On Oct 23, 9:38 pm, "diego sened" <diego9...@xxxxxxxxx> wrote:

Sorry, i'm a n00b Rolling Eyes

Consider this analog signal xa(t) = sin(20*pi*t + pi/4) with t included between [0,1].
If we sample it with Tsample= 0.05, we will have x(n).
Now calculate fourier transform both for xa(t) and x(n).

For xa(t) i tried:
t=[0:0.001:1];
xa =sin(20*pi*t + pi/4);
then Xa= fft(xa);
f=t;
but doing plot(f,abs(Xa)) i see only two dirac delta on 0 and 1.... and it's not right. Please help me!

Hey Diego
Why didn't you continue with the posting you started earlier?
Two dirac deltas is exactly what I'd expect, one at +0.05Hz and the
other at -0.05Hz.
Your problem is that you've calculated f wrongly.
You need to go back to your lecture notes on the calculation of
frequency.

Oops, I mean + and - 20 Hz, 0.05 s period.
.

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