Non-consistent normalization problem in fft

1. What is normalization in FFT?
2. What are the disadvantages of FFT?
3. Why Fourier transform is not suitable for non stationary signals?

What is normalization in FFT?

Normalise the fft by dividing it by the length of the original signal in the time domain. Zero values within the signal are considered to be part of the signal, so 'non-zero samples' is inappropriate. The length to use to normalise the signal is the length before adding zero-padding. Mustafa Rifat on 1 Nov 2021.

What are the disadvantages of FFT?

A disadvantage associated with the FFT is the restricted range of waveform data that can be transformed and the need to apply a window weighting function (to be defined) to the waveform to compensate for spectral leakage (also to be defined). An alternative to the FFT is the discrete Fourier transform (DFT).

Why Fourier transform is not suitable for non stationary signals?

Such a signal shows no variation in time and hence contains only a component with frequency 0 (this is a DC signal). This means that its Fourier transform must be 0 everywhere, except in f=0. Mathematically, X(f)=δ(f).