摘要:

The ability to focus electromagnetic fields into a lossy dielectric region is considered for the case where a thin highly conducting sheet is located between the source aperture and the observer. An exact formulation is presented for the aperture illumination which may be any function of the horizontal (x, y) coordinates. The resulting expressions for the fields in the homogeneous dielectric region, above or below the thin conductive sheet, are evaluated numerically for selected cases. In particular, it is shown that the presence of the sheet does not impair the quality of the focus to any major extent, but the amplitude of the field is diminished significantly. The double numerical integration routines are validated by developing relatively simple asymptotic expressions for the fields which also can be employed as dependable field predictors for regions not near the array.

ISSN:0920-5071    

DOI:10.1163/156939393X00192

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A banded matrix iterative approach is applied to study scattering of a TE incident wave from a perfectly conducting one-dimensional random rough surface. It is much faster than the full matrix inversion approach or the conjugate gradient method. When compared to the Kirchhoff iterative approach, it is of comparable CPU time, and works for cases when the Kirchhoff iteration is erroneous. The method is illustrated for a variety of parameters with particular application to large scale rough surface problems. The largest surface length used is 400 wavelengths with 3200 unknowns, and all the coherent wave interactions are included within the entire surface length. The accuracy of the banded iterative approach is demonstrated by showing that the results overlie those of the exact matrix inversion and the conjugate gradient method. The numerical method is also easy to implement. With this approach, we are able to compute the new response characteristics of composite rough surfaces with much larger scales. The case of large incidence angle is also studied. Comparison is also made with the analytic second-order Kirchhoff theory.

ISSN:0920-5071    

DOI:10.1163/156939393X00200

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A numerical algorithm to analyze the plane-wave three-dimensional oblique incidence on a strip grating is presented. Electromagnetic field is decomposed into vector Floquet harmonics of the E-type and H-type modes. To impose boundary conditions on the incident, reflected and transmitted waves, two integral equations of Fredholm of first kind are obtained. These equations are solved numerically with the standard Galerkin procedure, and the convergence of the algorithm is examined numerically. Since the superficial current near the edges of a conducting strip have been taken into account, the computational algorithm shows a fast convergence. Results are compared with other numerical results available in the literature to demonstrate the accuracy of the proposed method. Some numerical results are shown at normal and oblique incidence, to make clear the behaviour of the grids at different azimuth incidence angles.

ISSN:0920-5071    

DOI:10.1163/156939393X00219

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A method for numerically extracting the diffraction and surface wave scattering mechanisms present in the coated edge is described. An exact boundary integral formulation is used without resorting to the impedance boundary condition approximation. To handle the semi-infinite problem numerically, the non-decaying physical optics (PO) and surface wave fields are removed from the boundary integral equation such that the final discretization domain involves only a finite region near the edge. Numerical diffraction coefficients and surface wave launch coefficients are extracted from the scattered field. Solutions to several finite sized coated strips are constructed using the numerical diffraction coefficients and are shown to be valid for a variety of strip configurations.

ISSN:0920-5071    

DOI:10.1163/156939393X00228

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The corner constant, which serves to correct the internal impedance per unit length of a conductor, is calculated in closed form for the limit of small ratios of internal to external magnetic permeabilities for a right angle corner. The perfectly conducting external tangential magnetic field distribution is used in an internal Green's theorem representation to determine the axial electric field. The corner constant is then determined by an integration of the surface axial electric field and the perfectly conducting magnetic field. Expansions of the axial electric field are also given because of its utility in future papers. A rotation of the radial coordinate into complex values is used to reduce the corner constant to a known complex phase times a real constant. This rotation is valid for general real ratios of internal to external magnetic permeabilities as a result of the analyticity of the fields in a sector above the positive real axis of the radial coordinate.

ISSN:0920-5071    

DOI:10.1163/156939393X00237

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In this paper, the orbital diversity configuration which is one of the suggested protection schemes foreseen for satellite paths operating at frequencies above 10 GHz, to overcome the high rain-induced attenuation, is discussed. More particularly, a recently proposed methodology for the prediction of the outage performance of an orbital diversity system based on the lognormal assumption is modified to include the gamma form for the rainfall and attenuation distributions. This is probably the case for Japan and other locations with similar climatic conditions. Numerical results are compared with the only available set of experimental data taken from an operated system located at Fucino, Italy, where the existing single attenuation distribution best fits the gamma form. The agreement was found to be quite good.

ISSN:0920-5071    

DOI:10.1163/156939393X00246

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The feasibility of utilizing bistatic scattered field data to obtain the microwave ISAR image of a target is investigated. The principle and results of the bistatic imaging algorithm are presented. It is shown that the ISAR image can be reconstructed by Fourier inversion of the bistatic scattered field data under the physical optics approximation. Bistatic scattered field data is faster to simulate using the shooting and bouncing ray technique than monostatic scattered field data hence the bistatic scheme results in time savings. Monostatic and bistatic ISAR images are presented for different targets. The tradeoff between time savings and image fidelity for the two schemes is discussed.

ISSN:0920-5071    

DOI:10.1163/156939393X00255

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939393X00264

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939393X00273

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor