V.A. Bazhenov, O.S. Pogorelova and T.G. Postnikova
state-of-art technique for nonstationary signals analysis. There are quite a few articles, books, and textbooks written on them [ 11 , 12 , 13 , 14 ]. There is developed Software: Wavelet Toolbox in Matlab, Mathcad and so on [ 15 ].
Mathematical transformations are applied to signals to obtain a further information from signal that is not readily available in the raw signal. There is number of transformations that can be applied, among which the Fourier transforms (FT) are probably by far the most popular.
The FT gives the frequency information of the signal