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The theory of characteristic modes (TCM) is presented for arbitrarily shaped 3-D structures including perfect electric conductors (PECs) and homogeneous penetrable objects. It is shown that by properly expressing the weighting operator of the generalized eigenvalue equation in terms of the integral operators related to the radiated fields, TCM can be formulated directly for the surface integral equation formulation of the problem. This avoids symmetrization or other modifications of the equations. The eigenvalues are shown to be related to radiated, reactive, and dissipated power, and the corresponding far-field patterns are orthogonal. The previously introduced TCM formulations for PEC are special cases of this generalized TCM.

The antenna proposed is a new geomantic structure of Ultra-Wideband (UWB) Anti- Podal Vivaldi antenna (AVA). It remarkably offers an attractive performance over the bands of cellular networks. However, its benefits are not limited only in particular applications, whereas radar imaging, mining detection, the biomedical science in the heating of brain cancer tumor and treatment, and the wireless communication are considered as the main applications suitable for utilization. Therefore, the focus on this paper is to spot the light illuminating into the cellular communications network Systems. On the other hands, several characteristics of Vivaldi antenna have been provided such as the gain, return loss, Voltage Standing Wave Ratio (VSWR), current distribution and E- fields. Finally, the results illustrate the capability and feasibility of the designed antenna.

Resonances, i.e., extrema of the eigenvalues of characteristic modes for closed perfectly conducting objects are investigated. The characteristic modal solutions based on the electric, magnetic, and combined field integral operators (EFIO, MFIO, and CFIO) are studied and compared with analytical solutions for a sphere. All these formulations are found to capture both external (radiating) and internal (cavity) resonances predicted by the analytical expressions. At the internal resonances, the eigenvalues obtained with the EFIO- and MFIO-based approaches are not correct, and the corresponding modes are nonunique. These solutions also exhibit a strong duality between the electric (TM) and magnetic (TE) type modes. A connection is found between the external and internal resonances and the condition numbers of the matrices. The modal expansion of the CFIO-based solution is correct, even though it also experiences the nonuniqueness of the EFIO- and MFIO-based solutions.

©2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. The discretization by the Method of Moments (MoM) of electromagnetic integral equations, namely, the Electric Field Integral Equation (EFIE) for perfect electric conductors (PECs) and the Poggio-Miller-Chan-Harrington-Wu-Tsai (PMCHWT) integral formulation for penetrable objects, is usually carried out with divergence-conforming sets of basis functions. However, in the single-surface analysis of piecewise homogeneous composite objects the implementation of divergence-conforming sets around junction-edges, where several regions intersect, becomes convoluted. Recently, the monopolar-RWG discretization, discontinuous at edges, of the EFIE and the PMCHWT formulation has been proposed. In this paper we show how this facet-based scheme becomes well suited for the single-surface analysis of piecewise homogeneous composite objects without giving special attention to junction-edges.

A full-wave analytical method using the addition theorems and Hertzian potential functions are used to compute the radar cross section of a sphere coated by several layers composed of common materials and metamaterials. The minimization and maximization of radar cross section of a perfectly electric conductor sphere with such coatings are realized in a frequency band-width and in a wide interval of angles. One of the novelities of this contribution is, taking into dispersion relations of physically realizable metamaterials. So that the optimization procedure for RCS reduction is applied due to the coefficients describing dispersion characteristics. The method of least square is used for the design of a class of radar absorbing materials. The minimization of the error functions are performed by the combination of genetic algorithm and conjugate gradient method. It is shown that the proposed method of computation of radar cross section and its extremization effectively leads to the design of dispersive and isotropic metamaterials for the realization of radar absorbing materials.

International audience; This paper presents Exponential Tapered slot antenna (ETSA) radiation pattern measurement in Non Anechoic Environment. It suggests a method based on CMC decomposition and modal filtering in order to get rid of perturbations. First Cylindrical Near-field to Far-field Transformation and calculation of CMC are described. Then a simulation on an ETSA and a Perfect Electric Conductor (PEC) obstacle is done. Simulation results are presented for a frequency of 2 GHz. Far-field pattern cut at theta=90° is presented. Comparison between the simulated radiation pattern of ETSA without obstacle and the one of ETSA with PEC after filtering is proposed. A good agreement between these two curves is observed.

Magnetic induction tomography (MIT) is an imaging technique based on the measurement of the magnetic field perturbation due to eddy currents induced in conducting objects exposed to an external magnetic excitation field. In MIT, current-carrying coils are used to induce eddy currents in the object and the induced voltages are sensed with the receiving coils. When the driving frequency is significantly high relative to the frequency range in which MIT normally operates, metallic targets with high conductivity between the coils can be treated as perfect electric conductors (PEC) with negligible errors. In this scenario, the penetration depth of the magnetic field into the target is extremely small and the traditional versions of the finite element method (FEM) are not efficient for the calculation of the sensitivity and the forward problem due to the requirement for large number of elements to reach an acceptable computational precision. Other versions of FEMs (such as Hp-FEM), which have higher discretization efficiency and more advanced elements to satisfy the requirement, are exceptions. Nevertheless, the discretization regions for all FEMs have to extend beyond the region that contains the conducting object and volumetric elements are generally required for 3D problems. In contrast, the boundary element method (BEM) based on integral formulations becomes an effective way to analyze this kind of scattering problem since meshes are only required on the surface of the object. By point collocation, the boundary integral equations can be transformed into linear equations. Numerical methods are used to solve the linear equations and the solution of the original integral equations can be obtained. In this paper, we compute four typical sensitivity maps between the coil pairs in high-frequency MIT system due to a PEC perturbation. The magnetic scalar potential is used to improve the efficiency. Five PEC objects of different shapes are used in the simulation. The results have been compared with the experimental results and that obtained from the H·H formulations. We can know that the sensitivity maps derived by BEM are in good agreement with that from the experiment and theoretical solution. Overall, BEM is an effective way to calculate the sensitivity distributions of a high-frequency MIT system. © 2013 IOP Publishing Ltd.

Magnetic induction tomography (MIT) is an imaging technique based on the measurement of the magnetic field perturbation due to eddy currents induced in conducting objects exposed to an external magnetic excitation field. In MIT, current-carrying coils are used to induce eddy currents in the object and the induced voltages are sensed with receiving coils. When the driving frequency is significantly high, metallic targets with high conductivity between the coils can be treated as perfect electric conductors (PEC) with negligible errors. Boundary Element Method (BEM) based on integral formulations becomes an effective way to analyze this kind of scattering problems since meshes are only required on the surface of the object. But how to deal with the singular integral, which is a heavy burden for the computation, is a difficult issue unlikely to avoid. The method of auxiliary source (MAS) introduces the concepts of auxiliary surface and auxiliary source which avoid the computation of singular integrals. In contrast to the BEM, the MAS is more simple and fast for solving the PEC scattering problem in high MIT system. In this paper, the formula of sensitivity distribution was obtained by MAS with high efficiency and accuracy and then simulations by MATLAB were programmed. According to the good agreement of these results obtained by different numerical methods, we can know that MAS is an effective way to analyze the sensitivity distributions of high frequency MIT system. ?? 2013 IEEE. cited By (since 1996)0; Conference of org.apache.xalan.xsltc.dom.DOMAdapter@1ce0bdd5 ; Conference Date: org.apache.xalan.xsltc.dom.DOMAdapter@66cef9c2 Through org.apache.xalan.xsltc.dom.DOMAdapter@1e6f6449; Conference Code:98450

Electromagnetic scattering from an infinite and a finite length PEMC circular cylinder, illuminated by an arbitrarily oriented dipole, is investigated theoretically. An electric dipole as a source of excitation is considered first, and then a magnetic dipole as a source of excitation is treated. In contrast to the case of an axially directed dipole, it is shown that no additional terms are needed to incorporate the cross-polarized component of the field for the case of radial and circumferential dipoles. Numerical verifications are presented to verify the validity of derived results and numerical code by comparing results with the published literature.

International audience; The use of artificial magnetic conductor (AMC) has proved to be very effective to simultaneously enhance the gain and reduce the thickness of planar antennas. Due to the strong resonant nature of such metamaterials, low profile antennas based on periodic AMC exhibit poor performances in term of bandwidth. The purpose of this study is to use a non intuitive and automatic CAD tool to synthesize an ultra compact planar antenna operating in a wide frequency band. The proposed structure is a Fabry Perrot based cavity antenna made of a partially reflected surface (PRS) above a perfect electric conductor (PEC) including a patch antenna source. The PRS consists in a AMC formed by a dielectric slab with periodically located conducting elements printed on each faces. The aim is to optimize the shape of the basic cell of the periodic PRS-AMC in order to reduce by a factor 5 the thickness of the cavity (λ/10) while allowing a wide frequency band operation (40%). The process of optimization is carried out using a micro genetic algorithm coupled to a "home made" 3D-TLM electromagnetic software implemented on a parallel IBM-SP3 computer[2].