Second-Order Representation of Signals

During the past decades much effort has been devoted to the adequate representation of signals in various fields such as acoustics and (bio-)electrical engineering. Among others, this resulted in a number of second order signal representations, each one with its own particular characteristics and special domain of application. A number of these functionals can be met regularly in the literature dealing with the problems of localization and identification of signal sources, both in technical and biological applications. Especially those second order functionals which have time and/or frequency, in the various possible configurations, as arguments have shown to be of particular interest: e.g. the lagged product function, the ambiguity function (Woodward 1953, Rihaczek 1969), the bispectrum, the Wigner-distribution (Wigner 1932, Claasen and Mecklenbrauker 1980), and the Rihaczek-CoSTID (Johannesma and Aertsen 1983). In the present paper we present a general scheme providing the formal relations between these functionals.