摘要:

The analysis for the electromagnetic radiation or scattering from a material cylinder in the presence of a wedge with impedance faces is presented. The problem considered is two dimensional where the incident field is polarized TM or TE to the axis of the wedge, and the material body may be of arbitrary shape and inhomogeneous. An integral equation is formulated where the field inside the material cylinder is the unknown quantity to be determined and the Green's function for the impedance wedge is included in the kernel of the integral equation which accounts for the presence of the wedge. The integral equation is then solved using a method of moments technique. Employing the specialized Green's function for the impedance wedge reduces the number of unknowns in the moment method matrix since unknowns are only required over the region of the material cylinder and not along the boundaries of the wedge. The primary application for this analysis is to study methods for reducing the EM scattering from wedge shaped objects; specifically the fields which diffract from the sharp corner formed by the edge of the wedge. Attaching a lossy material body to the tip of the wedge is an effective method for reducing these diffracted fields. Optimization techniques are also employed to design the loss profiles of the material bodies in order to maximize their performance for scattering reduction.

ISSN:0920-5071    

DOI:10.1163/156939396X00306

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Exact Image Theory, previously introduced to electromagnetic field problems involving arbitrary sources and planar interfaces of simple isotropic media, is extended to vertical electric and/or magnetic sources above a planar interface of a chiral medium with small chirality. The resulting image functions are shown to be generalizations of those encountered in the simple isotropic case and coincide with previously obtained quasistatic results. Far-field approximation of the image method is shown to lead to a simple reflection coefficient image principle.

ISSN:0920-5071    

DOI:10.1163/156939396X00315

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This communication presents an efficient technique for self-term evaluation of the uniform current vector potential integrals which often arise in certain cylindrical wire method of moments formulations. Simple approximating functions, derived from the application of numerical interpolation routines, are introduced that may be used in place of other more complicated techniques for evaluation of these integrals. In particular, this communication will focus on the development of these approximating functions for application in the moderately thick wire regime, where the reduced kernel approximation associated with thinner wires is no longer valid. It is shown that these proposed functions offer reasonably good accuracy over a wide range of wire segment lengths and radii.

ISSN:0920-5071    

DOI:10.1163/156939396X00324

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This paper presents the axial ratio beamwidth results obtained by different sequentially rotated microstrip patch antenna sub-array configurations. Simplified formulae of electrical radiation pattern allow a direct polarization estimation. To validate these formulae, a comparison with a rigorous calculation code using the Finite Difference Time Domain method (F.D.T.D.), through same cases simulated, gives good agreement. Finally, excitation errors introduced in simple analytical expressions are taken into account for two particular sub-arrays.

ISSN:0920-5071    

DOI:10.1163/156939396X00333

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The impulse characteristic calculation method for transient diffraction problem on the smooth convex ideally conducting object in the bistatic case is developed. The physical optics approach, which is modified by means of the exception of the "terminator breaks" provoked by the inadequacy of the surface current description near the "light-shadow" boundary, is used. Calculated formulae and bistatic impulse characteristic numerical calculation results for the ideally conducting triaxial ellipsoid are given.

ISSN:0920-5071    

DOI:10.1163/156939396X00342

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A Coupled-Integral-Equations Technique (CIET) for the analysis of multiple discontinuities and bifurcations in rectangular waveguides is presented. A set of coupled integral equations for the tangential electric field over the planes of the discontinuities are derived and then solved by the moment method. Basis functions, which include the edge conditions and mirror images in the walls of the waveguide, are used to accelerate convergence of the numerical solution. One or two basis functions are sufficient to accurately determine the reflection and transmission properties of H-plane discontinuities and bifurcations. Reflection and transmission properties of N discontinuities are computed accurately from a single matrix of the order of 3N x 3N instead of cascading the individual generalized scattering matrices whose dimensions increase rapidly as the distances between the discontinuities decrease.

ISSN:0920-5071    

DOI:10.1163/156939396X00351

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Static external fields are needed in physical and engineering problems, so that we discuss what fields can be generated by the involute of circle and by evolute of ellipse as well as by the evolute of evolute of ellipse. These curves have been in existence for a very long time and yet are not very well utilized in the electromagnetic area.

ISSN:0920-5071    

DOI:10.1163/156939396X00360

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A previous analysis for a horizontal loop antenna is extended to deal with a horizontal wire antenna located over a layered half-space. As before, the exact solution so obtained is reduced to known special cases for the T.M.(transverse magnetic) and T.E. (transverse electric) radiated fields. These expressions are valid for zero or small heights above the air/ground interface. The application to a flat lying butterfly antenna, as a source, is also outlined.

ISSN:0920-5071    

DOI:10.1163/156939396X00379

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The finite difference time domain (FDTD) formulation for nonuniformly meshed computational space with inhomogeneous lossy dielectrics is presented and discussed. The use of the nonuniform mesh allows for the analysis of practical geometries with modest computer resources. The selection of FDTD parameters in both time and spatial domains, and its influence on the numerical results is also addressed. Comparisons of numerical results with available measured data show good agreement. This FDTD formulation is applied to study the minimization of crosstalk between coupled microstrip lines. Different techniques are investigated to reduce the coupling, such as an air notch, a PEC doping, a PEC cover, and some related combinations. The numerical analysis of this study shows that the best techniques for crosstalk reduction with only one specific cover height and a limited range for the other microstrip line parameters, is obtained by applying the combination of a PEC doping and a PEC cover.

ISSN:0920-5071    

DOI:10.1163/156939396X00388

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

In this paper we study the incorporation of wavelet-transforms into the source-model technique (SMT) for efficient analysis of electromagnetic scattering problems. The idea is to divide the discrete sources into groups of arrays with wavelet amplitude distributions. We refer to these array sources as fictitious wavelet array sources. They can be readily formed by applying appropriate wavelet transformations to the original matrix equation obtained based on a conventional SMT solution. The transformed impedance-matrix obtained in this manner is then compressed and thus a substantially smaller matrix equation has to be solved. The conventional as well as the windowed Fourier transform variant of the wavelet transform are considered. The ease with which one can adjust the expansion for resolution of small features and for handling small perturbations in the scatterer geometry is demonstrated. A comparison with a conventional method of moments solution is presented to show the advantages and disadvantages of the new approach.

ISSN:0920-5071    

DOI:10.1163/156939396X00397

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor