摘要:

A closed-form expression is derived for the integration over a triangle of the normal component of electric flux from a dipole in a homogeneous space, weighted by a linear basis function. This integral arises in the finite element solution of the three-dimensional Poisson equation with a dipole source when solving for the "subtracted potential," i.e., the total potential minus the potential of the dipole in an infinite homogeneous medium. This closed-form integral evaluation allows for an efficient finite element solution for the subtracted potential that is more accurate than can be achieved using a direct finite element solution for the total potential, since the subtracted potential is a smoother function with no singularity. The formulation begins by first deriving a formula for the electric flux through a triangle due to a dipole source in a homogeneous medium (no basis function weighting). This formulation is based on an identity that is derived, which equates the electric flux from a dipole source through an arbitrary surface to a contour integral of the electric field of a point (monopole) source along the boundary of the surface. This identity results in a simple closed-form expression for the electric flux of a dipole through a triangular surface. As an extension of this result, a closed-form expression is then derived for the more complicated case where the dipolar flux density through the triangular surface is weighted by a linear basis function. Compared to numerical integration, the closed-form expression is more computationally efficient and main tains accuracy regardless of how close the dipole gets to the surface.

ISSN:0272-6343    

DOI:10.1080/027263400308230

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

A rigorous mode-matching technique is implemented for the study of the unloaded Q factor of a dielectric resonator operating in the TE01delta, TM01delta, and HEM11deltamodes. The cylindrical dielectric resonator is loaded into a metal enclosure and placed on a dielectric substrate. The analysis permits the calculation of the loss introduced by the resonator parameters and also the electromagnetic energy distribution inside the cavity. Numerical results are presented demonstrating the variation of the unloaded Q factor, electromagnetic energy distribution, and power loss against geometrical and material parameters. Finally, the accuracy of the calculations is verified with comparison with another rigorous method.

ISSN:0272-6343    

DOI:10.1080/027263400308249

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

Predictions for scattering from randomly very rough surfaces are developed and compared with experimental data. The integral equation method with multiple scattering is developed to predict this backscattering enhancement phenomenon. The backscattering enhancement can be predicted from the constructive interference of multiple surfaces scattering from a very roughly random surface. For specialized surfaces involving roughness large compared with the incident wavelength, the backscattering enhancement takes place. In this paper we show that the phenomenon of backscattering enhancement becomes evident for both the normalized surface height > 1.5 and the surface root mean square slope > 0.5. Further, we also show that the incident angle is a factor for the backscattering enhancement. The derivation of the basic surface scattering model is provided and a computer simulation is also provided to compare with measurement. The phenomenon of backscattering enhancement is observed in both the integral equation model (IEM) model prediction and experimental data. In comparing the IEM model with measured data over a wide range of frequency and angle, excellent agreement is found. The difference between the model prediction and data is less than a dB.

ISSN:0272-6343    

DOI:10.1080/027263400308258

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

The electromagnetic continuity condition is extended from the classical condition on an interface between two media to a more general one relating sources and fields in a region between two regions of arbitrary media. The condition allows one to extend the classical Huygens principle to involve equivalent sources in a spatial region volume or on multiple surfaces. As an example, the generalized Huygens principle is applied to the formulation of a scattering problem in terms of a surface integral equation. Also, the transparent absorbing boundary (TAB) condition can be interpreted in terms of the extended Huygens principle.

ISSN:0272-6343    

DOI:10.1080/027263400308267

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

Typical limitations of integrated antennas such as bidirectional radiation, power loss via substrate modes, and broad radiation patterns can be corrected using a substrate lens. In this paper, various slot-fed substrate lens antenna (SLA) configurations are examined, and a novel hybrid physical optics analysis technique, suitable for electrically small geometries, is presented. Based on this method, directivity and reflection loss calculations for elliptical and hyperhemispherical synthesized lenses are carried out. It is found that the conditions for maximum directivity and minimum reflection loss do not coincide, and thus certain performance compromises are necessary. The results are confirmed experimentally.

ISSN:0272-6343    

DOI:10.1080/027263400308276

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

The characteristic-based finite-volume time-domain method is applied to analyze the scattering from conducting objects coated with lossy dielectric materials. Based on the characteristic-based finite-volume scheme, two numerical strategies are developed to model the electromagnetic propagation across different dielectric media. One introduces a connecting boundary to separate the total-field region from the scattered-field region. The other employs the scattered field formulation throughout the computational domain. These two strategies are verified by numerical experiments to be basically equivalent. A numerical procedure compatible with the finite-volume scheme is developed to guarantee the continuity of the tangential electric and magnetic fields at the dielectric interface. Rigorous boundary conditions for all the field components are formulated on the surface of the perfect electric conducting (PEC) objects. The numerical accuracy of the proposed technique has been validated by comparison with theoretical results.

ISSN:0272-6343    

DOI:10.1080/027263400308285

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor