THE Singularity Expansion Method in Electromagnetics: A Summary Survey and Open Questions

The Singularity Expansion Method (SEM) is probably the most celebrated feather in Carl Baum's cap, among his many other accomplishments such as Nuclear Electromagnetic Pulse (NEMP) simulators, sensors, EM topology etc. SEM was born out of a simple realization that the natural frequencies of both simple (ex: a piece of conducting wire) and complex objects (ex: Boeing 747) are points in the complex frequency or the s-plane. Although expansions based on natural frequencies in mathematical physics preceded Carl's SEM formulation, he must be credited with its vast applicability in the field of NEMP during the cold war era. Coupling coefficients are described as the "transfer function" between the incident waves and the natural modes. The determination of the coupling coefficients was an important step on the path to synthesizing the responses.