Power spectral density
The random functions

A "deterministic signal" is a function x (t) whose evolution with the time variable t is perfectly predictable and, if necessary, can be expressed analytically. In the case of measurement data, if analytical description is impossible, the function will be presented as a sequence of numerical samples. The developments in this sub-section 4.1 are intended for either presentation.

• Definition and properties of the spectrum of a bounded signal

  The concept of power spectral density uses the properties of Fourier transforms applied to any bounded signalx (t) depending on the time variable t. We'll say that the spectrumX (f) of the bounded signal x (t) results from...