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Ultrasonic fields propagating in viscous media undergo changes in shape due to diffraction, attenuation, and dispersion. Until now, some implementations in the transmission line matrix (TLM) method has been developed to simulate either diffraction or attenuation but never both. In this work, the quadratic frequency dependence of the absorption coefficient as well as the dispersive effect of a viscous fluid are introduced in the TLM method. The idea is to decompose the emitted wave into its components at different frequencies using Fourier transform. Then, dispersion and attenuation effects are considered for each wave component separately before superposing them to get the required acoustic response. This is possible because each one of them is characterized by a constant absorption coefficient and propagates at a single speed. This TLM model has been applied to the diffracted ultrasonic field by a circular transducer radiating a short pulse in a viscous fluid. The obtained waveforms are interpreted in terms of plane and edge waves. A study of the influence of the most important parameters on the waveform of the detected ultrasonic pulses is performed. The numerical results obtained highlight the attenuation effect on the waves' shapes and the influence of the dispersion on their arrival times.

Electronic enclosures often require ventilation and electromagnetic shielding, which have conflicting design requirements. This study proposes a hybrid model, based on circuit model and full-wave method, for estimating the shielding effectiveness of empty metallic enclosures with ventilation apertures of arbitrary shape or aperture arrays of arbitrary distribution on one side of the enclosures. Such perforated enclosures are split into a perforated plate and semi-enclosed waveguide that is shorted at the end. The S parameters of the perforated plate are calculated by a full-wave method and used to estimate the aperture impedance. An equivalent circuit model of a perforated enclosure is established, considering arbitrarily-positioned apertures, arbitrarily-chosen observation points, and higher-order modes. A modified plane wave decomposition technique is adopted to solve the problem of plane waves with arbitrary incident and polarisation directions. In particular, the effects of the electric field components perpendicular to the perforated plate are considered. The efficiency and accuracy of the hybrid model are evaluated by the transmission line matrix method, finite integration technique, experimental observations and existing circuit models. The hybrid model requires much less simulation time than pure full-wave methods such as the transmission line matrix method.

This paper explores the indirect risks of lightning strikes to electric aircraft. We present background on potential impacts, field testing, strike zones, electrical subsystems, and mitigation techniques involved in the analysis of impact of lightning strikes. An explanation of the theory behind the Transmission Line Matrix method is also presented. A commercial tool, CST Studio Suite, was used to model a lightning strike to an aircraft-like structure. Electric field probes are used to analyze the field changes within and outside the aircraft. Additionally, the surface currents on the aircraft are analyzed. Simulations are developed to explore the impact of skin thickness on the level of penetration of electric field on the aircraft subsystems. The results suggests that design based on appropriate parameters for metal skin aircraft can reduce the likelihood of subsystem interference or catastrophic failure of aircraft electrical systems.

Compared ith the traditional wheel-rail train, the maglev train is more vulnerable to lightning strikes due to the lack of contact net protection. In severe cases, it will cause damage to the vehicle-mounted equipment and affect the safety of the train. In order to analyze the indirect effect of lightning on maglev train, the 3D model of maglev train is established. The transmissionline matrix method in CST is used to study the coupling law of cable type, distribution and length of cables under lightning strike. The simulation results show that different types of cables have different coupling characteristics, and the induced current on the shielded cable and the shielded cable is obviously different. With the increase of the distance between the unshielded cable and the bottom of the vehicle and the length of the cable, the induced current of the unshielded cable increases. This method can effectively simulate the indirect effects of the lightning strike on the maglev train, and provides a basis for further research on the protection of the indirect effects of the maglev train.

Proliferation of multi-electric aero-engine industries has resulted in the increase of internal electronic devices. As one of most vulnerable parts of the aircraft, lightning strike would lead to a devastating loss if the engine was caused to malfunction. In view of the above mentioned facts, modeling of geometric and internal cable of turboprop engine were completed, inductive electromagnetic field, surface current on the fuselage and distribution of the induced current in cables were simulated based on transmission line matrix method, meanwhile, the comparison of shielding effectiveness between different skin materials utilized on the fuselage was also investigated. The simulation results show that the internal and external electromagnetic fields at the same axial position of engine are not only different in peak value but also in validation tendency. The location of the cables has a great impact on the internal induced current, which has almost the same value in each cable inside the cable bundle. The shielding effectiveness of nacelle made of carbon fabric composite with bronze mesh is higher than the one without mesh. The research results have a certain guiding significance to clarify the electromagnetic effect of lightning strike to aero-engine, and it is significant for further research activities on the lightning protection.

An analytical model based on the equivalent circuit method is presented to predict the electromagnetic shielding effectiveness (SE) of perforated metallic rectangular enclosure with external waveguide. In this model, the electrically small aperture is represented by a four-terminal network, and the external waveguide and enclosure are modeled as transmission line. By this way, the SE of any position of the enclosure under planewave illumination can be calculated fast and accurately over a wide frequency range (0 ~ 3 GHz). Simulation results of the proposed model are in accord with that of the transmission line matrix method, which verifies the accuracy and reliability of the model. The shielding characteristics of the perforated enclosure with external waveguide are also analyzed. The effects of parameters of aperture position, observation point position, and external waveguide length are discussed in detail. Simulation results show that the external waveguide can effectively improve the SE of the...

In this paper, a hybrid approach of the constrained interpolation profile (CIP) method and the transmission line modeling (TLM) method has been proposed for analyzing lightning electromagnetic fields and surges in the three-dimensional Cartesian coordinate system. The TLM method is employed locally in the working space for representing thin-wire conductors, and the CIP method is used for computing fields in the rest of the working space. Waveforms of lightning electromagnetic fields and surges computed using the CIP-TLM hybrid method agree well with corresponding ones computed using exact analytical expressions or with the finite-difference time-domain method.

A reformulation of the Transmission Line Matrix (TLM) method is presented to model non-dispersive anisotropic media. Two TLM-based solutions to solve this problem can already be found in the literature, each one with an interesting feature. One can be considered a more conceptual approach, close to the TLM fundamentals, which identifies each TLM in Maxwell’s equations with a specific line. But this simplicity is achieved at the expense of an increase in the memory storage requirements of a general situation. The second existing solution is a more powerful and general formulation that avoids this increase in memory storage. However, it is based on signal processing techniques and considerably deviates from the original TLM method, which may complicate its dissemination in the scientific community. The reformulation presented in this work exploits the benefits of both methods. On the one hand, it maintains the direct and conceptual approach of the original TLM, which may help to better understand it, allowing for its future use and improvement by other authors. On the other hand, the proposal includes an optimized treatment of the signals stored at the stub lines in order to limit the requirement of memory storage to only one accumulative term per field component, as in the original TLM versions used for isotropic media. The good behavior of the proposed algorithm when applied to anisotropic media is shown by its application to different situations involving diagonal and off-diagonal tensor properties., Project FIS2017-90102-R of the Ministry of Economy and Competitiveness (MINECO), European Regional Development Fund (FEDER) and the Ministry of Education, Science, and Sport of Spain through the FPU grants for PhD studentship (reference: FPU15/04291)

Purpose The purposes of this paper are to numerically analyse the distribution of the electromagnetic field in the electromagnetic device wherein a high-speed unit exists and to develop a strong tool to analyse the evolution of an electromagnetic field tangled with moving parts. Design/methodology/approach The precise integration time domain (PITD) method and parameter weighted averaging approximation scheme. Findings It is shown that that the electromagnetic field in the device is significantly affected by the velocity of the moving unit and the parameters of the base material. The computation resources of the proposed method are saved and the efficiency is enhanced. Originality/value The parameter approximation (PA)-PITD method can be an effective and efficient time domain method to analyse the evolution of the electromagnetic field in electromagnetic devices with moving parts and similar problems.

In this paper, a refined equivalent circuit model considering semiconductor effect of 3-D ICs is proposed based on three-dimensional transmission line matrix method. In the proposed model, the depletion region around a through silicon via (TSV) is modeled as distributed voltage-dependent capacitors and resistors. With the proposed model, noise behaviors could be accurately obtained under relatively short simulation time when compared to the time needed by full wave simulators. The simulation result of the proposed model is aligned with both ANSYS HFSS and TCAD Sentaurus in frequency and time domains while the simulation time is greatly reduced to less than 1%. The influence of TSV-induced substrate noise on an active circuit is demonstrated using the proposed model. The CMOS inverter affected by the noisy substrate shows up to 34-mV deviation at the inverter output when compared to the inverter on a noise-free substrate.

The Gauss-Seidel preconditioned conjugate gradient method applying to element-by-element finite-element method (EBE-FEM) is derived and the calculation process is presented in this paper. The EBE-FEM is a parallel numerical algorithm, in which a conjugate gradient (CG) type iterative solution scheme can be entirely decomposed into computations on the element level without assembling the global system matrix. The validity and accuracy of the proposed method have been verified through the applications to magnetic field analysis of a long straight current-carrying wire and a three-phase electric motor. Compared with the Jacobi preconditioned CG method applying to EBE-FEM, less computational time and cost are needed for the proposed method with the same accuracy. The proposed method can be applied to electromagnetic field analysis of power transformer and electric motor, which may be related to large-scale numerical computation.

In this paper, we present a new time-domain method that has a naturally diagonal mass matrix and thereby a strict linear computational complexity per time step, regardless of whether the discretization is a structured grid or an unstructured mesh. This property is obtained independent of the element shape used for discretization. No interpolations, projections, and mass lumping are required. The accuracy and stability of the proposed method are both theoretically guaranteed. In addition, no dual mesh is needed and the tangential continuity of the fields is satisfied across the element interface. The flexible framework of the proposed method also allows for a straightforward extension to higher order accuracy in both electric and magnetic fields. Numerical experiments have been conducted on a variety of unstructured triangular-element meshes. Correlations with analytical solutions and the time-domain finite-element method have validated the accuracy and generality of the proposed new time-domain method.

This paper presents the interconnected multi-1-D (IM1-D) fundamental alternating-direction-implicit finite-difference time-domain (FADI-FDTD) and fundamental locally 1-D finite-difference time-domain (FLOD-FDTD) methods for transmission lines with interjunctions. The proposed methods are unconditionally stable and capable of treating multiple main transmission lines and stubs interconnected at various interjunctions using time step larger than Courant–Friedrichs–Lewy limit. Fundamental scheme-based IM1-D FADI- and FLOD-FDTD methods are derived to enhance the efficiency with matrix-operator-free right-hand sides. The methods involve one-step update procedure optimized for simulation of main transmission lines and stubs on mobile device. Using proper treatments at the interjunctions for various interconnection conditions, the electromagnetic fields in all interconnected main transmission lines and stubs can be updated cooperatively and efficiently to solve practical problems. A microstrip line loaded with stubs and a branch-line coupler are simulated to show the accuracy and efficiency of the proposed methods. To extend the applicability for handling the couplings between two transmission lines via gaps, a microstrip circuit with gaps is simulated using the proposed methods incorporated with equivalent circuit models involving capacitances. Real-time simulations of these numerical examples provide much intuitional insight for one to observe the electromagnetic waves propagation in time domain on computer or mobile device.

The $N$ -port equivalent Thevenin representation of a power-ground structure is constructed using the Lorentz reciprocity theorem of the time-convolution type. It is shown that the introduced multiport Kirchhoff-circuit representation offers a number of alternative routes to determining the pulsed electromagnetic radiated emissions of a power-ground structure from its response to an electromagnetic disturbance in the receiving situation. Moreover, the result may serve as an important check on the validity of numerical solutions to related electromagnetic radiation problems. An illustrative example that validates the equivalent-circuit representation is given.

A hybrid spectral-element finite-difference time-domain (FDTD) method is proposed for electromagnetic simulation in this letter. This proposed hybrid method takes full advantage of the efficiency of FDTD method with the traditional Yee's grid and the flexibility of spectral-element time-domain method in modeling complex geometry, and it inherits the powerful ability in parallelism. Furthermore, the discontinuous Galerkin method is employed to improve the efficiency in dealing with nonconforming meshes. Numerical results demonstrate the accuracy and robustness of the proposed method.

This paper presents an algorithm for estimating the variance in simulated electromagnetic fields arising from uncertainties in electrical parameters in a model. The proposed algorithm is shown to be faster and more accurate than the stochastic finite difference time domain method. The main advantage of the algorithm lies in how does not slow down the main simulation of electromagnetic fields, since it is only performed on demand after the main simulation is completed.

This work evaluates the applicability of computational electromagnetic methods for the determination of Cavity Calibration Factors for aircraft weapon bays. Cavity Calibration Factors provide a prediction of maximum expected electrical field levels in a weapon bay for evaluating EMC, including hazards of electromagnetic radiation to ordnance. A generalized geometry is created with traits similar to an aircraft bay. The Transmission Line Matrix method is used to simulate the response of the bay across two frequency bands; 800–2500 MHz using a near field source and 5300–5900 MHz using a tuned dipole. Results are evaluated for chi-squared distribution with six degrees of freedom and the total number of modes contained at four frequencies; 915, 1830, 2250, and 5600 MHz.

The possibility of terahertz imaging in medical applications is investigated by the design and implementation of an electromagnetic system. Numerical analysis based on the transmission line matrix method is used to obtain the shape or form of the biological object. The effect of different discretization parameters on the convergence of the transmission line matrix method is studied in detail. Exact and efficient dielectric profile image reconstructions of three dimension lossy scatterers from different complex cross sections using synthetic scattered field data are presented. The influence of antenna spacing and the suitability of the simplified transmission line matrix model for system evaluation are examined.

Photovoltaic PV module must be able to endure the effects of periodic hot-spots heating that can occur when panel cells are operated under reverse biased conditions. For practical applications, it is important to accurately estimate the junction temperature of PV cells and analyze their thermal characteristics. However, panel manufacturers generally do not provide information about the behavior of their cells under the shadowing conditions. To deal with this issue, analytical and simulation studies can provide the needed feedback to anticipate any internal cell failure process. In this paper, the analytical model based on the solutions of the governing heat equations is used in order to determine temperature fields of a solar panel in reverse bias mode to select and predict expected and risked hot spots. It was observed that each unit shaded cell is capable to self-generating an amount of heat, which needs to be removed efficiently to anticipate any failures process. To compare results the Transmission Line Matrix method (TLM) and finite element method (FEM) using the Msc Patran/Nastran software are used to map the surface temperature distribution. A good consistency has been observed by accepting an error less than 2% for TLM model and error less than 4% for FEM model. The analytical method helps to select and locate the expected hot spots in shadowed panel and to highlight the need of thermal study pre-design thus to minimize the system-level thermal dissipation and then lead to higher reliability.

In this paper, we propose a simulation model of electromagnetic wave's propagation in dispersive media using Transmission Line Matrix method with the symmetrical condensed node (SCN - TLM) and novel voltage sources. The proposed model, named GVADE- TLM, allows the simulation of optical pulses propagation in nonlinear optical medium, by solving Maxwell's equation and the polarization current density. The model is applied to problems where the electric field is not constrained to a single vector component. The scattering matrix characterizing the SCN with the new voltage sources is provided and the numerical results are compared with those of the literature or with the theoretical ones.

This paper presents a novel time domain hybrid method consisting of finite-difference time domain (FDTD) method, transmission line (TL) equations, and circuit-based method, which can be directly applied in time domain for the electromagnetic interference (EMI) analysis of the lumped circuits in a shielded device excited by ambient electromagnetic wave. The FDTD method coupled with the TL equations is utilized to model the electromagnetic properties of arbitrary structures containing transmission lines and shielded enclosure of the electronic device with any ambient excitation. With numerical simulation, an equivalent circuit model considering the external EMI effects is extracted as an excitation source for the internal lumped circuit according to Thevenin's theorem. Then, the state variable approach is used for the further EMI analysis of the internal lumped circuit in time domain. Two cases, in which a transmission line and/or a transmission line network are connected to a lumped circuit within a shielded enclosure excited by an intense electromagnetic pulse, are computed with the proposed method. The numerical results are compared with those obtained by using the FDTD method, and they are almost in perfect agreements. Meanwhile, at last, an example of this method applied for the EMI protection of an electronic device is given.

We develop a new matrix-free time-domain method, which requires no matrix solution, in unstructured meshes for general 3-D electromagnetic analysis. The method handles arbitrary unstructured meshes with the same ease as a finite-element method. Meanwhile, it is free of matrix solutions manifested by a naturally diagonal mass matrix, just like a finite-difference time-domain method. Different from our previous formulation where traditional curl-conforming vector bases are employed, modified vector bases are developed in this paper to directly connect the unknown coefficients of the vector basis functions employed to represent E (or H) with the unknowns obtained from the curl of H (or E), without any need for transformation. The proposed method employs only a single mesh. It does not require any interpolation and projection to obtain one field unknown from the other. Its accuracy and stability are guaranteed theoretically. Numerous experiments on unstructured triangular prism and tetrahedral meshes, involving both homogeneous and inhomogeneous and lossy materials, demonstrate the generality, accuracy, stability, and computational efficiency of the proposed method. The modified higher order vector bases developed in this paper can also be used in any other method that employs higher order bases to obtain an explicit relationship between unknown fields and unknown coefficients of vector bases.

This paper presents an improved circuit model for the prediction of the shielding effectiveness and resonances of an enclosure with apertures. In the model, an aperture position factor is introduced to deal with an off-centered aperture. The factor considers the effect of higher order modes, and is thus more accurate than those considering the effect of TE10 mode only or considering the effect of higher order modes incorrectly. Moreover, because of the factor, multiple apertures are not required to be similar and can have arbitrary distribution. Three orthogonal components of voltage response are considered based on the waveguide theory; therefore, higher order modes including ${\rm TM}_{\rm mn0}$ modes can be predicted precisely, which are not possible with those previous circuit models derived from Robinson's model. Besides, monitor point can locate anywhere within enclosure and aperture can have arbitrary length–width ratio. The presented model provides a more accurate means for the prediction of the shielding effectiveness and higher order modes of an enclosure with arbitrarily positioned apertures over a wide frequency range compared with other existing circuit models, and costs much less solution time and fewer computing resources than traditional numerical methods. The validity of the presented model is verified by the transmission line matrix method.

We have investigated a high-accuracy analysis for the electromagnetic field of numerical human body models using the finite-element method. The numerical human body models generated from computed tomography images are represented as voxel data, and composed of skin layers, blood vessels, bones, internal organs, and so on. In this paper, we propose a mesh smoothing technique to reduce the noise caused by reflection and scattering of the electric fields around material boundaries. Therefore, using a supercomputer, we successfully evaluated the electromagnetic field distribution inside the whole body model with a high accuracy.

In order to improve the computation efficiency for analyzing the underwater electromagnetic propagation at low frequency, a novel parallel total-field scattered-field source finite-difference time-domain (FDTD) method is presented in this letter. The accuracy and validity were verified by comparison to the analytical solution. Numerical results show that the parallel speedup of 13.68 and efficiency of 68.4% are obtained with 20 processors.

Inelastic deformation of conductive bodies under the action of electromagnetic fields is analyzed. Governing equations for non-stationary electromagnetic field propagation and elastic–plastic deformation are presented. The variational principle of minimum of the total energy is applied to formulate the numerical solution procedure by the finite element method. With the proposed method, distributions of vector characteristics of the electromagnetic field and tensor characteristics of the deformation process are illustrated for the inductor–workpiece system within a realistic electromagnetic forming process.

Analysis of the interaction between high-power electromagnetic (HPEM) pulse and targets is often carried out in free space. However, the half-space effect cannot be ignored when targets are located near the ground. Electromagnetic field and energy-flux density coupling into a radome over lossy half-space are investigated based on a semianalytic method. In this paper, the interaction of the EM wave and the radome is computed by finite-difference time-domain (FDTD) method. The bidirectional incident wave of the FDTD region is introduced by the Fresnel formula, Fourier transform, and the equivalence principle. Finally, different incident conditions such as incident planes and polarization modes are discussed. The numerical results show that this method can provide a reliable technique for estimating the electromagnetic coupling effects on targets over half-space under HPEM pulses.

TLM Summary • Highly versatile full-wave 3D time-domain method • Uses scattering and connecting of voltage pulses in a mesh of transmission-lines to simulate EM fields • Conformal meshing improves accuracy, cell-lumping improves efficiency • Compact models may be used to capture important detail such as thin panels, apertures and wires • Wide range of applications including shielding, radiated emissions and susceptibility

A three-dimensional thermal simulation investigation for the thermal management of GaN-on-SiC monolithic microwave integrated circuits (MMICs) of consisting multi-fingers (HEMTs) is presented. The purpose of this work is to demonstrate the utility and efficiency of the three-dimensional Transmission Line Matrix method (3D-TLM) in a thermal analysis of high power AlGaN/GaN heterostructures single gate and multi-fingers HEMT SSPA (solid state power amplifiers). The self-heating effects induce thermal cross-talk between individual fingers in multi-finger AlGaN/GaN that affect device performance and reliability. Gate-finger temperature differences only arise after a transient state, due to the beginning of thermal crosstalk which is attributed to the finite rate of heat diffusion between gate fingers. The TLM method accounts for the real geometrical structure and the non-linear thermal conductivities of GaN and SiC in order to improve the realistic calculations accuracy heat dissipation and thermal behavior of the device. In addition, two types of heat sources located on the top of GaN layer are considered in thermal simulations: Nano-scale hotspot as a pulsed wave heat source under gate and micro-scale hotspot as a continuous wave heat source, between gate and drain. Heat diffusion however, occurs not only between individual gate fingers (inter-finger) in a multi-finger HEMT, but also within each gate finger (intra-finger). To compare results, a Micro-Raman Spectroscopy experience is conducted to obtain a detailed and accurate temperature distribution. Good agreement between the microscopic spectral measurement and TLM simulation results is observed by accepting an error less than 2.2% relative to a maximum temperature. Results show that the 3D-TLM method is suitable for understanding heat management in particular for microwave devices AlGaN/GaN HEMTs SSPA amplifier. TLM method helps to select and locates the expected hot spots and to highlight the need of thermal study pre-design in order to minimize the system-level thermal dissipation and lead therefore to higher reliability.

In this paper, an electromagnetic simulation methodology and workflow for high voltage multi-level converter stations is presented, which is based on the transmission line matrix method as used in CST Studio Suite. The methodology makes use of the thin wire models of CST, which are well suited to represent the high voltage bus bars and cables connecting the 3-dimensional structures of the converter valves and halls. Additional key components such as grid transformers and phase reactors are included as hybrid models, consisting of 3-dimensional structures in combination with imported circuit netlists. The converter itself is modeled as impulse sources in the CST circuit schematic, where the switching pulse patterns and the cell switching characteristics are taken into account in a final post-processing step in combination with electromagnetic interference (EMI) detector models. The obtained accuracy in the target frequency range from 10 kHz to 10 MHz, is about ±5 dB, when compared to actual electromagnetic (EM) field measurements.

Accurate electrical models for Through Silicon Via (TSV) are critical for 3D integration system design, in which TSV capacitance plays an important role. Minority carrier redistribution (MCR) effect, the spatial position rearrangement of minority carrier in inversion layer, is considered in TSV modeling in this paper. The importance of taking MCR into account is illustrated by comparing the TSV capacitance calculated by capacitance models with and without MCR for a square-shape TSV. Parametric study of errors result from neglecting MCR is performed on several physical and material parameters. A more accurate electrical model for square-shape TSV based on 3D transmission line matrix method (3D-TLM) is proposed, and transient analysis using this model is performed to reveal the effect of MCR on the noise coupling.

A novel three-dimensional (3D) lumped circuit-based metamaterial topology to model a 2D fishnet structure is proposed. The rotated transmission-line matrix (RTLM) unit cell, obtained as one independent half cell from the typical TLM unit cell by rotating the polarisations on each TLM unit port by 45°, saves computation time and decreases the cost in processing data when a structure is analysed, especially when some specific components of the structure are processed. Here, an RTLM unit cell is used to construct the lumped circuit of a fishnet structure. The dispersion characteristics of the lumped fishnet circuit are obtained and used to analyse the eigenmode and the propagation coefficient and Bloch impedance are investigated to explain the frequency characteristics. At the frequency region considered, the same left-handed frequency behaviour of the lumped fishnet circuit is achieved by the proposed compact fishnet RTLM model, agreeing well with the simulation results.

The transmission-line matrix method enhanced with the compact wire model in a cylindrical grid is used for modelling of a coaxially loaded cylindrical cavity resonator with probes inserted into the cavity. Benefits of using a cylindrical grid instead of rectangular, related to precise modelling of cavity boundaries, a coaxially shaped dielectric sample and radially placed wire elements, are explored. The accuracy of the simulated results is verified by measurements of an experimental model of the cavity-wire structure.

Microwave component design by electromagnetic structure synthesis is attractive because the electromagnetic field has the inherent property to minimize loss, sensitivity to tolerances, and vulnerability to field breakdown. However, it is conceptually and computationally challenging, and its technical possibilities have thus been explored only tentatively so far. This paper introduces a first, but critical new step towards systematic electromagnetic structure synthesis, based on computational time reversal, and employing the time and space discrete transmission line matrix (TLM) method. The novelty of this paper resides in the exploitation of the scattering nature of the TLM model, which allows the near-field of a source or a scatterer to propagate into the far-field and back. By ignoring the conventional restriction that spatial wavelengths must always be much larger than the space discretization step, one can reconstruct multiple impulsive sources with the spatial and temporal resolution of the TLM algorithm. This crucial insight promises to be the key to a successful synthesis strategy. This paper describes the reconstruction of electromagnetic sources through computational time reversal, demonstrates the self-consistency of this procedure by means of a validation example, and outlines the next steps towards a full electromagnetic synthesis capability.

A time domain hybrid method is presented for efficiently solving the electromagnetic coupling problems of transmission lines in cavity. The proposed method is based on the finite-difference time-domain (FDTD) method and transmission line (TL) equations (FDTD-TL), which can achieve a strong synergism on the computations of field and circuit. The FDTD method with an auto mesh generation technique is employed to obtain the electric fields of transmission lines excited by an incident wave from the outside of the cavity. The electric fields are introduced into the TL equations as additional voltage sources at each time step of FDTD method. The current and voltage responses of terminal loads can be obtained by the TL equations. Two examples are presented to demonstrate the correctness of this method. The high efficiency of this hybrid method is verified by comparing the computation time with the traditional method.

In this paper, an efficient method for the numerical simulation of near- and far-field propagation of stochastic electromagnetic (EM) fields is presented. The method is based on the transformation of field correlation dyadics using Green's functions or the field transfer functions computed for deterministic fields. The method accounts for arbitrary correlations between the noise radiation sources and allows to compute the spatial distribution of the spectral energy density of noisy electromagnetic sources. The introduced methodology can be combined with available electromagnetic modeling tools. It is shown that the method of moments can be applied to solve noisy electromagnetic field problems by network methods applying correlation matrix techniques. Examples demonstrating the strong influence of the correlation between the sources on the spatial distribution of the radiated noise field are presented.

In this paper, a procedure for computing transient electromagnetic fields with the constrained interpolation profile (CIP) method in the two-dimensional (2-D) cylindrical coordinate system has been derived. Then, it has been applied to analyzing electromagnetic pulses produced by a current wave propagating upward along a vertical lightning return-stroke channel. CIP-computed waveforms agree well with corresponding waveforms computed using analytical expression of Uman et al. or the finite-difference time-domain method.

The effectiveness of the random coupling model (RCM) in predicting electromagnetic wave coupling to targeted electronic components within a complex enclosure is examined. In the short-wavelength limit with respect to the characteristic length of the enclosure, electromagnetic wave propagation within a large enclosure is sensitive to small changes to the interior, or to the boundaries of the enclosure. Such changes can reduce or invalidate the applicability of deterministic predictions of the electromagnetic fields at radiofrequencies (RF) in large enclosures. Under such circumstances, a statistical approach is needed to provide a better understanding of RF coupling to components within large enclosures. In this paper, we experimentally demonstrate the applicability of a statistical technique, the RCM, to estimate the probabilistic magnitudes of RF fields on electrically large components (i.e., long cables, etc.) that are partially shielded within a complex, 3-D enclosure.

The electromagnetic field propagated between two perfectly electrically conducting screens is investigated in the time domain using two approaches. In addition to a solution based on the well-known eigenfunction expansion, we provide an alternative series expansion composed of generalized-ray constituents. As the constructed closed-form space-time expressions are straightforward and easy to implement in any computational tool, they may serve for educational purposes. In particular, they may be useful for those who want to get acquainted with some basic aspects of the propagation of the pulsed electromagnetic field. Key features of both time-domain approaches are discussed, and illustrative numerical examples are given.

This paper deals with TLM modelling issues mostly pertaining to create the model, mesh adjustments, and simulation efficiency on an example of a cylindrical-rectangular coax-fed microstrip patch antenna. Possibilities, advantages, and limitations of the TLM solvers based on cylindrical and rectangular coordinate systems are investigated through simulations and discussed in detail.

We extend the classical results on the symmetry inheritance of the canonical electromagnetic fields, described by the Maxwell's Lagrangian, to a much wider class of models, which include those of the Born-Infeld, power Maxwell and the Euler-Heisenberg type. Symmetry inheriting fields allow the introduction of electromagnetic scalar potentials and these are proven to be constant on the Killing horizons. Finally, using the relations obtained along the analysis, we generalize and simplify the recent proof for the symmetry inheritance of the 3-dimensional case, as well as give the first constraint for the higher dimensional electromagnetic fields., Comment: 6 pages; slightly revised, published version (two statements removed from the Theorem II.1, equations (25) and (26) corrected, several comments added/revised)

Finite-element method (FEM) has been widely used in industrial applications for many years. With the increase of finite-element model complexity and the number of elements, computation burden has become a serious issue and requires more attention. In this paper, the transmission line method (TLM) is adopted to the solution of FEM-based nonlinear axisymmetric magnetostatic problem and an equivalent finite-element network’s circuit model is given. Several methods were investigated to speed up the computation, such as Newton preconditioners, simplification of nonlinear equation solution and parallel computation. Compared with traditional Newton FEM iteration, our results show that the proposed method has more obvious advantages on computational efficiency at the same calculation accuracy. The method is applicable and valuable in the characteristic analysis and design of the magnetic device with a cylindrical structure.