摘要:

Thenatural frequencies of a hollow, perfectly conducting sphere with a circular aperture are calculated. The trajectories of the poles in the complex plane reveal an intriguing behavior which depends on whether the poles originate from internal or external sphere resonances. It is found that the modal degeneracy of the complete sphere is removed by the addition of the aperture.

ISSN:0920-5071    

DOI:10.1163/156939399X01302

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

In this paper a one-dimensional inverse scattering problem is considered. An approximate inversion formula in a closed-form is derived. Using this formula, an approximate permittivity profile is generated from the partial knowledge of the frequency domain reflection coefficient. This formula is deduced through the application of a linear transformation to a nonlinear differential equation for the frequency domain reflection coefficient. Examples are given to demonstrate the accuracy of this approximate inversion formula.

ISSN:0920-5071    

DOI:10.1163/156939399X01311

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Transmission characteristics of a folded waveguide structure, which consists a bifurcating metal plate with finite thickness between the lower and the upper metal plate guides and being placed unsymmetrically in the cross-sectional plane in general, are investigated theoretically by using mode matching technique for the application as a feeder for any planar radiating structure. A novel technique is proposed in which the inclusion of step junctions in the folded waveguide portion play an essential role in minimizing reflections caused by the presence of finite thickness of the bifurcating metal plate as well as the unsymmetry in the folded portion and hence, a complete power transmission could be achieved. Based on the numerical computations some practical structures which could be applied as feeders for plasma generating devices are designed and the perfect matching performances are demonstrated.

ISSN:0920-5071    

DOI:10.1163/156939399X01320

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The design of high-order, finite-difference, time-domain numerical solvers for Maxwell's equations is presented herein. Particularly, high-order spatial discrete operators are designed using Fourier techniques in κ-space; the desired accuracy order is verified both analytically and numerically. As an example of the power of the method, an eighth-order super compact operator is designed on a three-point stencil. To advance the equations the fourth-order Runge-Kutta integrator is employed. The schemes are quantified in terms of their dispersion and dissipation error characteristics and the corresponding Courant number is established using standard Fourier analysis. Case studies involving a one-dimensional cavity and the rectangular waveguide are presented. For these case studies, specific boundary operators are introduced, and the time-stability of each scheme is cataloged. Moreover, the data associated with these case studies demonstrate the key features of the numerical schemes: The low accumulation of phase and dissipation type errors.

ISSN:0920-5071    

DOI:10.1163/156939399X01339

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

We have studied the electromagnetic wave scattering at second harmonics from the system of two scatterers (dipoles or loop) containing a nonlinear local load in the form of a semiconductor diode. The scatterers were placed in a free space. We have considered the following geometrical configuration of the scatterers: dipoles disposed in mutually orthogonal planes, parallel dipoles, parallel scatterers (loops or dipoles) in the case when only one of them has a diode. In all cases the main attention is paid to study the behavior of the backscattering field at the double frequency on the distance between half-wave scatterers and location of the load in them.

ISSN:0920-5071    

DOI:10.1163/156939399X01348

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A rigorous and efficient method for characterizing E-/H-plane multiport junctions in rectangular waveguides is presented by using the mode-matching method combined with Fourier transform technique. The method is based on a field-theoretical full-wave approach. The electric and magnetic fields of a main waveguide in the junction are expressed in terms of Fourier integrals and matched in the Fourier transformed domain to the aperture fields expanded by the normal modes in each of arm waveguides. This yields a set of linear equations in analytically closed form to calculate the scattering parameters of the multiport systems. The numerical examples for a Magic-T junction and an asymmetric E-/H-plane three-port junction verify the accuracy and usefulness of the present method.

ISSN:0920-5071    

DOI:10.1163/156939399X01357

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A hybrid approach, combining the finite element method (FEM), boundary element method (BEM) and wavelet transform method (WTM), called FEM/BEM/WTM, is proposed for efficient solution of scattering from cylindrical scatterers of arbitrary cross sections. The hybrid technique uses the FEM to formulate the fields within a chosen fictitious boundary enclosing the considered scatterers and establish a relationship with those on the fictitious boundary. The fields outside the fictitious boundary are formulated by the integral equation method involving an integral expression of the fields over the fictitious boundary. Two fast-solving ways based on the WTM are presented. The use of the proposed hybrid technique always results in sparse moment matrices which can be efficiently solved by a sparse solver. Uniting the advantages of the FEM, BEM and WTM, the hybrid technique is able to effectively handle large-size unbounded problems in which arbitrary complex inhomogeneities are involved. Numerical results are given to demonstrate the merits of the hybrid technique.

ISSN:0920-5071    

DOI:10.1163/156939399X01366

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

In this paper, a hybridization method of moment (MOM) and equivalent edge currents (EECs) is presented to study the electromagnetic (EM) scattering from the slot antennas fed by the waveguides with arbitrary termination. The EECs is applied to calculate the EM scattering of a conducting plane, including the diffraction of edge, while the MOM is used to obtain the fields in the slots and deal with the coupling between them In conjunction with them, the EM scattering of the slot antennas can be evaluated quickly. Several results are presented, demonstrating the applicability of this technique.

ISSN:0920-5071    

DOI:10.1163/156939399X01375

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A generalized fractional order integral operator is derived that relates the one and two dimensional Green's function for a geometry with parallel plane interfaces. It is found that order of the operator is independent of the geometry while lower limit and operational variable are functions of the geometry. Utilizing the general fractional order operator, it is possible to calculate the fractional solutions for Helmholtz's equation in a geometry with parallel plane interfaces. A generalized expression is proposed for far-zone fractional solution in a geometry with parallel plane interfaces.

ISSN:0920-5071    

DOI:10.1163/156939399X01384

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The potential applications of electromagnetic (EM) chirality, together with the fact that a general ellipsoid shape can simulate a variety of common objects, such as discs, needles etc., constitute the motivation of the present work. Scattering of EM waves incident on an ellipsoidal object of chiral property is analyzed using Fourier analysis, in conjunction with an integral equation technique. The inner field of the scatterer is described in terms of superposition of plane waves satisfying the vector Helmholtz wave equation inside the chiral media and a Galerkin procedure is employed to solve a volume integral equation obtained by applying the Green's theorem. A highly stable numerical code is obtained, which is verified by comparison with previously published solutions. Numerical computations have been carried out for various scatterers and interesting scattering properties of waves from chiral media are observed. Especially for a linearly polarized plane wave incidence, the subsequent change of its polarization is investigated and discussed.

ISSN:0920-5071    

DOI:10.1163/156939399X01393

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor