摘要:

Direct formulas to compute the absorption cross section of lossy dielectric discs in the Physical Optics approximation, and cylinders in the Infinite Length approximation, are derived and their validity is checked by means of the Forward Scattering Theorem. These formulas are helpful in modeling microwave emissivity from vegetation. Due to enhanced directivity of large cylinder bistatic patterns, an exact computation of emissivity of those cylinders would require a tremendous amount of computational resources. In this paper it is demonstrated that for a layer of cylinders large with respect to the wavelength, the absorption cross section direct formula allows to compute emissivity in a simple way and with acceptable accuracy.

ISSN:0920-5071    

DOI:10.1163/156939396X00559

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The idea proposed in this paper is to use a model comprising clusters of filamentary sources centered in complex-coordinate space for a more systematic analysis of two-dimensional scattering problems. In this way, each portion of the body surface is illuminated by several beams each originating from a different cluster and hence arriving at a different angle. A better approximation of a general scattering by a large body is thus furnished. In addition, due to the nature of the fields radiated by the complex filamentary sources, the impedance matrix is localized and can, with appropriate thresholding operation be made sparse with almost no degradation in the solution accuracy. Moreover, the possibility of ana priorireduction in the number of sources needed for a given excitation is facilitated. The new approach is applied to analyze electromagnetic scattering by a perfectly conducting circular cylinder excited by a beam whose axis does not intersect the cylinder axis. The new approach makes the solution more general but still very efficient. The numerical results are tested against those of the analytical solution for the problem.

ISSN:0920-5071    

DOI:10.1163/156939396X00568

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The apparent admittance of an infinite monopole antenna, driven by a coaxial line of inner radius "a" and outer radius "b" , is determined for the limit of small values of a/b , where kb « 1 Previous analytical work has determined the apparent admittance for the limit a/b → 1. These two results bracket and demonstrate the validity of earlier numerical work which determined the apparent admittance for 0 < a/b < 1 . The determination of the apparent admittance for a/b → 0 requires the asymptotic solution of an integral equation. In the derivation of the asymptotic solution to the original integral equation, a new and very curious integral equation results. This new integral equation is examined analytically and finally is solved numerically.

ISSN:0920-5071    

DOI:10.1163/156939396X00577

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939396X00586

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The scattering of electromagnetic waves by infinitely extended cylinders with non-circular cross-sections is investigated. Oblique incidence for both transverse magnetic and transverse electric cases are considered. For the analysis, the Discretized Mie-Formalism is extended to cylindrical co-ordinate systems with periodic boundary conditions. Limiting cases for circular cross-sections and perpendicular incidence are discussed. To test the present algorithm and the convergence of the computer program, the off-centered circular dielectric cylinder is an ideal example. It is shown that, this method provides a conceptual easy and general approach for a wide variety of non circular cross-sections.

ISSN:0920-5071    

DOI:10.1163/156939396X00595

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939396X00603

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The solution to the problem of electromagnetic waves scattering by an array of spheres is used to simulate the scattering by a spheroid. The scattering by an array of spheres is formulated by expressing the incident, transmitted, and scattered fields in terms of the vector spherical wave functions, and the boundary conditions are satisfied by applying the translation addition theorem for the vector spherical wave functions. The advantage of using the proposed technique is the simplicity and efficiency in computation. The modeling of a conducting or dielectric spheroid is outlined and numerical results are presented graphically and compared with those based on other available methods to show the validity of the analysis.

ISSN:0920-5071    

DOI:10.1163/156939396X00612

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The scattering of electromagnetic waves by a periodic magnetodielectric layer is solved by the new method based on the rigorous integral equations of macroscopic electrodynamics. The general moments of the solution are given. Also the computer program for the numerical solution of the proposed scattering problem is developed. Taking into account permeability along with permittivity makes it possible to investigate the scattering by magnetodielectric structures approximating the structures made of perfect metal. There is an example of such approximation in the paper. The influence of modulation of magnetodielectric layer permittivity is displayed as an example.

ISSN:0920-5071    

DOI:10.1163/156939396X00621

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939396X00630

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939396X00649

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor