Introduction - If you have any usage issues, please Google them yourself
Spectral analysis of the signal is to calculate the signal spectrum (Fourier transform of the signal), through the signal analysis of signal characteristics. Signal spectrum is continuous, can not be used to calculate the digital signal processing method, according to the frequency domain using the theorem, the sequence of DFT fully reflects the spectral information, so you can spectrum analysis by DFT.
The FFT and the time domain discrete signal are analyzed by FFT.