Asymptotic Techniques for Transient Analysis

Abstract

This chapter presents high-frequency solutions pertinent to the problems of transient scattering and radiation from electrically large, perfectly conducting bodies. In particular, the aympotic techniques, including time domain uniform geometrical theory of diffraction (TD-UTD) and time domain physical optics (TD-PO), for solving the scattering and radiation problems are described. Regardng the TD-UTD, the analysis of transient scattering from short-pulse excited perfectly conducting curved surfaces along with the analysis of transient radiation and surface fields of elemental pulsed antennas placed directly on a smooth perfectly conducting, arbitrary convex surface is described. As for the TD-PO, an analytical and closed-form solution pertinent to the fast analysis of transient scattering from a finite and perfectly conducting ellipsoidal surface illuminated by a transient-step plane wave is presented. The presented techniques are able to be adopted for finding high-frequency solutions pertinent to the transient problems, such as scattering from aircrafts and spacecrafts under short-pulse excitation, radiation from the antennas of short pulse radars, as well as mutual coupling in complex electromagnetic radiating systems. On the other hand, more physical insight crucial to an in-depth understaning of the transient wave phenomena can be gained with the ray solutions from the TD asympyotic techniques.