At which frequencies is located the detail information of the signal after FFT?

[zonetone]

Hi everybody!
I'm wondering at which frequencies is located the information that describes the details of the signal after FFT?
I know that it is located at the high frequencies of the frequency domain, but I'm wondering is there a way to calculate exactly which are the frequency components that contain that information?
Thank you in advance!

 

[lebesgue]

Your question is not clear. What do you mean by this? " at which frequencies is located the information that describes the details of the signal after FFT"

 

[zonetone]

If we look at DFT formula:
N-1
S[kΩ]=Σ S[nT].e^(-j2πkn/N), 0 ≦ k ≦ N-1
n=0

If I'm not mistaking, after we calculate the frequency spectrum,i.e. S[kΩ], the small numbers k, are the low frequency components(harmonics with small numbers), which contain the main part of the spectrum of the signal. And the harmonics with big numbers,i.e. big values of k, contain the detail information of the signal such as fronts.
I'm wondering how to determine exactly which frequency components contain the detail information for the signal, after we do FFT on the original signal, i.e. I need a way to understand which are the numbers k of those components, so I can take their values and work with them?


I hope I have explained it right, because I don't have much experience in signal processing. :smile: