摘要:

A fast yet accurate method for analyzing a wire antenna of arbitrary shape is developed. In addition to the straight line in a wire grid model, a new canonical element, namely, an arc of constant radius of curvature is introduced. For a curvilinear antenna, combination of bent and unbent lines could substantially reduce the fitting error. A technique is devised that solves the vector wave equation on the surface of an arced segment as simple as if it were a straight one. As each segment is relatively long in the enhanced mode, symmetry of the impedance matrix can be fully utilized to speed up the computation. The scheme is used to study some typical curvilinear antennas and excellent results are observed.

ISSN:0920-5071    

DOI:10.1163/156939395X00613

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper presents an extension to a hybrid finite element boundary integral method. This method can be used to compute the scattering from 3D inhomogeneous bodies of any shape with anisotropic characteristics. The modeling of thin layers between materials by an asymptotic jump sheet impedance condition has been added to the formulation. The mathematical formulation is based upon local differential equations for the modeling of the objects. The integral equations account for the propagation in the unbounded surrounding medium and provide an exact boundary condition. A lot of results have been published on conducting or coated objects. The aim of this paper is to show that hybrid methods can model more complex objects. Results for 3D objects made of several materials, including anisotropic material or thin layers are presented.

ISSN:0920-5071    

DOI:10.1163/156939395X00622

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Notation using six-vectors and six-dyadics appears very applicable for describing electromagnetic problems in general bi-anisotropic media, because with normal three-vector notation analytic expressions often tend to be very complicated. Introducing some operations, recourse to the three-vector and three-dyadic notation during the analysis can be avoided. A number of theorems and concepts of electromagnetic fields in bi-anisotropic media are given as examples.

ISSN:0920-5071    

DOI:10.1163/156939395X00631

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The problem of the electromagnetic field generation by a magnetic dipole source on the surface of a perfectly conducting body is studied by using the boundary layer method. The field is first computed in the vicinity of the source, then matched with the creeping rays. The launching coefficients of these rays are computed up to the second order term, showing the effect of the difference of the principal curvatures of the surface.

ISSN:0920-5071    

DOI:10.1163/156939395X00640

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper deals with the study of wave propagation and scattering in a half-space random medium with a random interface. The surface randomness and the volume randomness are treated with equal importance and a multiple scattering solution is sought. The random fluctuations of both the random medium and the surface are assumed to be small and obey Gaussian statistics. These assumptions enable us to use approximations and physically identify the various scattering processes. The Feynman diagram technique is used to derive the Dyson equation and the Bethe-Salpeter (B-S) equation for the first and second moments of Green's functions, respectively. Two approximations, viz., the bilocal approximation and the nonlinear approximation are applied to the Dyson equation. Proceeding along similar lines the ladder approximation is applied to the B-S equation. The Feynman diagram technique affords us to clearly identify the scattering interaction between the random surface and the random medium. These interactions which are usually ignored in a single scattering approximation become important in a multiple scattering solution.

ISSN:0920-5071    

DOI:10.1163/156939395X00659

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

In this paper, a general model for voltage and currents induced by the primary and secondary field couplings in a multiconductor cable system buried in lossy earth, and illuminated by an external electromagnetic field is presented. Generalized form of equivalent transmission line equations (ETLEs) obtained from this model are presented, which could analyze many of the associated problems, involving the field couplings in underground transmission systems. These equations are then used to derive general solutions for the currents and potentials induced by the external fields along the underground conductors.

ISSN:0920-5071    

DOI:10.1163/156939395X00668

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

One can find various mesh truncation techniques in the literature for the finite element solution of electromagnetic scattering problems. In this paper, a mesh truncation approach referred to as the three-dimensional bymoment method is considered. This approach uses two z-directed Hertz vector potentials instead of three Cartesian field components to formulate the relevant boundary conditions. The pertaining FEM field solutions are calculated by treating the scattering problem as an interior region problem. The FEM field solutions are then numerically "coupled" on a second boundary surface that is conformal to the first one and completely enclosed by it. The "coupling" procedure yields a set of expansion coefficients, with the help of which the total field solution is written as an appropriate linear combination of the interior region FEM field solutions.

ISSN:0920-5071    

DOI:10.1163/156939395X00677

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A theoretical and numerical analysis of Liao's absorbing boundary condition (ABC) is presented. The form of the ABC is related to both space-time polynomial extrapolation and a one-way wave equation. A modification allowing the optimization of the ABC for specific angles of incidence or wave speeds is discussed. The stability of the ABC is also discussed, and a technique is presented for enhancing stability. Numerical results are presented to demonstrate the stability and accuracy of the ABC.

ISSN:0920-5071    

DOI:10.1163/156939395X00686

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A generalized Maxwell Garnett model for artificial composites formed of small bianisotropic particles arranged in three-dimensional arrays is developed. Explicit expressions for averaged dyadic constitutive parameters are given. The approach is suitable for the case of incomplete magnetoelectric coupling dyadics, since it leads to expressions which do not involve any inverses of these dyadics. Based on an analytical antenna model of single chiral particles, the averaged parameters can be easily evaluated. The theory is illustrated by numerical examples for uniaxial chiral structures. Reflection coefficients from an ideal conductor covered by uniaxial chiral slabs are calculated for different types of axially symmetric distributions of the inclusions. It is demonstrated that for different frequency ranges different geometries correspond to better reduction of reflection.

ISSN:0920-5071    

DOI:10.1163/156939395X00695

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The generalized spectral domain-exponential matrix technique (GSD-EMT) is used to investigate the radiation characteristics of a dipole antenna placed on various grounded Faraday chiral substrates, and such Faraday chiral materials include chiroferrite and semiconductor chiroplasma. Numerical results are presented to demonstrate the combined effects of gyrotropy and chirality on the pattern sharp as well as the main beam direction of dipole antenna, and the influences of different constitutive parameters are taken into consideration carefully. It is believed that the present study provide us much insight into the physical properties of Faraday chiral substrates.

ISSN:0920-5071    

DOI:10.1163/156939395X00703

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor