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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.

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.

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.