A strictly causal numerical study of the pulsed operation of a weakly dispersive, leaky wave (LW) antenna is presented. The intricacies at the forefront of the electromagnetic (EM) field radiated from a gap-fed slot in a perfectly electrically conducting (PEC) sheet are evidenced for the first time. The radical effect of a free-space gap separating the PEC sheet from the dielectric half-space into which the slot radiates is demonstrated, thus providing time-domain (TD) arguments for the effectiveness of this essential element of leaky-lens antennas (LLAs). The response of the gapped structure to an excitation consisting of pulse trains is evaluated. The discussed results pave the way toward building a genuine TD counterpart of the LW radiation from gap-fed slots. Furthermore, they are conditional to understanding the transients occurring in between intervals when a steady-state, time-harmonic (TH) operation can be assumed, an extremely relevant ingredient to implementing highly complex modulations in carrier-based, wireless transfer.

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The pulsed electromagnetic (EM) field radiated by a gap-fed, long slot in a perfectly conducting thin sheet located in between dielectric and free-space subdomains is examined. A phenomenological interpretation of the so-called head wave (HW) constituent is proposed, this fostering the understanding of the complex EM behaviour at, and immediately behind, the HW wave-front. The EM field is also examined numerically for identifying features that may lead the way towards inferring a causal counterpart of the leaky-wave propagation.@en

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.

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A simple and efficacious modality of introducing causal excitations in CST Studio Suite® time-domain simulations is described. It makes use of (concatenations of) so-called discrete ports that are shown to accurately substitute Dirichlet boundary conditions and replicate dipole excitations. Numerical experiments cogently demonstrate the approach's exceptional replication accuracy and computational effectiveness.@en