摘要:

An analysis is given for determining the aperture illumination on the surface of a conducting half-space when a component of the sub-surface electric field is prescribed. No far field or quasi-near field approximations are made. For the examples considered the conduction currents are comparable with the displacement currents. Physical limitations of the procedure are identified. A forward confirming calculation is performed by discretizing the aperture distribution by an array of 64 magnetic dipoles.

ISSN:0920-5071    

DOI:10.1163/156939393X00381

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The scalar wave equation in a curvilinear coordinate system is considered first as a model for wave propagation in nonplanar stratified media. The phase velocity is assumed to vary in a direction normal to the stratification of the scattering object. A spatial integral transform is used to reduce the problem to a problem with one spatial dimension. A nonphysical wave splitting is introduced which leads to simplifications for the inverse scattering problem. The imbedding equation for the associated reflection kernel is obtained. Numerical results for the reconstruction of the phase velocity for a stratified circular cylinder and a stratified sphere are presented. Electromagnetic scattering from a stratified circular cylinder or sphere is then treated in vector form by an analogous approach. In an inverse problem the permittivity is reconstructed.

ISSN:0920-5071    

DOI:10.1163/156939393X00390

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The semi re-entrant microstrip section is a useful structure for the realization of high levels of coupling between two microstrip lines. In this paper, the semi re-entrant structure is comprehensively analyzed by employing a spectral domain formulation. Using the results obtained from the analysis procedure, the parameters of an equivalent TEM transmission line coupler are calculated. This enables one to design a semi re-entrant coupler through the utilization of conventional design methods. Numerical analysis results as well as some design data are also included.

ISSN:0920-5071    

DOI:10.1163/156939393X00408

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

An asymptotic theory is developed for the electromagnetic field near a smooth convex, impedance or perfectly-conducting, surface in the shadow region of an incident ray-optical wave. The theory is based on Fock's postulates and represents an extension of his method of parabolic equations from penumbra to shadow. The new results include the cross-polarization effect for a torsional surface ray on an impedance surface and an adiabatic creeping mode solution for a ray with varying curvature on such a surface.

ISSN:0920-5071    

DOI:10.1163/156939393X00417

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A moment method formulation of the determination of the equivalent network parameters of an inclined strip extending between the opposite broad walls of a rectangular waveguide is given in this paper. The integral equation representing the boundary condition of the tangential component of electric field along the length of the strip is converted into a matrix equation using a pulse function and point matching technique. From a knowledge of the coefficients of the basis function, the complex reflection coefficient and hence the equivalent network parameter is determined. Comparison between the theoretical and the experimental results is also presented. The perturbation of the wall current in the vicinity of the obstacle is also studied.

ISSN:0920-5071    

DOI:10.1163/156939393X00426

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In this second part in a three part sequence, the hybrid wavefront-resonance scheme developed in Part I is applied and explored numerically for the transient field scattered by a plane parallel waveguide cavity configuration. Emphasis is on validating the effectiveness of this representation and on explaining the observed features in the scattered signal at early, intermediate, and at late observation times. Utilizing results reported earlier for the complex resonances [3], it is shown that the late-time observables carry the signature of a cluster of high-Q internal resonances that occurs near modal cutoff frequency, in the form of a slowly decaying typical waveform which is independent of the incident angle or the excitation pulse but is related to the cavity dimensions. The early-time field is expressed as a rapidly decaying series of external wavefront interactions, while at intermediate times the internal resonances synthesize the dispersive guided mode return. The convergence of the resonance series, and its role in establishing the early-time causal wavefront are explored. By properly selecting the incident angle and pulse-shape, one may de-emphasize the early-time contributions and enhance the magnitude of the late time typical waveform.

ISSN:0920-5071    

DOI:10.1163/156939393X00435

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Conditions for replacing a bi-isotropic half-space by an impedance surface are formulated. The most general bi-isotropic surface impedance is a dyadic containing an antisymmetric part, which is non-null for nonreciprocal media. To formulate the general radiation problem in front of the bi-isotropic surface, the exact image theory has been extended. The image theory is verified by known special cases and demonstrated by an example of a vertical electric dipole in front of the surface.

ISSN:0920-5071    

DOI:10.1163/156939393X00444

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In this paper we present a hybrid surface/volume integral equation method solution of scattering from inhomogeneous lossy dielectric/ferrite cylinders near the planar interface separating two semi-infinite, homogeneous half-spaces. The inhomogeneous cylinders of general cross section are of infinite extent, their axes are parallel to the interface, and the excitation is transverse magnetic to their axes. Coupled hybrid integral equations are formulated by employing both surface equivalence principle and volume equivalence theorem. In the formulation, attention is focused on minimizing the computation of Sommerfeld integrals which is often encountered in dealing with buried objects, and on reducing the number of unknowns. A moment method numerical solution technique is developed for solving the formulated hybrid integral equations. From the calculated equivalent surface current, the far-zone scattered field is determined. Data showing the equivalent current distribution and the scattered field patterns are presented and discussed for selected cylinder and two half-space parameters.

ISSN:0920-5071    

DOI:10.1163/156939393X00453

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939393X00462

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939393X00471

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor