ON CIRCULARITY

Circularity is an assumption that was originally introduced for the de finition of the probability distribution function of complex normal ve ctors. However, this concept can be extended in various ways for nonno rmal vectors. The first purpose of this paper is to introduce and comp are some possible definitions of circularity. From these definitions, it is also possible to introduce the concept of circular signals and t o study whether or not the spectral representation of stationary signa ls introduces circular components. Therefore, the relationships betwee n circularity and stationarity are analyzed in detail. Finally, the th eory of linear mean square estimation for complex signals exhibits som e connections with circularity, and it is shown that without this assu mption, the estimation theory must be reformulated.