The modalities to validate conceptual advancements in time-domain (TD) electromagnetics (EM) are critically examined. Upon inspecting the capabilities of the existing measurement equipment, it is concluded that expecting a physical verification of frequency-domain (FD) results is fully justified. However, comprehensive direct measurements in the case of TD frameworks do not seem warranted, with TD theories being properly verified only via numerical experiments that offer the needed controlled environment for the relevant proofs.

A time-domain model of the leaky-wave radiation from a slot is assembled via an in-depth numerical investigation. The reported numerical experiments, all making use of a strictly causal excitation, provide a practical guideline for designing leaky-lens antennas (LLAs) and, above all, cogently elucidate the causal mechanism building up the propitious electromagnetic field distribution underpinning the LLA operation.

Pulsed electromagnetic (EM) field signal transfer from a general EM source distribution to a transmission line (TL) is analyzed with the aid of Lorentz's reciprocity theorem. In this fashion, the transient voltage induced by the impulsive EM source is expressed through the EM fields as radiated by the TL. These transmitted EM fields are expressed in closed form using an analytical procedure that resembles the Cagniard-DeHoop (CdH) technique. The validity of the proposed reciprocity-based methodology is verified with the aid of an alternative analytical solution describing the EM field signal transfer excited by an impulsive vertical electric dipole (VED). Illustrative numerical examples are presented.

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.

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.

The late-time evaluation of electromagnetic (EM) field quantities yielded by convolution integrals that combine Green's functions available at discrete time samples and strictly causal excitations is critically revisited. A typical situation is used for tracing the causes of the divergent late-time behavior that is often experienced. A framework combining a suitable integral partitioning with a polynomial approximation is shown to effectively guarantee the integrals' convergence. The formulation is validated via numerical experiments evidencing its accuracy and computational efficacy. The method is amenable to be used in a wide range of problems requiring the late-time evaluation of convolution integrals of the indicated type.

The amplitude-modulated, cosine powerexponential (PE) and windowed-power (WP) pulses are discussed, by insisting on their time-domain normalization. Illustrative examples of signatures and their correspondent frequency-domain behavior are given. These examples compellingly demonstrate the possibility to replace non-causal pulses of prevalent use by causal, or even time-windowed, pulses with closely resembling signatures.

The electric-line-source excited, pulsed electromagnetic (EM) field response on the surface of a highly contrasting thin sheet with dielectric and conductive properties is studied analytically in the time domain (TD) with the aid of the Cagniard-De Hoop technique. Closed-form TD expressions reveal anomalous highly oscillatory EM transients propagated over the surface of the layer. Illustrative numerical examples demonstrate the EM surface phenomenon.

An improvement of the wide-angular scan-loss compensation (SLC) and sidelobe level (SLL) in a small linear array with 23 elements is discussed. The array integrates small subarrays with an optimized pattern for SLC, while the SLL suppression is obtained by using a combination of elements with phase steering only and elements with amplitude/phase control in the center. This combination leads to a less number of T/R module. When the antenna is scanned to ±60°, a maximum first and peak SLL (FSLL and PSLL) of -15.1 dB are obtained. In addition, a -4.6 scan-loss is obtained, it means that the SLC is 2.4 dB with a Cavity-backed U-slotted Patch (CUP) antenna. These performance results are very attractive in particular for a small linear array with wide angular scanning capability.