Time-Domain Electromagnetic Leaky Waves

A causality preserving interpretation of the electromagnetic (EM) leaky-wave (LW) propagation in space and time is proposed for the first time. The Cagniard–deHoop (CdH) joint transform technique is applied for elucidating the relation between time-domain (TD) head waves (HWs), body waves (BWs), Cherenkov wave effects, and LWs. It is conjectured that the LW phenomenon in the TD is associated with a local maximum in the observed signal that occurs between the arrivals of the HW and BW constituents. A quantitative analysis that enables the space-time localization of the LW effect is performed theoretically and, then, illustrated via representative examples including the pulsed EM radiation from both a line source above a dielectric half-space, and narrow-slot antennas.

I. Introduction

Leaky waves (LWs) can be viewed as nonmodal solutions (or noneigenmodes) of the source-free field equations in an open space. Owing to their improper physical behavior, LWs cannot exist on their own, but they can be utilized to represent the total field in a bounded subdomain of space [1]. Such solutions were dominantly investigated under the assumption of sinusoidally in time-varying fields, i.e., in the frequency domain (FD) (see [1], [2], [3], [4], [5], [6], [7], [8], [9], [10, Sec. 11.8]).