I am facing an interesting problem: I have a signal in the time domain. In order to avoid discontinuities at the edges of the signal --- which would lead to artifacts when calculating the FFT --- I apply a window function, like e.g. hann or hamming. Then I perform the FFT of this windowed signal.
To preserve the energy of the signal after the FFT, I calibrate the FFT of the windowed signal with the RMS of the window function. However, the strange thing is that the energy (=area under the curve) of the windowed signal in the frequency domain is substantially different (about a factor of 2) compared to the FFT of the unwindowed signal.
Do you have an idea where this issue could originate from?
Thanks a lot in advance!