摘要:

A previous analysis for two thin wires is extended to the case of N thin wires. An exact expression for the scattered field in the interface is obtained. The radiation field in the upper half-space is also considered employing a simple asymptotic argument.

ISSN:0920-5071    

DOI:10.1163/156939392X00102

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The class of problems to which the Finite-Difference Time-Domain (FDTD) method can be applied is extended through the use of near and far-field projection techniques. These methods are developed by applying the equivalence principle to a surface within the FDTD problem space. Algorithms are found to project the equivalent electric and magnetic currents on this surface to any point in space either in the time or the frequency domains. A summary of extensive validation and error checking results is presented which shows the routines to be robust and accurate to within a few percent. As a result, the FDTD approach can be applied to a number of previously impractical problems.

ISSN:0920-5071    

DOI:10.1163/156939392X00995

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Complete polarimetric signatures of a canopy of dielectric cylinders overlying a homogeneous half space are studied with the first and second order solutions of the vector radiative transfer theory. The vector radiative transfer equations contain a general nondiagonal extinction matrix and a phase matrix. The energy conservation issue is addressed by calculating the elements of the extinction matrix and the elements of the phase matrix in a manner that is consistent with energy conservation. Two methods are used. In the first method, the surface fields and the internal fields of the dielectric cylinder are calculated by using the fields of an infinite cylinder. The phase matrix is calculated and the extinction matrix is calculated by summing the absorption and scattering to ensure energy conservation. In the second method, the method of moments is used to calculate the elements of the extinction and phase matrices. The Mueller matrix based on the first order and second order multiple scattering solutions of the vector radiative transfer equation are calculated. Results from the two methods are compared. The vector radiative transfer equations, combined with the solution based on method of moments, obey both energy conservation and reciprocity. The polarimetric signatures, copolarized and depolarized return, degree of polarization, and phase differences are studied as a function of the orientation, sizes, and dielectric properties of the cylinders. It is shown that second order scattering is generally important for vegetation canopy at C band and can be important at L band for some cases.

ISSN:0920-5071    

DOI:10.1163/156939392X00120

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

DyadicGreen's function (DGF) technique is a very efficient means of dealing with the electromagnetic boundary-value problems. In this paper, the dyadic Green's function of ionospheric waveguide was constructed on the basis of quasi-parabolic electronic concentration distribution of the inhomogeneous ionosphere. As a practical application, two physical models with sources in ionosphere and at the earth's surface were discussed. The coefficients of dyadic Green's functions corresponding to the two models were derived by using the boundary conditions of DGF at the interfaces. The forms of dyadic Green's functions possesses a pretty good symmetry with regard to the source and observed points. Although the consideration was based on two special physical models, the final results can be generally used to the practical problems with slow variation relative permittivity with regard to the radial coordinate.

ISSN:0920-5071    

DOI:10.1163/156939392X00139

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The WKB method is applied to wave propagation in stratified bi-isotropic media, or nonreciprocal chiral media, for waves with normal incidence. The method is based on the expansion of self-dual fields, which are certain combinations of the electric and magnetic fields. The propagating fields are derived with the WKB method. For sufficiently slowly varying media, the reflected fields are obtained as a first-order correction to the WKB solution. For normal incidence, the reflection effect is independent of the chirality parameter κ but depends on the nonreciprocity parameter Χ.

ISSN:0920-5071    

DOI:10.1163/156939392X00148

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We describe a novel optoelectronic technique to generate and detect THz electromagnetic waves by using large-aperture planar photoconductive antennas and antenna arrays. This approach is an effective method of producing directional and steerable sub-millimeter wave pulses in free space.

ISSN:0920-5071    

DOI:10.1163/156939392X00157

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The problem of scattering of electromagnetic waves from anisotropic irregularities, generated by turbulence in the atmosphere, was considered in Born approximation. A valid solution is found not only for the Fraunhofer zone but also for the Fresnel zone of the antenna. In this case no limiting conditions on correlation length of refractive index irregularities appear and there are only limitations on radar range. It is shown that the scattered power, measured at the output of the receiving antenna, mainly depends on the degree of anisotropy and angular width of the antenna pattern. Received power increases with the increasing of anisotropy, but then saturates at a level which depends on the antenna parameters.

ISSN:0920-5071    

DOI:10.1163/156939392X00166

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The electro-motive force V induced across an electrical conductor carried by the Earth through the galactic magnetic field is calculated in detail from first principles. It is shown that the induction is large enough for the effect to be measurable.

ISSN:0920-5071    

DOI:10.1163/156939392X00175

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939392X01066

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939392X00184

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor