Why so many methods of computing PSD?

1. Which method is used to find PSD?
2. Why use Welch PSD?
3. What are the difficulties in FFT based power spectral estimation methods?
4. How is PSD calculated in FFT?

Which method is used to find PSD?

The PSD is estimated by averaging these individual DFTs of overlapping segments. A wider EEG window may lead toward better frequency resolution. Another technique utilizing auto regressive (AR) modeling may also be implemented to estimate the PSD.

Why use Welch PSD?

Welch's method is an improvement on the standard periodogram spectrum estimating method and on Bartlett's method, in that it reduces noise in the estimated power spectra in exchange for reducing the frequency resolution.

What are the difficulties in FFT based power spectral estimation methods?

The common problem of the two methods is that the variance of the estimation is not good, and the estimated value along the frequency axis of the fluctuation is more severe; the longer the data, the more serious the phenomenon.

How is PSD calculated in FFT?

A PSD is computed by multiplying each frequency bin in an FFT by its complex conjugate which results in the real only spectrum of amplitude in g².