# fourier transform basic confused

Discussion in 'Homework Help' started by vead, Dec 29, 2011.

Nov 24, 2011
712
11
hi everyone
i am just begin to learn about Fourier transform
i know Fourier transform is used to analysis of signals such as Rf signal
which convert time domain to frequency domain

for example
f(t)=sin15πt
how to know signal is periodic or aperiodic
how to take Fourier transform of this function

i am trying to learn how time domain is converted in to frequency domain
please someone explain with simple trick

thanks for every help

2. ### Zazoo Member

Jul 27, 2011
114
43
A periodic signal repeats at regular intervals (an aperiodic signal does not.)

For a transform there isn't really a "simple trick" as there is a lot of theory behind the transform itself and how the two domains relate to one another.

There are, however, Fourier transform tables which list transforms for common functions.

3. ### thatoneguy AAC Fanatic!

Feb 19, 2009
6,357
727
Your equation, $sin\omega_0t$ is halfway down the second page of the PDF linked above.

So if there is an FFT for it (though too long for me to type in right now), do you think that means it is periodic or transient/aperiodic? Look at the FFT of your function and decide if there is a constant, or something that will settle to a steady state.