The Volterra series is a model for non-linear behavior similar to the Taylor series. It differs from the Taylor series in its ability to capture "memory" effects. ... In mathematics, a Volterra series denotes a functional expansion of a dynamic, nonlinear, time-invariant functional. Volterra series are frequently used in system identification ...

A Fourier series (/ ˈ f ʊr i eɪ,-i ər /) is a sum that represents a periodic function as a sum of sine and cosine waves. The frequency of each wave in the sum, or harmonic, is an integer multiple of the periodic function's fundamental frequency.Each harmonic's phase and amplitude can be determined using harmonic analysis.A Fourier series may potentially contain an infinite …