Showing papers on "Computational electromagnetics published in 2019"

custEM: Customizable finite-element simulation of complex controlled-source electromagnetic data

Abstract: We have developed the open-source toolbox custEM (customizable electromagnetic modeling) for the simulation of complex 3D controlled-source electromagnetic (CSEM) problems. It is based on t...

Optoelectronic Device Simulations Based on Macroscopic Maxwell–Bloch Equations

Abstract: Due to their intuitiveness, flexibility and relative numerical efficiency, the macroscopic Maxwell-Bloch (MB) equations are a widely used semiclassical and semi-phenomenological model to describe optical propagation and coherent light-matter interaction in media consisting of discrete-level quantum systems. This review focuses on the application of this model to advanced optoelectronic devices, such as quantum cascade and quantum dot lasers. The Bloch equations are here treated as a density matrix model for driven quantum systems with two or multiple discrete energy levels, where dissipation is included by Lindblad terms. Furthermore, the one-dimensional MB equations for semiconductor waveguide structures and optical fibers are rigorously derived. Special analytical solutions and suitable numerical methods are presented. Due to the importance of the MB equations in computational electrodynamics, an emphasis is placed on the comparison of different numerical schemes, both with and without the rotating wave approximation. The implementation of additional effects which can become relevant in semiconductor structures, such as spatial hole burning, inhomogeneous broadening and local-field corrections, is discussed. Finally, links to microscopic models and suitable extensions of the Lindblad formalism are briefly addressed.

Ultrafast Simulation and Optimization of Nanophotonic Devices with Integral Equation Methods

Abstract: Integrated photonics is poised to become a billion-dollar industry due to its vast array of applications. However, designing and modeling photonic devices remains challenging due to the lack of ana...

Challenges in the Electromagnetic Modeling of Road Embedded Wireless Power Transfer

Abstract: In this paper, starting from the experimental experience of the road embedment of a transmitting coil for wireless power transfer, a numerical model of such device is constructed. The model is then used to perform several parametric analyses which aim at investigating the influence of the main electromagnetic parameters of the concrete and the geometrical parameters of the wireless power transfer on the overall behavior of the device. The results of such study allow for providing guidelines for the design of the coil and the choice of the materials for the embedment. Moreover, as a secondary result of the adopted methodology, the electromagnetic characterization of the concrete adopted for the road embedment is obtained.

Assessing the Performance of Leja and Clenshaw-Curtis Collocation for Computational Electromagnetics with Random Input Data

Abstract: We consider the problem of quantifying uncertainty regarding the output of an electromagnetic field problem in the presence of a large number of uncertain input parameters. In order to reduce the growth in complexity with the number of dimensions, we employ a dimension-adaptive stochastic collocation method based on nested univariate nodes. We examine the accuracy and performance of collocation schemes based on Clenshaw-Curtis and Leja rules, for the cases of uniform and bounded, non-uniform random inputs, respectively. Based on numerical experiments with an academic electromagnetic field model, we compare the two rules in both the univariate and multivariate case and for both quadrature and interpolation purposes. Results for a real-world electromagnetic field application featuring high-dimensional input uncertainty are also presented.

Evaluation of 4-D Reaction Integrals Via Double Application of the Divergence Theorem

Abstract: The use of the method of moments to solve surface integral equations is one of the most popular numerical techniques in electromagnetic modeling and analysis. This method requires the accurate and efficient numerical evaluation of iterated surface integrals over both source and testing domains. In this paper, we propose a scheme for evaluating these 4-D interaction integrals between pairs of arbitrarily positioned and oriented elements. The approach is based on applying the surface divergence theorem twice, once on the source and once on the test domain. When the integrations are reordered as two outer contour integrals plus two inner radial integrals, the initial radial integrations provide significant smoothing of the underlying singular integrands. The method is numerically validated for static and dynamic kernels arising in the electric field integral equation, i.e., for kernels with $1/R$ singularities, and linear basis functions. The proposed formula to evaluate 4-D reaction integrals can be extended to different kernels and to different elements, e.g., to curved or volumetric elements, and to basis functions of higher order.

A block rational Krylov method for 3-D time-domain marine controlled-source electromagnetic modelling

Abstract: We introduce a novel block rational Krylov method to accelerate three-dimensional time-domain marine controlled-source electromagnetic modeling with multiple sources. This method approximates the time-varying electric solutions explicitly in terms of matrix exponential functions. A main attraction is that no time stepping is required, while most of the computational costs are concentrated in constructing a rational Krylov basis. We optimize the shift parameters defining the rational Krylov space with a positive exponential weight function, thereby producing smaller approximation errors at later times and reducing iteration numbers. Furthermore, for multi-source modeling problems, we adopt block Krylov techniques to incorporate all source vectors in a single approximation space. The method is tested on two examples: a layered seafloor model and a 3D hydrocarbon reservoir model with seafloor bathymetry. The modeling results are found to agree very well with those from 1D semi-analytic solutions and finite-element time-domain solutions using a backward Euler scheme, respectively. Benchmarks of the block rational Krylov method demonstrate that it can be as up to 10 times faster than backward Euler. The block method also benefits from better memory efficiency, resulting in considerable speedup compared to non-block methods.

Application of Two-Dimensional Discrete Dipole Approximation in Simulating Electric Field of a Microwave Breast Imaging System

Abstract: The 2-D electric field distribution of the microwave imaging system is numerically simulated for a simplified breast tumour model. The proposed two-dimensional discrete dipole approximation (DDA) has the potential to improve computational speed compared to other numerical methods while retaining comparable accuracy. We have modeled the field distributions in COMSOL Multiphysics as baseline results to benchmark the DDA simulations. We have also investigated the adequate sampling size and the effect of inclusion size and property contrast on solution accuracy. In this way, we can utilize the 2-D DDA as an alternative, fast, and reliable forward solver for microwave tomography. From a mathematical perspective, the derivation of the 2-D DDA and its application to microwave imaging is new and not previously implemented. The simulation results and the measurements show that the 2-D DDA is a well-grounded forward solver for the specified microwave breast imaging system.

Radiation and Scattering of an Arbitrarily Flanged Dielectric-Loaded Waveguide

Abstract: In this article, we present a new methodology in spectral domain to study a novel, complex canonical electromagnetic problem constituted of perfectly electrically conducting (PEC) wedges immersed in complex environments. In particular, we present an arbitrarily flanged dielectric-loaded waveguide that resembles practical structures in scattering analysis, radar applications, antenna’s design, and electromagnetic compatibility. The proposed method is based on the recently developed semianalytical method known as the generalized Wiener–Hopf technique that extends the applicability of classical Wiener–Hopf method to a new variety of problems constituted of different geometries and materials. In this article, the method is further extended and it is now capable of handling piecewise constant inhomogeneous dielectric layers by resorting to the application of characteristic Green’s function procedure starting from the wave equation. The method has the benefit to be a comprehensive mathematical model and to be quasi-analytical, thus allowing us to investigate the true physics of the problem in terms of field’s components. The proposed solution is also of interest in computational electromagnetics to benchmark numerical codes. Validation through numerical results is reported in terms of engineering quantities such as geometrical theory of diffraction (GTD)/uniform theory of diffraction (UTD) coefficients, total far fields, and modal fields.

Domain Uncertainty Quantification in Computational Electromagnetics

Abstract: We study the numerical approximation of time-harmonic, electromagnetic fields inside a lossy cavity of uncertain geometry. Key assumptions are a possibly high-dimensional parametrization of the unc...

An Efficient Footprint-Guided Compact Finite Element Algorithm for 3-D Airborne Electromagnetic Modeling

Abstract: The airborne electromagnetic (AEM) method is an efficient tool for assessing conductivity structures near the earth’s surface. The huge amounts of collected data over a survey area of tens to thousands of square kilometers result in an extremely high computational cost for rigorous modeling. Fortunately, for each transmitter and receiver (Tx–Rx) station, a volume of limited scale beneath the transmitter, called the footprint, contains the majority of the induced current and contributes most of the EM response at the receiver. In this letter, we develop a footprint-guided compact finite element method (CFEM), in which the inhomogeneous conductivity structure in the entire survey area is divided into small subareas based on the footprint so that the forward modeling for each subarea can be performed efficiently. The computational domain for every single Tx–Rx station consists of a small subarea and a surrounding layer. The accuracy of the algorithm is verified by comparing its solutions with semianalytical solutions on a layered earth model, and its applicability and efficiency are demonstrated with a more complex 3-D model consisting of a large inhomogeneous structure.

Optimized Nonuniform FFTs and Their Application to Array Factor Computation

Abstract: We deal with developing an optimized approach for implementing nonuniform fast Fourier transform (NUFFT) algorithms under a general and new perspective for 1-D transformations. The computations of nonequispaced results, nonequispaced data, and Type-3 nonuniform discrete Fourier transforms are tackled in a unified way. They exploit “uniformly sampled” exponentials to interpolate the “nonuniformly sampled” ones involved in the nonuniform discrete Fourier transforms (NUFDTs), so as to enable the use of standard fast Fourier transforms, and an optimized window. The computational costs and the memory requirements are analyzed, and their convenient performance is assessed also by comparing them with other approaches in the literature. Numerical results demonstrate that the method is more accurate and does not introduce any additional computational or memory burden. The computation of the window functions amounts to that of a Legendre polynomial expansion, i.e., a simple polynomial evaluation. This is convenient in terms of computational burden and of the proper arrangement of the calculations. A case study of electromagnetic interest has been carried out by applying the developed NUFFTs to the radiation of linear regular or irregular arrays onto a set of regular or irregular spectral points. Guidelines for multidimensional extension of the proposed approach are also presented.

Open-Source Software for Electromagnetic Scattering Simulation: The Case of Antenna Design

Abstract: Electromagnetic scattering simulation is an extremely wide and interesting field, and its continuous evolution is associated with the development of computing resources. Undeniably, antenna design at all levels strongly relies on electromagnetic simulation software. However, despite the large number and the high quality of the available open-source simulation packages, most companies have no doubts about the choice of commercial program suites. At the same time, in the academic world, it is frequent to develop in-house simulation software, even from scratch and without proper knowledge of the existing possibilities. The rationale of the present paper is to review, from a practical viewpoint, the open-source software that can be useful in the antenna design process. To this end, an introductory overview of the usual design workflow is firstly presented. Subsequently, the strengths and weaknesses of open-source software compared to its commercial counterpart are analyzed. After that, the main open-source packages that are currently available online are briefly described. The last part of this paper is devoted to a preliminary numerical benchmark for the assessment of the capabilities and limitations of a subset of the presented open-source programs. The benchmark includes the calculation of some fundamental antenna parameters for four different typologies of radiating elements.

Parallel Wideband MLFMA for Analysis of Electrically Large, Nonuniform, Multiscale Structures

Abstract: Electromagnetic scattering from electrically large objects with multiscale features is an increasingly important problem in computational electromagnetics. A conventional approach is to use an integral equation-based solver that is then augmented with an accelerator, a popular choice being a parallel multilevel fast multipole algorithm (MLFMA). One consequence of multiscale features is locally dense discretization, which leads to low-frequency breakdown and requires nonuniform trees. To the authors’ knowledge, the literature on parallel MLFMA for such multiscale distributions capable of arbitrary accuracy is sparse; this paper aims to fill this niche. We prescribe an algorithm that overcomes this bottleneck. We demonstrate the accuracy (with respect to analytical data) and performance of the algorithm for both PEC scatterers and point clouds as large as $755{\lambda }$ with several hundred million unknowns and nonuniform trees as deep as 16 levels.

Comparison of Numerical Techniques for the Evaluation of Human Exposure From Measurement Data

Abstract: Numerical dosimetry makes it possible to evaluate the influence of electromagnetic fields on the human body. The interest of performing numerical dosimetry starting from data coming from general purpose software or measurements is constantly growing. This paper compares two available methods that make dosimetry starting from the knowledge of the magnetic flux density. The quality of results is analyzed considering both exact and uncertain inputs stressing out when one method should be preferred over the other. Finally, the methods are validated using real measurements obtaining good results.

Efficient and Accurate Electromagnetic Modeling of Triaxial Induction Responses From Multiscale Fractures for Well-Logging Applications

Abstract: Electromagnetic modeling of triaxial induction responses in fractured formation is of growing importance in well-logging applications. Usually, fractures have a tiny thickness in a scale between micrometers and millimeters, while their length or width is several orders of magnitude larger than their thickness. Such a distinctive multiscale feature generally leads to a very dense mesh, which makes the modeling using the conventional methods, e.g., the finite element method and volume integral equation (VIE), unnecessarily expensive. With the aid of thin dielectric sheet (TDS) approximation for fractures, an efficient and accurate solution is achieved in this paper to model the triaxial induction responses by utilizing the TDS-based surface integral equation (TDS-SIE), which successfully transforms the original VIE into an SIE while guaranteeing a good accuracy. Since the TDS-SIE method only requires surface discretization, unnecessarily dense volume meshes are avoided, and a substantial amount of unknowns can be reduced in numerical simulation. By modeling the triaxial induction responses of both conductive and resistive fractures at the practical scenarios, excellent accuracy, efficiency, and flexibility of the TDS-SIE are demonstrated by comparing the result with that from the semianalytical one-dimensional solution or the VIE method. This provides a valuable solution to characterize near-borehole fractures from induction well-logging data.

Spectral-domain MOM for Planar Meta-materials of Arbitrary Aperture Wave-guide Array

Abstract: In this paper, an efficient Computational Electromagnetics (CEM) method based on Method of Moment (MOM) in the spectral domain with the wave-guide modes as test functions has been proposed for the planar meta-materials slab that consists of arbitrary aperture wave-guide or its periodic array. Starting from the equivalent surface electric and magnetic currents, we have derived rigorous Fourier spectra for both electric field and magnetic field. We then match the boundary conditions on the top and bottom surfaces of the planar meta-materials slab, from which we can obtain a system of MOM equations that are tested with the aperture wave-guide modes; and finally, we propose a matrix solution to solve the obtained MOM equations. In particularly, analytic formula has been obtained for the simple case of TE01 mode of the rectangular aperture wave-guide array and its physics meaning is explained. At last, numerical simulation is performed and result is presented.

Application of the semi-analytical Fourier transform to electromagnetic modeling.

Abstract: The Fast Fourier Transform (FFT) algorithm makes up the backbone of fast physical optics modeling. Its numerical effort, approximately linear on the sample number of the function to be transformed, already constitutes a huge improvement on the original Discrete Fourier Transform. However, even this orders-of-magnitude improvement in the number of operations required can fall short in optics, where the tendency is to work with field components that present strong wavefront phases: this translates, as per the Nyquist-Shannon sampling theorem, into a huge sample number. So much so, in fact, that even with the reduced effort of the FFT, the operation becomes impracticable. Finding a workaround that allows us to evade, at least in part, these stringent sampling requirements is then fundamental for the practical feasibility of the Fourier transform in optics. In this work we propose, precisely, a way to tackle the Fourier transform that eschews the sampling of second-order polynomial phase terms, handling them analytically instead: it is for this reason that we refer to this method as the "semi-analytical Fourier transform". We present here the theory behind this concept and show the algorithm in action at several examples which serve to illustrate the vast potential of this approach.

Electromagnetic modeling of high magnetic contrast media using Calderon preconditioning

Abstract: In this contribution, we present a Calderon preconditioner for a novel single-source equation to efficiently model electromagnetic scattering problems involving high magnetic contrasts. Through analysis of the spectral properties of the system matrix after discretization, it is shown that this formulation does not break down when high permeabilities are present, which was an unresolved problem of the Calderon preconditioned Poggio-Miller-Chan-Harrington-Wu-Tsai method. The adopted discretization scheme, which involves Rao-Wilton-Glisson and Buffa-Christiansen basis functions, allows for an easy integration in existing commercial Method of Moments software. The efficiency and accuracy of the presented method is corroborated by numerical examples. (C) 2018 Elsevier Ltd. All rights reserved.

Deterministic Constrained Synthesis Technique for Conformal Aperiodic Linear Antenna Arrays—Part II: Applications

Abstract: The aim of this paper is to illustrate the application of the antenna placement methodology introduced in Part I for the deterministic synthesis of general conformal aperiodic arrays subject to multiple concurrent design constraints on the relevant layout and excitation tapering, as it is typically the case in satellite communications and radar applications. Antenna mutual coupling is not considered in the developed methodology; hence, to assess the sensitivity of the design procedure to such nonideality, a dedicated investigation has been conducted using rigorous full-wave electromagnetic modeling and experimental measurements collected on physical prototypes. The obtained results demonstrate the effectiveness and versatility of the proposed array synthesis approach, even in operative scenarios in which a significant deviation from the desired antenna operation is observed.

Effective methods for optimal design of induction coils on example of surface hardening

Abstract: This paper aims to describe main ideas and demonstrates results of the research activities carried out by the authors in the field of optimal design concepts for induction heater for surface hardening. The main goal of the research studies is the application of different optimization methods and numerical finite element method (FEM) codes for field analysis to solve the optimal design problem that is mathematically formulated in terms of the one of the most important optimization criteria for surface hardening technology, e.g. maximum temperature uniformity within the hardening surface layer.,Evolutionary algorithm based on Adaptive Gaussian Process-Assisted Differential Evolution for MEMS Design Optimization (AGDEMO) and alternance method of parametric optimization based on optimal control theory are applied as effective tools for the practice-oriented problem for optimization of induction heater design based on non-linear coupled electromagnetic and temperature field analysis. Different approaches are used for combining FEM codes for interconnected field analysis and optimization algorithms into automated optimization procedure.,Optimization procedures are tested and investigated for optimal design problem solution on the examples of induction hardening of steel cylindrical billet.,Solved problems are based on the design of practical industrial applications. The developed optimization procedures are planned to be applied to the wide range of real-life problems of the optimal design of different electromagnetic devices and systems.,This paper describes main ideas and results of the research activities carried out by the authors in the field of optimal design of induction heaters for hardening based on numerical coupled electromagnetic and temperature field analysis. The implementation of the automated procedure that combines a numerical FEM code for coupled field analysis with an optimization algorithm and its subsequent application for designing induction heaters makes the proposed approach specific and original. This paper also demonstrates that different optimization strategies used (evolutionary algorithm based on AGDEMO and alternance method of optimal control theory) are effective for real-life industrial applications for optimization of induction heaters design.

Validation of Vibrating Intrinsic Reverberation Chamber using Computational Electromagnetics

Abstract: Our study demonstrates a validation of the computational electromagnetics modeling and a simulation of a vibrating intrinsic reverberation chamber (VIRC). The VIRC generates a random electromagnetic environment by shaking the flexible conductive walls to vary the boundary conditions. The finite-difference time-domain method was applied to model a VIRC and simulate its behavior. The VIRC's behavior was modeled using rough surfaces and multiple independent cavity models. We performed two statistical analyses for the numerical validation. First, the field distribution in the VIRC was evaluated using the chi-squared goodness-of-fit (GOF) test. Second, the spatial field uniformity was evaluated using the standard deviation of the maximum and the average of each orthogonal electric field magnitude within the defined working volume. These statistical analysis results indicated that a random electromagnetic environment in the VIRC could be simulated by applying multiple independent cavity models with three orthogonal rough surfaces.

The dominant exploration area from three-dimensional crosswell electromagnetic modeling in the time domain

Abstract: We analyze the sensitivity of a three-dimensional crosswell electromagnetic (EM) system based on finite-difference time-domain modeling. To reinforce the simulation accuracy of low-frequency electr...

Theory of soliton propagation in nonlinear photonic crystal waveguides

Abstract: Propagation of the temporal soliton in Kerr-type photonic crystal waveguide is investigated theoretically and numerically. An expression describing the evolution of the envelope of the soliton based on the full-wave modal analysis, taking into account all space-harmonics, is rigorously obtained. The nonlinear coefficient is derived, for the first time, based on a modification of the refractive indices for each space-harmonic due to the Kerr-type nonlinearity. For illustrating the general formulation and results, we performed extensive computational electromagnetics simulations for the propagation of gap solitons in an experimentally feasible photonic crystal waveguides, endorsing the correctness and usefulness of the proposed formalism.