摘要:

A simple analytical solution is given for a current point source in the vicinity of a thin metallic sheet conductor - which may have polarizable surfaces. The solution is obtained as the limit of a general layered model for a thin intermediate stratum having high conductivity while the thin coating strata have high (complex) resistivities. It is shown that the resulting composite thin sheet can also be treated at the outset employing effective boundary conditions which relate the jump or discontinuity in the tangential electric fields to the normal current flow on the two sides of the sheet. The appropriate discontinuity of the potential is also incorporated into the effective boundary conditions.

ISSN:0920-5071    

DOI:10.1163/156939394X00272

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Several dielectric models have been previously proposed to explain the permittivity of mixtures from the known dielectric constant and volume fractions of the constituents. The materials may be lossy and this leads to a complex effective permittivity for the mixture where the imaginary part stands for the absorption losses of the mixture. However, the scattering losses are not incorporated in the effective permittivity. The result is therefore confined to a low-frequency limit. In this paper an attempt is made to incorporate the scattering losses in the effective permittivity of the medium consisting of the discrete scatterers immersed in a host material. The inclusions are assumed to be spherical. The results are applicable to general multiphase mixtures, and the scattering spheres of the different phases may have size distribution. The results are applied to calculating the complex effective permittivity of wet snow. The prediction of the model seems to agree with the experimental data if the scattering losses and the distribution of liquid water in the pore space have been taken into account.

ISSN:0920-5071    

DOI:10.1163/156939394X00281

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The electromagnetic scattering from arbitrarily shaped 3-D cavities with coated walls is presented. In this formulation, the cavity is divided into smaller sections. Each section is individually analyzed with a boundary integral equation, followed by the standard moment method procedure to arrive at an admittance matrix for each section. These admittance matrices for different sections are then cascaded using a connection scheme based on microwave network theory. Once the admittance matrix of the whole cavity is obtained, the electric field on the aperture and thus the backscattered field can be obtained by the generalized network formulation. Triangular patch basis functions are used to provide easy mesh generation using standard CAD tools. To model wall treatment, the impedance boundary condition is applied. The numerical results generated by the present approach show good agreement with the modal solutions for regular geometries. An example for a cavity with coated walls is also presented.

ISSN:0920-5071    

DOI:10.1163/156939394X00290

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In this paper, we propose a new approach concerning the existence and propagation of matter and radiation in vacuum. By considering the possible existence of scalar inhomogeneous standing waves in vacuum, we were able to derive Maxwell's equations and Lorentz force laws from first principles.

ISSN:0920-5071    

DOI:10.1163/156939394X00308

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Electromagnetic plane wave scattering by a partially filled trough on the ground has been analyzed by high frequency asymptotic techniques based on Geometrical Theory of Diffraction. Field in the trough region has been formulated in terms of parallel plane waveguide modes, whose excitation (coupling) coefficients are obtained by ray-mode conversion techniques. Previous investigation for obtaining such excitation coefficients has now been extended to account for multiple edge interaction effects. Numerical calculation has been done extensively and thus obtained results are then compared with those by other methods. Good agreements have been observed except for grazing incidence case. It is found that first and secondary modal re-radiation fields from the indented trough region play an important role for scattering far field, and primary edge diffracted field contributes mainly to reflection boundary direction. It is also found that the formulation with these higher order interaction terms can be used even for narrow aperture cases, as well as shallow cases.

ISSN:0920-5071    

DOI:10.1163/156939394X00317

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

At each application of the recursive process presented below, a set of problems is solved sequentially. A typical problem at each stage of the process comprises an aperture of a certain width in a conducting cylinder. Its solution is constructed from the data available at this stage, viz. the solution for the preceding problem and an additional aperture cut into the conductor. This process complements the add-on patch formulation reported in the recent past, and it retains its useful features. Prior to commencing the process, the short circuited conductor is efficiently analyzed with pulse shaped incident electric fields. The "short circuited" current obtained in this pre-processing stage is used to generate building blocks for the subsequent recursive process. From this point on, only the electric field quantities are used for representing both the exciting and the unknown functions. This representation leads to a purely algebraic algorithm, which requires no integral operators and hence is quite efficient. This method is most suitable for large conductors with smaller aperture, and for cases where the large short circuited conductors are easily computable.

ISSN:0920-5071    

DOI:10.1163/156939394X00326

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The general approach to the accurate calculation of the two-dimensional electromagnetic field scattered by a system of infinitely thin and extended perfectly conducting screens in a dielectric slab (waveguide) is suggested. The slab is situated between two semi-infinite homogeneous half-spaces of different electromagnetic properties and is illuminated by two-dimensional E - or H - polarized electromagnetic waves. The cross-section of the screens system is supposed to be arbitrary. The integral equations of the corresponding diffraction problem are derived and the numerical method of solving them is developed. The integral equations kernel contain the usual free-space Green function and the Sommerfeld-type integrals of two variables. The efficient method of the second kernel part evaluation is proposed. Some field calculation results for screens of rectilinear and elliptic cross-section are presented and discussed.

ISSN:0920-5071    

DOI:10.1163/156939394X00335

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Classical solutions to the charged conducting closed cylinder are external transformations of the closed boundary to a circle, or the real axis of another plane. By making use of some symmetries, if any, of the field, we can change this external into an internal problem by the Schwartz-Christoffel transformation, resulting in easier and better solutions.

ISSN:0920-5071    

DOI:10.1163/156939394X00344

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A method devised by Arnaud to evaluate the transverse coupling between dielectric waveguides has been successfully applied with a step-like approximation to two skew rectangular dielectric waveguides lying in different parallel layers, and tractable analytical expressions, which can be very useful in the analysis and the design of the waveguides, have been obtained. The mode power along one of the guides when the other is excited has been calculated and the results compared with experimental results appearing in the literature. The agreement is in general quite satisfactory.

ISSN:0920-5071    

DOI:10.1163/156939394X00353

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A new, reduced-unknown integral equation for scattering by an inhomogeneous dielectric/magnetic structure is discretized using rectangular brick elements. The new integral equation involves only the electric field (3 scalar components) as the unknown quantity whereas traditional formulations employed both electric and magnetic fields for a total of 6 scalar components per cell. Edge-based linear shape functions are used for the expansion of the field inside the dielectric and a modified Galerkin's technique is employed for testing the integral equation. Results demonstrating the validity of the integral equation are presented.

ISSN:0920-5071    

DOI:10.1163/156939394X00362

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor