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.

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.

Time-varying (TV) materials have recently gained considerable attention for their ability to manipulate electromagnetic (EM) waves and improve the performance beyond the limits of conventional time-invariant materials. In addition, distributed TV capacitors are becoming more attractive to achieve particular effects. This work presents a systematic approach to modeling TV dielectrics by incorporating TV capacitors in the framework of the partial element equivalent circuit (PEEC) method. Thus, the standard formulation of the PEEC method is modified to include TV dielectrics and lumped elements for general 3D geometries directly in the time domain (TD). It is shown that this is possible through TV capacitances and voltage-controlled current sources. Four numerical examples validate the proposed approach.

The transient electromagnetic (EM) excitation of a narrow slot in a perfectly electrically conducting (PEC) screen that separates two homogeneous dielectric halfspaces, a simplified model of a typical feeding structure of leaky lens antennas, is analyzed numerically in the time domain (TD). The problem is formulated using the TD reciprocity theorem of the time-convolution type and subsequently solved with the aid of the Cagniard-DeHoop method of moments (CdH-MoM). Numerical results are validated using a general-purpose EM-field solver.

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 TD arguments for the effectiveness of this essential element of leaky-lens antennas. The response of the gapped structure to an excitation consisting of pulse trains is evaluated. The discussed results pave the way towards building a genuine TD counterpart of the LWradiation from gap-fed slots. Furthermore, they are conditional to understanding the transients occurring in between intervals when a steady-state, time-harmonic 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.

Analytic time-domain expressions are derived for the pulsed electromagnetic field radiated by a wide slot antenna with a dielectric layer in a two-dimensional model configuration. In any finite time window of observation, exact pulse shapes for the propagated, reflected and refracted wave constituents are constructed with the aid of the modified Cagniard method (the Cagniard-DeHoop method). Numerical results are presented for field pulse shapes at the dielectric/free-space interface, the pulse time widths of the excitation being chosen such that the separate arrivals from the two edges of the slot can be distinguished. Applications are found in any system whose operation is based on pulsed electromagnetic field transfer and where digital signals are detected and interpreted in dependence on their pulse shapes.

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.

Time-domain (TD) methods for the solution of Maxwell's equations are particularly appealing for their ability to provide the overall characteristics of an electrical system in a single simulation run. In many situations, such TD methods require computing the system's impulse response and using it in a convolution-based solver. In this work, we propose the evaluation of the scattering-parameters-type impulse response of partial element equivalent circuit (PEEC) models by firstly computing the scattering parameters pertaining to a unit-step excitation via the Numerical Inversion of Laplace Transform (NILT) technique, followed by recovering the corresponding impulse response. The accuracy and effectiveness of the advocated approach is validated by means of numerical experiments comparing its performance with that of more standard methods.

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.

Thin-wire structures in the presence or absence of a ground plane are analyzed numerically in the time domain (TD) with the aid of the Cagniard–DeHoop method of moments (CdH-MoM). It is demonstrated that the TD solution of such problems can be cast into the form of discrete-time-convolution equations. Under the assumption of piecewise linear space–time axial current distribution, the elements of the TD impedance array are derived analytically in terms of elementary functions. Their approximations applying to multiconductor transmission lines are discussed. Illustrative numerical examples validating the TD solution are presented.

Pulsed electromagnetic (EM) scattering from a relatively narrow superconducting strip is analyzed with the aid of the EM reciprocity theorem and the Cagniard-DeHoop (CdH) technique. The analysis yields a stable convolution-type equation that is solved using the marching-on-in-time (MOT) technique for coefficients representing the time-domain (TD) electric current induced in the strip. Illustrative numerical examples are validated with the help of the CdH method of moments (CdH-MoM).

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.

The critical relevance of ensuring the excitation's causality in electromagnetic (EM) simulations is exploited by the computation of strictly causal time domain interaction integrals as they occur in the partial element equivalent circuit (PEEC) method. Under the hypothesis of thin, almost zero thickness objects, the presented formulas represent analytical impulse responses and, as such, are used within convolutions in the framework of the time domain PEEC solver. The proposed approach is compared with other standard approaches and clearly behaves better than frequency-domain methods in accurately catching the propagation delay and, thus, preserving the causality. Further, improved stability is observed compared to marching-on-in-time methods.

The critical relevance of ensuring the excitation's causality in electromagnetic (EM) simulations is validated via theoretical arguments and simulation results.Two families of model pulses with an implicitly causal behavior, namely the windowed-power (WP) and the power-exponential (PE) ones, are elaborately discussed.After introducing their unipolar prototypes, the relevant families are supplemented with monocycle and ringing variants, and are used for building signatures with almost rectangular spectral contents.Their utility is evidenced by contrasting their performance with that of other types of excitations that are habitually employed in antenna simulations.The WP pulse is also shown to be an almost exact replica of signatures generated by physical circuitry and to be singularly expedient for improving the effectiveness of EM computational packages.

Closed-form time-domain (TD) analytical expressions describing the electromagnetic (EM) signal transfer between two vertical dipoles through a thin, highly contrasting layer with combined magneto-dielectric properties are derived via the Cagniard–DeHoop (CdH) technique with the TD saltus-type conditions. The TD EM-field coupling between the antennas in the absence of the layer is discussed, including its near-field asymptotic solution. It is demonstrated both analytically and numerically that under certain circumstances the combined sheet behaves virtually as a transparent sheet the transition across which inverts the polarity of the received signal.

This article explores some dominant trends in teaching classical electromagnetic (EM) field theory in electrical engineering (EE) undergraduate curricula. The acronym EM will be used interchangeably to designate either electromagnetic or electromagnetism. The intended significance will be evident from the context.