Showing papers on "Computational electromagnetics published in 2008"
TL;DR: In this article, a square electromagnetic cloak and an omni-directional electromagnetic field concentrator are described and the functionality of the devices is numerically confirmed by two-dimensional finite element simulations.
Abstract: The technique of applying form-invariant, spatial coordinate transformations of Maxwell’s equations can facilitate the design of structures with unique electromagnetic or optical functionality. Here, we illustrate the transformation-optical approach in the designs of a square electromagnetic cloak and an omni-directional electromagnetic field concentrator. The transformation equations are described and the functionality of the devices is numerically confirmed by two-dimensional finite element simulations. The two devices presented demonstrate that the transformation optic approach leads to the specification of complex, anisotropic and inhomogeneous materials with well directed and distinct electromagnetic behavior.
770 citations
TL;DR: The use of Mie theory is described to determine electromagnetic contributions to SERS enhancements that include for retarded dipole emission effects, and the use of the quasistatic approximation for spheroidal particles interacting with dye adsorbate layers.
Abstract: This Account provides an overview of the methods that are currently being used to study the electromagnetics of silver and gold nanoparticles, with an emphasis on the determination of extinction and surface-enhanced Raman scattering (SERS) spectra. These methods have proven to be immensely useful in recent years for interpreting a wide range of nanoscience experiments and providing the capability to describe optical properties of particles up to several hundred nanometers in dimension, including arbitrary particle structures and complex dielectric environments (adsorbed layers of molecules, nearby metal films, and other particles). While some of the methods date back to Mie's celebrated work a century ago, others are still at the forefront of algorithm development in computational electromagnetics. This Account gives a qualitative description of the physical and mathematical basis behind the most commonly used methods, including both analytical and numerical methods, as well as representative results of applications that are relevant to current experiments. The analytical methods that we discuss are either derived from Mie theory for spheres or from the quasistatic (Gans) model as applied to spheres and spheroids. In this discussion, we describe the use of Mie theory to determine electromagnetic contributions to SERS enhancements that include for retarded dipole emission effects, and the use of the quasistatic approximation for spheroidal particles interacting with dye adsorbate layers. The numerical methods include the discrete dipole approximation (DDA), the finite difference time domain (FDTD) method, and the finite element method (FEM) based on Whitney forms. We discuss applications such as using DDA to describe the interaction of two gold disks to define electromagnetic hot spots, FDTD for light interacting with metal wires that go from particle-like plasmonic response to the film-like transmission as wire dimension is varied, and FEM studies of electromagnetic fields near cubic particles.
453 citations
TL;DR: A review of the higher-order computational electromagnetics (CEM) for antenna, wireless, and microwave engineering applications is presented in this article, focusing on frequency-domain solutions.
Abstract: A review of the higher order computational electromagnetics (CEM) for antenna, wireless, and microwave engineering applications is presented. Higher order CEM techniques use current/field basis functions of higher orders defined on large (e.g., on the order of a wavelength in each dimension) curvilinear geometrical elements, which greatly reduces the number of unknowns for a given problem. The paper reviews all major surface/volume integral- and differential-equation electromagnetic formulations within a higher order computational framework, focusing on frequency-domain solutions. With a systematic and unified review of generalized curved parametric quadrilateral, triangular, hexahedral, and tetrahedral elements and various types of higher order hierarchical and interpolatory vector basis functions, in both divergence- and curl-conforming arrangements, a large number of actual higher order techniques, representing various combinations of formulations, elements, bases, and solution procedures, are identified and discussed. The examples demonstrate the accuracy, efficiency, and versatility of higher order techniques, and their advantages over low-order discretizations, the most important one being a much faster (higher order) convergence of the solution. It is demonstrated that both components of the higher order modeling, namely, higher order geometrical modeling and higher order current/field modeling, are essential for accurate and efficient CEM analysis of general antenna, scattering, and microwave structures.
140 citations
TL;DR: In this paper, a matrix splitting algorithm is developed to break up the texture limit, which splits the huge matrix into multiple, tiny matrixes, each of which can be fit into one texture.
Abstract: The graphics processing unit (GPU) has been used to speed up the conventional method of moments (MoM) calculations for electromagnetic scattering from arbitrary three-dimensional conducting objects. The acceleration ratio of filling impedance matrix has reached 30, while the total acceleration ratio (including iteration) is about 20. Moreover, a matrix splitting algorithm is developed to break up the texture limit. It splits the huge matrix into multiple, tiny matrixes, each of which can be fit into one texture. Then, the system memory can be used to store all the elements of the impedance matrix, making it possible to deal with electrically large problems, since the capacity of video card's memory is no longer a limit.
97 citations
TL;DR: In this article, the authors proposed a novel numerical method to simulate transient electromagnetic problems, where the fields at the collocation points are expanded into a series of radial basis functions and are treated with a meshless method procedure.
Abstract: We propose a novel numerical method to simulate transient electromagnetic problems. The time derivatives are still tackled with the customary explicit leapfrog time scheme. But in the space domain, the fields at the collocation points are expanded into a series of radial basis functions and are treated with a meshless method procedure. Our method solves numerically Maxwell's equations with various assigned boundary conditions and current source excitation. Furthermore, the numerical stability condition of our method is obtained through a one-dimensional (1-D) wave equation and thus the relationship between control parameters is accounted for. To verify the accuracy and effectiveness of the new formulation, we compare the results of the proposed method with those of the conventional finite-difference time-domain method through a 1-D case study with different boundary conditions.
96 citations
TL;DR: In this paper, the authors studied the properties of surface integral equations of the first and second kinds in electromagnetic scattering and radiation problems and found that the second-kind equations gave better conditioned matrix equation and faster converging iterative solutions but poorer solution accuracy than the first-kind equation.
Abstract: Properties of various surface integral equations of the first and second kinds are studied in electromagnetic scattering and radiation problems. The second-kind equations are found to give better conditioned matrix equation and faster converging iterative solutions but poorer solution accuracy than the first-kind equations. The solution accuracy and matrix conditioning seem to be almost opposite properties associated with the singularity of the kernel of integral operators. The more singular/smoother the kernel, the more/less diagonally dominant and the better/poorer conditioned the matrix, but the poorer/better the solution accuracy. Accuracy of the integral equations of the second kind can be improved by increasing the order of the basis and testing functions. However, the required expansion order seems to be problem dependent. The more singular the unknown, the higher the expansion order and the finer the discretization needed in order to maintain the solution accuracy of the second-kind equations.
94 citations
TL;DR: An iterative scheme for the rigorous computation of electrically large problems is presented that can deal with very large problems that require an iterative solution process, even considering that the application of the CBFM entails an important reduction of the number of unknowns when compared to Method of Moments approaches based on subdomain functions.
Abstract: An iterative scheme for the rigorous computation of electrically large problems is presented. The approach is based on a combination of the characteristic basis function method (CBFM) and the multilevel fast multipole algorithm (MLFMA) that can deal with very large problems that require an iterative solution process, even considering that the application of the CBFM entails an important reduction of the number of unknowns when compared to Method of Moments approaches based on subdomain functions. This reduction is due to the fact that the number of macro-basis functions, called characteristic basis functions (CBFs), is lesser than the number of low-level subsectional functions used to sample the geometry. In addition, the use of the MLFMA avoids the need to calculate and store the coupling terms in the reduced matrix that are not on or close to the diagonal, thereby optimizing the CPU time and the memory storage requirements. non-uniform rational B-splines (NURBS) surfaces are employed for the representation of the geometry and the CBFs are described in terms of curved rooftops generated in the parametric space. The associated macro-testing functions are defined as aggregations of curved razor-blade functions.
85 citations
15 Jun 2008
TL;DR: The mathematical background of the radial point interpolation method and a two-dimensional implementation are presented and it is shown that solutions converge much faster using the ability of conformal modeling compared to a similar analysis in rectangular grids.
Abstract: A meshless numerical technique based on radial point interpolation is introduced for electromagnetic simulations in time domain. The general class of meshless methods presents very attractive properties for addressing future challenges of electromagnetic modeling. Among the interesting aspects, the ability to handle arbitrary node distributions for conformal and multi-scale modeling can be mentioned first. Furthermore, the possibility of modifying the node distribution dynamically opens new perspectives for adaptive computations and optimization. The mathematical background of the radial point interpolation method and a two-dimensional implementation are presented here. The advantages of this meshless method are discussed and applied to a model consisting of a 90 degree H-plane waveguide bend. It is shown that solutions converge much faster using the ability of conformal modeling compared to a similar analysis in rectangular grids.
80 citations
TL;DR: An efficient parallelization scheme is obtained when multiple dielectric objects are involved in the simulation, and a better spreading of the communication through time is obtained, avoiding both communication in bursts and synchronization at each MLFMA level.
Abstract: In this paper, a new strategy for the parallelization of the multilevel fast multipole algorithm (MLFMA) on distributed memory computers is presented. By using an asynchronous implementation of the parallel MLFMA, an efficient parallelization scheme is obtained when multiple dielectric objects are involved in the simulation. Furthermore, a better spreading of the communication through time is obtained, avoiding both communication in bursts and synchronization at each MLFMA level. This proves especially beneficial when slower interconnection networks are used.
77 citations
TL;DR: It is proposed to replace SPM with the first-order small-slope approximation (SSA1) to treat the small-scale roughness and derive the formulas for the corresponding TSM, referred to as GO-SSA, which is robust to the choice of the frequency cutoff and given a numerical illustration for the sea surface.
Abstract: The two-scale model (TSM) is one of the most frequently employed approaches in scattering from multiscale surfaces such as ocean surfaces. It consists of combining geometrical optics (GO) with the small-perturbation model (SPM) to be able to cope with both the small- and large-scale components of the surface. However, well-known shortcomings of this method are the arbitrariness of the dividing scale and the sensitivity of the scattering cross section to the choice of this parameter. We propose to replace SPM with the first-order small-slope approximation (SSA1) to treat the small-scale roughness and derive the formulas for the corresponding TSM, referred to as GO-SSA. We show that GO-SSA is robust to the choice of the frequency cutoff and give a numerical illustration for the sea surface.
74 citations
TL;DR: A hybrid algorithm, based on the overlapped domain decomposition method for integral equations, MLFMA and block-diagonal, incomplete lower and upper triangular matrices (DILU) preconditioner, is proposed for the analysis of electrically large problems and is more suitable for analyzing very large EM scattering problems.
Abstract: For electrically large complex electromagnetic (EM) scattering problems, huge memory is often required for most EM solvers, which is too difficult to be handled by a personal computer (PC) even a workstation. Although the multilevel fast multipole algorithm (MLFMA) effectively deals with electrically large problems to some extent, it is still time and memory consuming for very large objects. In order to further reduce the CPU time and the memory requirement, a hybrid algorithm, based on the overlapped domain decomposition method for integral equations (IE-ODDM), MLFMA and block-diagonal, incomplete lower and upper triangular matrices (DILU) preconditioner, is proposed for the analysis of electrically large problems. The dominant memory requirement for plane wave expansions in the three processes of aggregation, translation and disaggregation in the MLFMA is drastically reduced by the first two techniques. The iterative procedure for each overlapped subdomain solved by the MLFMA is effectively sped up by the DILU preconditioner. After integrating these techniques, the proposed hybrid algorithm is more efficient in computing time and memory requirement compared to the conventional MLFMA and is more suitable for analyzing very large EM scattering problems. Enough accurate solution can be obtained within quite a few outer iterations, where an outer iteration means a complete sweep for all the subdomains. Some numerical examples are presented to demonstrate its validity and efficiency.
TL;DR: In this paper, a survey of high-order symplectic finite-difference time-domain schemes, which use th-order integration time stepping and thorder staggered space differencing, is presented.
Abstract: To discretize Maxwell's equations, a variety of high-order symplectic finite-difference time-domain schemes, which use th-order symplectic integration time stepping and th-order staggered space differencing, are surveyed. First, the order conditions for the symplectic integrators are derived. Second, the comparisons of numerical stability, dispersion, and energy-conservation are provided between the high-order symplectic schemes and other high-order time approaches. Finally, these symplectic schemes are studied by using different space and time strategies. According to our survey, high-order time schemes for matching high-order space schemes are required for optimum electromagnetic simulation. Numerical experiments have been conducted on radiation of electric dipole and wideband S-parameter extraction of dielectric-filled waveguide. The results demonstrate that the high-order symplectic scheme can obtain satisfying numerical solutions under high Courant-Friedrichs-Levy number and coarse grid conditions.
TL;DR: In this article, a review of electromagnetic models of the lightning return stroke is presented, with an emphasis on their applications in light of the fact that electromagnetic models allow a self-consistent full-wave solution for both current distribution along the lightning channel and associated electromagnetic fields.
Abstract: Lightning return-stroke models are needed to study lightning effects on various objects and systems, as well as in characterizing the lightning electromagnetic environment. Reviewed here are models based on Maxwell's equations and referred to as electromagnetic models. In contrast to distributed-circuit and so-called engineering models, electromagnetic models of the lightning return stroke allow a self-consistent full-wave solution for both current distribution along the lightning channel and associated electromagnetic fields. In this paper, we review electromagnetic models with an emphasis on their applications.
TL;DR: The tree structure of MLFMA is distributed among the processors by partitioning both the clusters and the samples of the fields appropriately for each level, and the parallelisation efficiency is significantly improved compared to previous approaches.
Abstract: A hierarchical parallelisation of the multilevel fast multipole algorithm (MLFMA) for the efficient solution of large-scale problems in computational electromagnetics is presented The tree structure of MLFMA is distributed among the processors by partitioning both the clusters and the samples of the fields appropriately for each level The parallelisation efficiency is significantly improved compared to previous approaches, where only the clusters or only the fields are partitioned in a level
TL;DR: It is shown that the conformal PML can be easily incorporated into the mixed FETD algorithm by utilizing PML constitutive tensors whose discretization is naturally decoupled from that of Maxwell curl equations (spatial derivatives).
Abstract: We introduce a conformal perfectly matched layer (PML) for the finite-element time-domain (FETD) solution of transient Maxwell equations in open domains. The conformal PML is implemented in a mixed FETD setting based on a direct discretization of the first-order coupled Maxwell curl equations (as opposed to the second-order vector wave equation) that employs edge elements (Whitney 1-form) to expand the electric field and face elements (Whitney 2-form) to expand the magnetic field. We show that the conformal PML can be easily incorporated into the mixed FETD algorithm by utilizing PML constitutive tensors whose discretization is naturally decoupled from that of Maxwell curl equations (spatial derivatives). Compared to the conventional (rectangular) PML, a conformal PML allows for a considerable reduction on the amount of buffer space in the computational domain around the scatterer(s).
TL;DR: The proposed simulator significantly extends the capability of the existing time-domain finite element solver to model more complex and active devices such as microwave amplifiers.
Abstract: A symmetric hybrid electromagnetic-circuit simulator based on the extended time-domain finite element method (FEM) is presented for the simulation of microwave devices embedded with linear/nonlinear lumped circuits. The distributive portion of the device is modeled by the time-domain FEM to generate an electromagnetic subsystem, while the embedded lumped circuits are analyzed by a SPICE-like transient circuit solver to generate a circuit subsystem. A symmetric global system for both the electromagnetic and circuit unknowns is then established by combining the two fully discretized subsystems through coupling matrices to model their interactions. For active devices, the resulting global electromagnetic-circuit system usually includes nonlinear equations, and thus is solved by a solution algorithm carefully designed to handle nonlinearity. The proposed simulator significantly extends the capability of the existing time-domain finite element solver to model more complex and active devices such as microwave amplifiers. Numerical examples are presented to validate the algorithm and demonstrate its accuracy and applications.
TL;DR: In this article, a general formulation for the time-domain partial element equivalent circuit method in a general dispersive medium is presented based on Debye and Lorentz models where the resulting model is passive.
Abstract: In this paper a general formulation is presented for the time-domain partial element equivalent circuit method in a general dispersive medium. The formulation is based on Debye and Lorentz models where the resulting model is passive. The incorporation of such models into a partial element equivalent circuit solver is described by both convolution techniques and equivalent circuits. The new circuit models can be applied in the frequency as well as the time domain. Numerical examples are given to validate the proposed formulation and to show that the proposed method is accurately capturing the physics of dispersive and lossy dielectrics.
TL;DR: This paper presents a computationally efficient approach to performing electromagnetic simulations in the presence of statistically defined uncertainties caused by either material in- homogeneities, or fabrication and placement tolerances.
Abstract: This paper presents a computationally efficient approach to performing electromagnetic simulations in the presence of statistically defined uncertainties caused by either material in- homogeneities, or fabrication and placement tolerances. Comparisons are made with results from Monte Carlo simulations and a sequence of higher order approximation extensions to the technique. It is shown that accurate results are possible within practical computational limits for the case of small parameter variations.
TL;DR: An efficient algorithm based on domain decomposition method (DDM) and partial basic solution vectors (PBSV) technique is proposed for solving three-dimensional (3-D), large-scale, finite periodic electromagnetic problems, such as photonic or electromagnetic bandgap structures, frequency selective surfaces.
Abstract: An efficient algorithm based on domain decomposition method (DDM) and partial basic solution vectors (PBSV) technique is proposed for solving three-dimensional (3-D), large-scale, finite periodic electromagnetic problems, such as photonic or electromagnetic bandgap structures, frequency selective surfaces. The entire computational domain is divided into many smaller nonoverlapping subdomains. A Robin-type condition is introduced at the interfaces between subdomains to enforce the field continuity. With the help of a set of dual unknowns, each subdomain can be tackled independently. Because of geometric repetitions, all the sudomains can be classified into a few building blocks, which can be dealt with by an improved PBSV algorithm. Thus, the original problem becomes a much smaller one which involves the unknowns only at the interfaces. The resulting linear system of equations is solved by a block symmetric successive over relaxation (SSOR) preconditioned Krylov subspace method. Once the unknowns at the interfaces have been obtained, the final solution on each subdomain can easily be calculated independently. Some numerical examples are provided and show the method is scalable with the number of subdomains.
TL;DR: A new approach based on generating low-dimensional simulation models that approximate the original spatially discretized models of electromagnetic field and their variations under conditions of component movement and material nonlinearity is presented.
Abstract: We present a new approach for generating fast simulation models of electromagnetic (EM) devices that contain moving components and magnetic materials with nonlinear properties. Our approach is based on generating low-dimensional simulation models that approximate the original spatially discretized models of electromagnetic field and their variations under conditions of component movement and material nonlinearity. The movement of the modeled device components is simulated by coupling the reduced-order EM field models weakly to the mechanical equations. We have successfully used our approach to generate a fast simulation model of a simple electromagnetic device with a moving component and nonlinear material properties.
TL;DR: It is demonstrated that the optimization procedure can also be used to provide beam-steering ability to LP arrays and the directive gain is stabilized in the operation band using optimization by genetic algorithms.
Abstract: Circular arrays of log-periodic (LP) antennas are designed and their operational properties are investigated in a sophisticated simulation environment that is based on the recent advances in computational electromagnetics. Due to the complicated structures of the trapezoidal-tooth array elements and the overall array configuration, their analytical treatments are prohibitively difficult. Therefore, the simulation results presented in this paper are essential for their analysis and design. We present the design of a threeelement LP array showing broadband characteristics. The directive gain is stabilized in the operation band using optimization by genetic algorithms. We demonstrate that the optimization procedure can also be used to provide beam-steering ability to LP arrays.
TL;DR: Numerical results favorably compare with numerical and experimental data and proves the usefulness of the method to model UXOs in clutter-contaminated soils, and the optimization approach used to match the numerical predictions with experimental data demonstrates the possibility of remotely inferring the material properties of objects.
Abstract: The secondary field produced by 3-D highly permeable and conductive objects is computed in the electromagnetic induction regime, with the purpose of modeling unexploded ordnances (UXOs) and surrounding clutter. The analytical formulation is based on the ellipsoidal coordinate system that is able to model real 3-D geometries as opposed to bodies of revolutions like within a spheroidal approach. At the frequencies of interest (tens of hertz to hundreds of kilohertz), conduction currents in the soil are negligible, and the fields are computed in the magnetoquasistatic regime based on the Laplace equation. Inside the objects, where the wave equation governs the field distribution, the currents are assumed to have a small penetration depth, allowing for the analytical simplification of the field components, which become decoupled at the surface. This approximation, which is valid across the entire frequency spectrum because of the high permeability and conductivity, avoids the necessity of using ellipsoidal wave functions and results in a considerable saving of computational time. Numerical results favorably compare with numerical and experimental data, which proves the usefulness of our method to model UXOs in clutter-contaminated soils. Finally, the optimization approach used to match our numerical predictions with experimental data demonstrates the possibility of remotely inferring the material properties of objects.
TL;DR: In this article, the effects of wind farms on radionavigation systems were evaluated using an electromagnetic CAD model from a real structural design, and the results were analyzed for several geometrical configurations of a three-bladed rotor and compared with the mast.
Abstract: The implementation of wind farms establishment in France is increasing. When wind farms are located close to radionavigation systems, it becomes important to evaluate their electromagnetic effects on existing radionavigation instalations. In this study, the radionavigation system is a VOR (VHF omnidirectional radio) operating at about 110 MHz. Because rotor blades are made of a balsa and dielectric multilayers composition, their electromagnetic behavior differs from that of metal blades at VHF frequences. In this study, we first obtain an electromagnetic CAD model from a real structural design; then we calculate the far field scattering matrix from an integral method (CESC code [1] method of moment) for a (30 m) dielectric blade and compare it with a metal one using RCS (radar cross section) calculation. The impact of (40 m long) dielectric blades is compared with the (65 m high) metal mast effect in terms of scattered field, and then the VOR error (bearing error) is evaluated. These results are analyzed for several geometrical configurations of a three-bladed rotor and compared with the mast. The study is extended on wind farms to discuss geometrical configuration effects with regard to a VOR location.
TL;DR: In this article, the authors investigated the electromagnetic scattering of two or more incident plane waves for a perfect electromagnetic conductor (PEMC) circular cylinder, coated with a metamaterial having negative index of refraction.
Abstract: —Electromagnetic scattering of two or more incident plane waves has been investigated for a perfect electromagnetic conductor (PEMC) circular cylinder, coated with a metamaterial having negative index of refraction. The incident waves are considered for both the TM and TE cases in the analysis. The scattered fields are calculated by the application of appropriate boundary conditions at the interfaces between the different media. It is assumed that both the PEMC cylinder and the coating layer are infinite along the cylinder axis. The numerical results are compared with the published literature, and are found to be in good agreement.
TL;DR: In this article, an effective numerical method for determining the scattered electromagnetic fields from thin wires is presented and discussed, which is modeled by the integral equations of the first kind, and illustrative computations are given for several cases.
Abstract: In this paper an effective numerical method for determining the scattered electromagnetic fields from thin wires is presented and discussed. This problem is modeled by the integral equations of the first kind. The basic mathematical concept is the method of moments. The problem of determining these scattered fields is treated in detail, and illustrative computations are given for several cases.
TL;DR: In this article, a new set of orthogonal basis functions is used to solve these integral equations via collocation method and numerical solutions of these equations are given for some cases of resistance distributions.
Abstract: In this paper the problem of electromagnetic scattering from the resistive surfaces is carefully surveyed. We model this problem by the integral equations of the second kind. A new set of orthogonal basis functions is used to solve these integral equations via collocation method. Numerical solutions of these equations are given for some cases of resistance distributions. Presented method in this paper can be easily generalized to apply to other cases.
TL;DR: In this article, a variational spacetime integrator for Maxwell's equations without sources is presented. But the integrator is not suitable for the case of free sources of charge and current.
Abstract: In recent years, two important techniques for geometric numerical discretization have been developed. In computational electromagnetics, spatial discretization has been improved by the use of mixed finite elements and discrete differential forms. Simultaneously, the dynamical systems and mechanics communities have developed structure-preserving time integrators, notably variational integrators that are constructed from a Lagrangian action principle. Here, we discuss how to combine these two frameworks to develop variational spacetime integrators for Maxwell's equations. Extending our previous work, which first introduced this variational
perspective for Maxwell's equations without sources, we also show here how to incorporate free sources of charge and current.
TL;DR: In this paper, a volume integral equation formulation for eddy-current non-destructive evaluation of ferromagnetic tubes affected by volumetric defects is proposed, based on the method of moments for both fictitious electric and magnetic currents within the defects.
Abstract: We propose a volume integral equation formulation for eddy-current nondestructive evaluation of ferromagnetic tubes affected by volumetric defects. We solve the system of integral equations (introduced into the model by application of Green's theorem) by the method of moments for both fictitious electric and magnetic currents within the defects, and calculate variations of impedance of the probes by the reciprocity theorem. We have made thorough comparisons of our results with finite-element-method simulations and with experimental data as well.
TL;DR: The characterization of conductive obstacles in subsoil is investigated in the induction regime, based on the extended Born approximation, the Lax-Foldy multiple diffraction theory, and introduction of equivalent spherical obstacles.
Abstract: The characterization of conductive obstacles in subsoil is investigated in the induction regime. Validated by numerical experimentation, a simple model is proposed to calculate the main electromagnetic quantities of interest, the interaction between the obstacles being taken into account. The model is based on the extended Born approximation, the Lax-Foldy multiple diffraction theory, and introduction of equivalent spherical obstacles. Those are retrieved via a hybrid algorithm of differential evolution using a communication strategy between groups, which in particular enables separation of coupled obstacles close to one another.