摘要:

Duality transformation, defined as a linear transformation between electromagnetic six-vectors, is known to transform electromagnetic problems in a linear (bi-anisotropic) medium to electromagnetic problems in another linear medium. This gives a possibility to create analytical expressions for the Green dyadic for media which are dual to simpler media with known Green dyadic solutions. Different forms of the duality transformation of fields are considered and their properties in terms of eigenfunctions are discussed. After this, corresponding transformations to medium parameters are considered in terms of their eigenmedia, i.e., media which are transformed in a simple manner. As a particular example a nonreciprocal anisotropic medium is considered, for which the Green dyadic was recently constructed in analytic form. It is shown that when the medium is transformed to a nonreciprocal bi-anisotropic medium, its Green dyadic can be obtained through the same transformation.

ISSN:0920-5071    

DOI:10.1163/156939398X00232

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In order to investigate the properties of three-dimensional metallic photonic crystals, we have developed an adaptation of Harrington's method for scattering by thin wires. Due to the peculiarity of photonic crystals, we have been led to renounce to two assumptions: the current intensity in the wires is not assumed to vanish at a free extremity of a wire and the Kirchhoff law at a junction between wires is not used any longer. It is shown that, paradoxically, the numerical implementation is simplified by these changes and that our method provides a better convergence of the results. Using our code, the properties of 3D metallic photonic crystals are investigated and compared with those of 2D crystals.

ISSN:0920-5071    

DOI:10.1163/156939398X00241

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This paper describes a new method for analyzing the high-frequency EM scattering from large open-ended cavities. Iterative solutions based on Physical Optics (PO), such as the Iterative Physical Optics (IPO) or the Progressive Physical Optics (PPO) method, have proved to be efficient techniques for computing the scattering of relatively shallow cavities. In order to improve the efficiency for deep cavities a segmented approach is proposed. In this technique the cavity is split into several sections and the magnetic field integral equation (MFIE) is solved independently for each of them, using either IPO or PPO to obtain their scattering matrices. The response of the whole cavity is found via a connection algorithm which leads to evaluate a generalized reciprocity integral over a surface close to the cavity end. This approach reduces drastically the computational cost with respect to both IPO and PPO methods, mainly for deep cavities. Some numerical results are compared with a modal reference solution to demonstrate the accuracy and efficiency of the new approach.

ISSN:0920-5071    

DOI:10.1163/156939398X00250

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A systematic study of parameter matrices (scattering, impedances and admittances) of symmetrical three-ports with isotropic and gyrotropic media is carried out. A new classification of the three-ports based on geometrical symmetry with regard to the time reversal operator is suggested. The approach uses the theory of magnetic point groups, the Curie principle and the concept of gyrotropic symmetry and gyrotropic antisymmetry. All the possible parameter matrices of the three-ports with one-mode waveguides are obtained. The correspondence of these matrices to magnetic point groups of symmetry is determined.

ISSN:0920-5071    

DOI:10.1163/156939398X00269

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This paper reports the implementation of a 2D-wavelet-based Galerkin method in the space-time domain, for the modeling of a 1D-structure's electromagnetic response to a pulsed excitation. The choice for the most suitable wavelet basis was guided by the analysis of the mathematical and physical peculiarities of the problem. First results exhibit that wavelets seem to be a great candidate for the solution of partial differential equations in the case of non-periodic sources.

ISSN:0920-5071    

DOI:10.1163/156939398X00278

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Based on the theory of distributions, this paper presents a simple derivation of the singularities and discontinuities associated with the eigenfunction expansions of the dyadic Green's functions for biisotropic media. The approach deals directly with Maxwell equations cast into dyadic forms prior to explicit determination of the dyadic Green's function formula. For both electric and magnetic dyadic Green's functions, the source point singularities are obtained without any integration and the discontinuities in their tangential and normal components across the source point are determined in compact forms directly from Maxwell dyadic equations. From the discontinuity relations, boundary conditions involving the tangential and normal components of electric and magnetic fields are derived. Due to the availability of different sets of constitutive relations characterizing a biisotropic medium, the singularities and discontinuities are discussed based on the commonly used Post-Jaggard and Drude-Born-Federov relations.

ISSN:0920-5071    

DOI:10.1163/156939398X00287

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This paper presents a novel analysis of the classical electromagnetic scattering from a conducting circular disk. A hybrid method which combines the vector wave eigenfunction expansion technique, the least squares method, the mode-matching method, and the dyadic Green's function is applied to derive the unknown scattering coefficients of the expanded eigenfunctions of scattered fields. Orthogonality of the vector wave functions is also utilized to simplify the problem. The edge effects of the thin conducting circular disk are considered in the formulation of the scattering coefficients. Although coupled to teach other, the scattering coefficients are obtained in a closed form and expressed in terms of compact matrices using the least-squares algorithm. Numerical computation of the radar cross sections (RCS's) of the perfectly conducting disk is carried out. Experimental data and theoretical results published elsewhere are also used to confirm the applicability of the hybrid method developed in this paper.

ISSN:0920-5071    

DOI:10.1163/156939398X00296

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

New analytical and numerical results concerning the location limit of the lowest natural frequencies and the corresponding normalized phase velocities are obtained for azimuthally-periodic two-dimensional cavity in the TE-case. The properties of the groove modes are investigated for both cases of the lowest and higher-order natural frequencies.

ISSN:0920-5071    

DOI:10.1163/156939398X00304

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Scattering of a transverse electric (TE) wavefield by an inhomogeneous lossy dielectric cylindrical obstacle embedded in a lossy dielectric half-space is investigated. The cylinder is of arbitrary cross-section, and its axis lies parallel to the interface. The formulation involves a domain integral equation of the field obtained by applying the Green's theorem to the appropriate Helmholtz wave equations. The convolution-correlation structure of the formulation is such that the discretized counterpart of the integral equation (provided by the application of a Method of Moments where the obstacle is divided into triangular patches and where the contrast and the H-field are expanded using two different basis functions) can be efficiently handled using a FFT-based conjugate gradient solver. The validity of the approach is illustrated by comparison with results found in the literature.

ISSN:0920-5071    

DOI:10.1163/156939398X00313

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Concept of shifted frequency internal equivalence (SFIE) for electromagnetic scattering problems involving homogeneous or inhomogeneous bodies is explained and applied to multi-frequency electromagnetic scattering from inhomogeneous dielectric and/or magnetic rectangular waveguides. As is well known, surface integral formulation is only applicable to homogeneous structures, and in volume integral formulation it is necessary to repeat the solution process by generating data at each incident field frequency.Here, it is shown that, volume interaction part of the data generated only at a single frequency may be utilized at other frequencies in a wide frequency band while applying SFIE. Upon combination with an external equivalence, the solution is readily obtained.

ISSN:0920-5071    

DOI:10.1163/156939398X00322

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor