Showing papers on "Computational electromagnetics published in 2022"

Parallel Higher Order DGTD and FETD for Transient Electromagnetic-Circuital-Thermal Co-Simulation

Abstract: A hybrid higher order discontinuous Galerkin time-domain (DGTD) method and finite-element time-domain (FETD) method with parallel technique is proposed for electromagnetic (EM)–circuital–thermal co-simulation in this article. For electromagnetic simulation, DGTD method with higher order hierarchical vector basis functions is used to solve Maxwell equation. Circuit simulation is carried out by modified nodal analysis method. For thermal simulation, FETD method with higher order interpolation scalar basis functions is adopted to solve heat conduction equation. To implement electromagnetic–circuital–thermal co-simulation, the electromagnetic and circuital equations are strongly coupled through voltages, currents, and electric fields at the lumped ports first. Then the electromagnetic and thermal equations are weakly coupled with electromagnetic loss and temperature-dependent medium parameters. Finally, large-scale parallel technique is used to accelerate the process of multiphysics simulation. Numerical results are given to validate the correctness and capability of the proposed electromagnetic–circuital–thermal co-simulation method.

Topology Optimization for Electromagnetics: A Survey

Abstract: The development of technologies for the additive manufacturing, in particular of metallic materials, is offering the possibility of producing parts with complex geometries. This opens up to the possibility of using topological optimization methods for the design of electromagnetic devices. Hence, a wide variety of approaches, originally developed for solid mechanics, have recently become attractive also in the field of electromagnetics. The general distinction between gradient-based and gradient-free methods drives the structure of the paper, with the latter becoming particularly attractive in the last years due to the concepts of artificial neural networks. The aim of this paper is twofold. On one hand, the paper aims at summarizing and describing the state-of-art on topology optimization techniques while on the other it aims at showing how the latter methodologies developed in non-electromagnetic framework (e.g., solid mechanics field) can be applied for the optimization of electromagnetic devices. Discussions and comparisons are both supported by theoretical aspects and numerical results.

A Unified View of Computational Electromagnetics

Abstract: This article presents a unified description of numerical methods for solving electromagnetic field problems. Traditionally, these methods are considered to be independent and alternative ways of solving Maxwell’s equations or equations derived therefrom. However, they all are projective approximations of the unknown solution by known expansion or basis functions with unknown amplitude coefficients that are determined using the so- called method of weighted residuals (MWR). This common feature forms the proposed unifying framework that may serve both as a systematic introduction to computational electromagnetics and as a way to provide insight into the nature, strengths, and limitations of the various algorithms used by present and future field solvers. For convenience, the fundamental equations and concepts of electromagnetics are summarized in order to facilitate the demonstration of the unified approach. Our aim is to provide students, designers, and researchers with a framework for developing new numerical algorithms, to guide users in the selection and application of electromagnetic design tools, and to foster informed engineering judgment. This article also serves as a review and summary of earlier theoretical works reported in different places and at different times.

The Discrete Dipole Approximation: A Review

Abstract: There are many methods for rigorously calculating electromagnetic diffraction by objects of arbitrary shape and permittivity. In this article, we will detail the discrete dipole approximation (DDA) which belongs to the class of volume integral methods. Starting from Maxwell’s equations, we will first present the principle of DDA as well as its theoretical and numerical aspects. Then, we will discuss the many developments that this method has undergone over time and the numerous applications that have been developed to transform DDA in a very versatile method. We conclude with a discussion of the strengths and weaknesses of the DDA and a description of the freely available DDA-based electromagnetic diffraction codes.

Conversion Matrix Method of Moments for Time-Varying Electromagnetic Analysis

Abstract: A conversion matrix approach to solving network problems involving time-varying circuit components is applied to the method of moments for electromagnetic scattering analysis. Detailed formulations of this technique's application to the scattering analysis of structures loaded with time-varying circuit networks or constructed from general time-varying media are presented. The computational cost of the method is discussed, along with an analysis of compression techniques capable of significantly reducing computational cost for partially loaded systems. Several numerical examples demonstrate the capabilities of the technique along with its validation against conventional methods of modeling time-varying electromagnetic systems, such as finite difference time domain and transient circuit co-simulation.

Electromagnetic Modeling of Lossy Materials With a Potential-Based Boundary Element Method

Abstract: The boundary element method (BEM) enables solving three-dimensional electromagnetic problems using a two-dimensional surface mesh, making it appealing for applications ranging from electrical interconnect analysis to the design of metasurfaces. The BEM typically involves the electric and magnetic fields as unknown quantities. Formulations based on electromagnetic potentials rather than fields have garnered interest recently, for two main reasons: (a) they are inherently stable at low frequencies, unlike many field-based approaches, and (b) potentials provide a more direct interface to quantum physical phenomena. Existing potential-based formulations for electromagnetic scattering have been proposed primarily for perfect conductors. We develop a potential-based BEM formulation which can capture both dielectric and conductive losses, and accurately models the skin effect over broad ranges of frequency. The accuracy of the proposed formulation is validated through canonical and realistic numerical examples.

Description of Microwave Circuits via the Reduced-Basis Method Giving Physical Insight

Abstract: A description of electromagnetics by means of the reduced-basis method (RBM), which gives physical insight, is detailed. Contrary to what has been previously done to get further insights from the electromagnetic behavior, a reliable reduced-order model completely describing a microwave circuit in a frequency band of interest is carried out. Following a theoretical analysis starting from time-harmonic Maxwell’s equations, we identify the dominant contributions to electromagnetics in a band of analysis. Making use of the reliable reduced-order model, we present the electromagnetic information in that reduced-order model in a more insightful manner, using a specific dynamical system representation of electromagnetics. As a result, a full-wave coupling matrix completely describing electromagnetics in the band of analysis is identified, where no narrowband approximation is considered, such as it is the case in classical coupling matrix circuit theory. No approximation is taken into account other than carrying out the analysis in a given frequency band, which can be arbitrarily large. The proposed approach provides a way to understand electromagnetics, where a full-wave coupling matrix allows the description of electromagnetics in a band of interest as a simple physically insightful circuit, and not the other way around. Finally, several real-life microwave circuits, such as a dual-mode filter and diplexer, will illustrate the capabilities and efficiency of the proposed approach.

Numerical modeling of EM scattering from plasma sheath: A review

Abstract: Plasma generated by hypersonic aerocraft is one of the research subjects in computational electromagnetics. When the aerocraft flies at an ultra-high speed in the near space, plasma sheath will be generated in the surroundings and it will trigger varying changes in aerocraft radar electromagnetic scattering properties. Plasma sheath brings about tremendous impacts on the communication between the aerocraft and the outside world, and even ends with "blackout effects" to interrupt communication in severe cases. The interplay between the plasma sheath and the electromagnetic wave involves multiple disciplines covering aerodynamics, plasma sheath physics, and electromagnetic field theory. Therefore, it is challengeable to build a rigorous numerical modeling of the plasma sheath. In this paper, the latest technologies in the electromagnetic simulation of hypersonic aerocraft with plasma sheath are reviewed. Applied cases review and illustrate extensive approaches from approximate calculations to accurate calculations, including analytical methods, differential equation methods, integral equation methods and high-frequency approximation methods. The paper assesses the RCS of electromagnetic wave in analyzing the electromagnetic scattering problem in plasma. With the considerations the reality of electromagnetic simulation and future challenges, the paper talks about the efficiency, advantages and disadvantages of these approaches in simulating hypersonic aerocraft targets.

3-D Inversion of Airborne Electromagnetic Method Based on Footprint-Guided CFEM Modeling

Abstract: We investigate an algorithm for the 3-D inversion of frequency-domain airborne electromagnetic (AEM) data based on the forward modeling and sensitivity calculation by footprint-guided compact finite element method (CFEM). Unlike the conventional approach, the modeling volume in our algorithm for each transmitter–receiver pair is a regular hexahedral that encloses the footprint, rather than a large mesh for the entire survey area or the local mesh with a number of grids extending from the footprint. After the electric fields in the modeling volume are solved by vector finite element method (FEM) with an integral equation boundary condition, the response and sensitivity are explicitly calculated by employing the product of the prepared Green’s functions and the vector of electric fields. The accuracy of this footprint-guided CFEM is validated by comparing it against conventional CFEM, and different synthetic models are tested by our inversion algorithm. The inversion tests of synthetic models show the feasibility of the combination of footprint-guided CFEM and Gauss–Newton optimization in recovering models within an acceptable error level, and the inversion results show a good agreement with the true models on both the model geometry and recovered conductivity.

Iso-Geometric Integral Equation Solvers and Their Compression via Manifold Harmonics

Abstract: The state of the art of electromagnetic integral equations has seen significant growth over the past few decades, overcoming some of the fundamental bottlenecks: computational complexity, low-frequency breakdown, dense-discretization breakdown, preconditioning, and so on. Likewise, the community has seen extensive investment in the development of methods for higher order analysis, in both geometry and physics. Unfortunately, these standard geometric descriptors are continuous, but their normals are discontinuous at the boundary between triangular tessellations of control nodes, or patches, with a few exceptions; as a result, one needs to define additional mathematical infrastructure to define physical basis sets for vector problems. In stark contrast, the geometric representation used for design is second order differentiable almost everywhere on the surfaces. Using these descriptions for analysis opens the door to several possibilities, and is the area we explore in this article. Our focus is on loop subdivision-based isogeometric methods. In this article, our goals are twofold: 1) development of computational infrastructure for isogeometric analysis of electrically large simply connected objects, and 2) introduction of the notion of manifold harmonic transforms and its utility in computational electromagnetics. Several results highlighting the efficacy of these two methods are presented.

Modeling of Metasurfaces Using Discontinuous Galerkin Time-Domain Method Based on Generalized Sheet Transition Conditions

Abstract: A new discontinuous Galerkin time-domain (DGTD) method based on generalized sheet transition conditions (GSTCs) for analyzing the transient response of electromagnetic metasurfaces is presented. The discontinuities in electromagnetic fields around the vicinity of the metasurface are modeled by placing virtual edges on both sides of the metasurface. The GSTCs are incorporated in the updating equations of the standard DGTD algorithm by integrating the time-domain GSTCs formula with Galerkin’ s-weighted residual method. The DGTD-GSTC formulation can also simulate a bf piecewise linear approximation of a curved metasurfaces due to the unstructured mesh. This is the first time that DGTD is applied to the simulation of GSTCs. The implementation of this new method is verified by numerical cases.

Transient Analysis Method for Plasmonic Devices by PMCHWT With Fast Inverse Laplace Transform

Abstract: The transient analysis of electromagnetic problems is important in the designing of plasmonic devices. It is useful for clarifying physical phenomena with extremely short timescales, because transient response affects the device performance. A time-domain computational technique is proposed for the transient analysis of electromagnetic problems with nanostructures. Our method is based on boundary integral equations in the complex frequency domain and fast inverse Laplace transforms. The advantage of our method is that the objects can be modeled by surface structure, dispersive media can be easily considered, computational error analysis is simple, and the electromagnetic field at the desired observation time can be obtained.

Expedited Variable-Resolution Surrogate Modeling of Miniaturized Microwave Passives in Confined Domains

Abstract: The design of miniaturized microwave components is largely based on computational models, primarily, full-wave electromagnetic (EM) simulations. The EM analysis is capable of giving an accurate account for cross-coupling effects, substrate and radiation losses, or interactions with environmental components (e.g., connectors). Unfortunately, direct execution of EM-based design tasks, such as parametric optimization or uncertainty quantification (UQ), may turn prohibitively expensive in computational terms. A workaround has been offered by surrogate-assisted procedures that capitalize on replacing expensive EM simulations by fast metamodels, notably data-driven ones. However, the construction of general-purpose metamodels is impeded by the curse of dimensionality as well as a limited capability of approximation techniques to represent highly nonlinear responses of microwave devices. This article proposes a novel technique that integrates the performance-driven modeling paradigm as well as variable-resolution EM simulations. The former focuses on the construction of the surrogate in the parameter space subset encompassing high-quality designs, which effectively addresses the dimensionality issues. The latter—realized through co-kriging—contributes to further computational savings by executing the majority of circuit evaluations at the level of coarse-discretization EM analysis. Verification experiments conducted for three microstrip components demonstrate the superiority of the proposed approach over existing performance-driven techniques, let alone conventional modeling procedures, both with respect to accuracy and computational cost of the surrogate construction.

A Computational Electromagnetics and Sparsity-Based Feature Extraction Approach to Ground-Penetrating Radar Imaging

Abstract: In this paper, a feature extraction technique based on the electromagnetic representation of radar signals is presented. In particular, we focus on ground penetrating radar imaging, where we model the backscatter from varying two dimensional geometric shapes with arbitrary local coordinate rotations. Due to the electrically small nature of buried targets, and the bending of the radar signal at the air-soil interface we focus on exact methods to model the surface current density induced on scattering surfaces. Overcomplete basis sets are derived from the electromagnetic descriptions to represent the scene in a sparse manner. From this proposed modeling framework we devise a novel methodology to exploit the prediction of scattering behavior to extract features for classification from radar scenes when multiple buried scattering surfaces are present. We see that our method can identify and reconstruct buried scattering geometries in the presence of false targets that are brought about from the nonlinear nature of the exact electromagnetic modelling methods. A noniterative algorithm based on the conjugate of Green’s function is developed to solve for the surface current in an unknown domain using multi-frequency, multi-aperture data. Our modeling and feature extraction algorithms are numerically validated for different target shapes buried in lossy soil profiles.

Review of Least Action Principle in Electromagnetics: Part II: Derivation of Maxwell's Equations

Abstract: The 2nd paper in three-part study deals with a derivation of Maxwell's equations by using Hamilton's principle in electromagnetics and Noether's theorem for fields. Kinematical Maxwell's equations are derived from gauge symmetry, while two dynamical Maxwell's equations are derived by minimizing the functional of electromagnetic energy. The corresponding Lagrangian is given as difference between energy stored in the magnetic and electric field respectively.

Computational Electromagnetics for Industrial Applications

Abstract: Nowadays, computational electromagnetics (CEMs) methods play an important role in the rapid modeling and design of electromagnetic (EM) systems and their industrial applications [...]

Development of IEEE P2816: Recommended Practice for Computational Electromagnetics Applied to Modeling and Simulation of Antennas

Abstract: The Antennas and Propagation Standards Committee (APS/SC) is developing a recommended practice for computational electromagnetics (CEM) applied to modeling and simulation of antennas (P2816). The draft standard presents commonly used CEM methods: integral equations and method of moments (MoM), finite element method (FEM), finite difference time domain (FDTD) method and Transmission Line Matrix (TLM) method. For practicality of the standard, it additionally includes benchmark problems as examples for the potential users. The biconical antenna was proposed as a benchmark problem and for an international interlaboratory comparison. It is herein described with a comparison of some preliminary results.

An Augmented Y-parameter Method for Macromodeling Electromagnetic Structures in the Presence of Plane-Waves

Abstract: This work presents a novel modeling approach to characterize microwave structures in the presence of external electromagnetic waves. The method relies on augmenting traditional network parameters such as Y-parameters with an increased number of columns to account for the inclusion of Vector Spherical Wave Functions (VSWFs) in the voltage vector. Once extracted, the proposed augmented Y-parameter model can then be used for real-time computation of port currents corresponding to numerous parametric changes that can alter the incident wave, thereby aiding in rapid circuit design and optimization exercises.

The Ping-Pong Electromagnetic Algorithm for Reflecting Surface Antennas of Arbitrary Shapes

Abstract: An efficient ping-pong algorithm is presented to deal with electromagnetic scattering from reflecting surface antennas such as the reconfigurable intelligent surfaces (RISs) of arbitrary geometric shapes. The proposed computational electromagnetics (CEM) algorithm does not require formation, storage, and inverse of the impedance matrix used by the method of moments (MoM). Instead, a rigorous formula is obtained for the computation of the surface current from the scattered electric field. Besides, the algorithm only contains convolution operations with the scalar Green’s function and second derivatives operations to iteratively update the surface currents and scattered electric field. Also, hypersingular integration arising from the singularities of the surface current and scattered electric field is properly regularized. Furthermore, the algorithm converges fast and satisfactory results are obtained after a few iterations, and it is about ten times as fast as the MoM. Besides, the first iteration gives the solution for reflecting surface antennas on substrates of perfect absorption. Numerical solutions are obtained for some typical antennas and comparisons are made to those in the literature and from the MoM.

Metrological and numerical Validation of electromagnetic Sub-Model Techniques for 3D-FEM

Abstract: Sub-model approaches for electromagnetic finite element analyses offer opportunities of efficiently analyzing smaller regions in high detail influenced by magnetic field arising over much larger domains. A novel sub-model technique allowing transient analysis with non-linear materials in three-dimensional space is validated through comparisons with the results obtained by measurements and by employing conventional finite element approaches. As an example, an end-zone of a turbogenerator is investigated by studying different open and short circuit conditions. Comparisons are carried out in time and frequency domains.

Inversion of P-Band Electromagnetic Parameters Based on a Genetic Algorithm and Method of Moments

Abstract: Considering the difficulty in measuring the P-band electromagnetic parameters of porous materials such as graphene foam (GF), this paper proposes a free-space frequency-domain technology to measure the electrical properties of finite-plate materials from multiple perspectives. First, the multiangle reflectance of the sample was measured with the arch method; second, an electromagnetic simulation model consistent with the sample size was established, and the reflectance of different angles was calculated using the method of moments (MoM). Finally, the genetic algorithm (GA) was optimized for the electromagnetic parameters such that the reflective difference between the electromagnetic simulation model and the test obtained was minimized. The validity of the method was verified by reconstructing the electromagnetic parameters of a 1 m×1 m×0.03 m absorbing material at 0.5 GHz. The unique advantage of this method is that it solves the problem of inversion of electromagnetic parameters based on the multiangle reflectivity of an absorbing material plate within three times the wavelength. Because the electromagnetic simulation model can automatically divide the appropriate mesh size according to the size of the electromagnetic parameters, this method is suitable for high-loss and low-loss materials. In addition, this method avoids the special processing requirements regarding the shape size of the absorbing material, which has a wide application scope and low cost.

Decoupled Potential Integral Equation for Electromagnetic Scattering From Arbitrarily Shaped Dielectric Objects

Abstract: Recently, integral equation formulations that use potentials as opposed to fields as unknown quantities have been developed for scattering from dielectric objects. It has been shown that these formulations can be construed so that they are well-conditioned across a broad frequency spectrum, a result that has been theoretically proven for spherical systems. Unfortunately, to date, this formulation has not been implemented on practical discretizations of objects. This is the goal of this article. Specifically, we present a well-conditioned and well-tested decoupled potential integral equation (DPIE) formulation and all the necessary implementation details for electromagnetic scattering from homogeneous, dielectric, arbitrarily shaped objects. The resulting decoupled systems do not suffer from low-frequency breakdown. Results that demonstrate these properties are presented for a number of different dielectric targets. Furthermore, in order to fully validate each of the two integral equations for the potentials, we develop analytical solutions for spherical systems.

A Normal-vector-field-based Preconditioner for a Spatial Spectral Domain-integral Equation Method for Multi-Layered Electromagnetic Scattering Problems

Abstract: |A normal-vector-(cid:12)eld-based block diagonal-preconditioner for the spatial spectral integral method is proposed for an electromagnetic scattering problem with multi-layered medium. This preconditioner has a block-diagonal matrix structure for both 2D TM polarization and 3D cases. Spectral analysis shows that the preconditioned system has a more clustered eigenvalue distribution, compared to the unpreconditioned system. For the cases with high contrast or negative permittivity, numerical experiments illustrate that the preconditioned system requires fewer iterations than the unpreconditioned system. The total computation time is reduced accordingly while the accuracy based on the normal-vector (cid:12)eld formulation of the solution is preserved.

An Efficient Model of High-Frequency Electromagnetic Field Coupling to Multiconductor Transmission Lines With the Presence of the Lossy Ground

Abstract: The modeling of the high-frequency electromagnetic field coupling to multiconductor transmission lines (MTLs) is the essential subject for the protection of power lines. When the wavelength of the electromagnetic wave is smaller than the cross sections between MTLs, the response of MTLs cannot be evaluated by the classical transmission line approximation. Even though the full-wave method can deal with this problem, it is time consuming to evaluate the response of long MTLs. This article presents a theory and an efficient method to solve the problem of the high-frequency electromagnetic field coupling to MTLs with the presence of the lossy ground. The asymptotic method, adopted for its high computational efficiency, is extended to obtain the solutions of MTLs above the lossy ground. The problem is solved semianalytically using the proposed method, which is much more computationally efficient in dealing with long MTLs. Several numerical examples are presented to validate the accuracy and efficiency of the proposed method.

HPC Geophysical Electromagnetics: A Synthetic VTI Model with Complex Bathymetry

Abstract: We introduce a new synthetic marine model for 3D controlled-source electromagnetic method (CSEM) surveys. The proposed model includes relevant features for the electromagnetic geophysical community such as large conductivity contrast with vertical transverse isotropy and a complex bathymetry profile. In this paper, we present the experimental setup and several 3D CSEM simulations in the presence of a resistivity unit denoting a hydrocarbon reservoir. We employ a parallel and high-order vector finite element routine to perform the CSEM simulations. By using tailored meshes, several scenarios are simulated to assess the influence of the reservoir unit presence on the electromagnetic responses. Our numerical assessment confirms that resistivity unit strongly influences the amplitude and phase of the electromagnetic measurements. We investigate the code performance for the solution of fundamental frequencies on high-performance computing architectures. Here, excellent performance ratios are obtained. Our benchmark model and its modeling results are developed under an open-source scheme that promotes easy access to data and reproducible solutions.

Csem Modelling Using High Order Fdtd on the Nonuniform Grid

Abstract: Summary We present a high-order finite-difference time-domain (FDTD) modelling method on nonuniform grids for 3D controlled-source electromagnetics (CSEM). The coefficients for our high-order finite-difference scheme are adaptively computed over the staggered nonuniform grid by inverting a Vandermonde matrix system. This crucial procedure greatly improves the accuracy compared with the 2nd order staggered scheme on nonuniform grid, which possesses only 1st order local truncation error due to centered differencing on non-equal spaced grids. Numerical examples demonstrate that our method is highly accurate and efficient.

Complex Inhomogeneous Dielectric Target Modeling and Scattering Estimation using a Self-Designed Software

Abstract: This paper presents a method to finely model the arbitrarily irregular-shaped and inhomogeneous dielectric target. The target is first geometrically divided into a set of homogeneous and isotropic tetrahedral regions. Each region is precisely matched with a set of electromagnetic parameters. As a result, this can accurately model the target which has an extremely complex dielectric constant distribution and an irregular shape. Regarding the electromagnetic scattering evaluation of the established model, the method of moments (MoM) is adopted in consideration of the coupling between these tetrahedral regions, and the total scattering is obtained by solving the matrix equation. The above two computational sections are integrated into a self-designed software. One can just input the spatial distribution of the dielectric constant and then the designed software automatically processes the target’s geometric information and meshes the target. Finally, the scattered electric field and radar cross section (RCS) of the target are output from the software. The designed software provides an effective and accurate way to study the electromagnetic scattering characteristics of the complex inhomogeneous objects.

Recent Advances in Multiphysics Parametric Modeling and Optimization of Microwave Components

Abstract: In the case of microwave components and systems, multi-physical domains in the real world, in addition to electromagnetic domains, will affect the system results. As a result, understanding how electromagnetic-centric multi-physics and systems interact is critical for accurate microwave component and system analysis. This work discusses progress in the investigation of low-cost electromagnetic-centric multi-physics parametric modeling of microwave components using space mapping technology and parallel electromagnetic-centric multi-physics optimization using transfer function. Two microwave filter examples demonstrate that these techniques are effective.