摘要:

A new ansatz is formulated, whereby a large class of focus wave mode (FWM)-type finite energy localized wave (LW) solutions to the axisymmetric 3-D Klein-Gordon equation is obtained by means of a dimension (or coordinate)-reduction technique. Each of these solutions consists of a product of a specific solution to the 1-D scalar wave equation, with coordinates z and t, and, essentially, an arbitrary analytic solution to the 1-D Klein-Gordon equation, with coordinates Z and T appropriately defined in terms of z, t and the polar radial coordinate p. In the absence of dispersion, the same formalism, but with a different definition of the coordinates Z and T, can be used to obtain FWM-type finite energy localized wave solutions to the 3-D scalar wave equation. In this case, the aforementioned ansatz is intimately related to a technique due to Bateman [1, 2].

ISSN:0920-5071    

DOI:10.1163/156939300X01283

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The scattering from multiple multilayered eccentric bianisotropic cylinders is studied at first in the most general case based on the boundary-value approach combined with the generalized separation variables method and the indirect modeling technique according to the equal volume principle. The solution is developed and expressed in terms of a system of simultaneous linear equations of infinite order which is then truncated for numerical computations, and the normally incident wave can be either TEz- or TMz-polarization. Numerical investigation is performed for the co- and cross-polarized echo widths in the far field zone, and the multiple scattering features are demonstrated for various two-dimensional bianisotropic cylindrical composites corresponding to different constitutive models, such as uniaxial and gyrotropic forms, as well as the combination of ordinary ferrite with bianisotropic media.

ISSN:0920-5071    

DOI:10.1163/156939300X01292

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The electromagnetic properties of cavity-backed apertures loaded with nonlinearly-loaded, electrically small dipole antennas are studied with an extended FDTD simulator. A nonlinearity in the antenna load is introduced by connecting a nonlinear circuit to the dipole antenna. The simplest nonlinear circuit, a nonlinear diode in series with a resistor, is treated in detail to illustrate the effects of a device that will generate well-defined harmonics to any driving frequency. Computational results are generated for both TM and TE cases and for broadband and narrowband excitations. The extended FDTD simulations show that various EMC and RCS effects associated with the presence of a nonlinearly-loaded electrically small dipole antenna are closely connected to the resonant features associated with the cavity-backed aperture. It is illustrated that if the antenna position is properly correlated to peaks of the modal distribution supported by the open cavity, then the fields associated with frequencies generated by the nonlinear load can be coupled significantly to other elements or structures within its interior. It is further demonstrated that the fields generated within the interior of the cavity can be resonantly coupled to its exterior at those frequencies; hence, the scattered fields in the far field will contain information about the characteristics of the interior of the cavity and its nonlinear loading.

ISSN:0920-5071    

DOI:10.1163/156939300X01300

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Ananalytic solution of the problem of a plane electromagnetic wave scattering by a conducting spherical scatterer residing on or partially buried in an infinite perfectly conducting ground plane is formulated in conjunction with the method of images. With imaging, the geometry is replaced by two touching or overlapping spheres in the absence of the ground plane, but with the given incident plane wave and its image plane wave, in order to satisfy the boundary conditions on the ground plane in the original geometry. Numerical results for the normalized scattering cross section at an arbitrary height (or depth) from the ground plane and at any specific angle of incidence are presented graphically, and these are obtained by evaluating the scattered field coefficients by matrix inversion or an iterative scattering procedure.

ISSN:0920-5071    

DOI:10.1163/156939300X01319

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Convenient closed-form far-field expressions for thin circular loop antennas which possess a traveling-wave current distribution have been available for many years. However, a method for analytically evaluating the more complicated near-zone vector potential and corresponding electromagnetic field integrals associated with traveling-wave circular loop antennas has not been previously reported in the electromagnetics literature. The purpose of this paper is to introduce a systematic approach for finding exact series representations of these integrals which are valid not only in the far-field of the loop, but also in its near-field region. These mathematically exact solutions are general and can be shown to contain all of the well-known classical approximations as special cases.

ISSN:0920-5071    

DOI:10.1163/156939300X01328

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Thispaper introduces amplitude and phase nulling with a genetic algorithm with the intent of finding the optimum number of LSB of control needed to place multiple nulls while not significantly distorting the far field pattern. Many interference scenarios were modeled and individual runs were averaged to conclude that five LSB of amplitude and three LSB of phase control out of a total of eight bits are best for the linear array modeled. Representative samples of some of the interference scenarios modeled are shown.

ISSN:0920-5071    

DOI:10.1163/156939300X01337

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Extending previous work [1], a novel ansatz is formulated, whereby a class of X wave-type finite energy localized wave (LW) solutions ψ(p, z, t) to the axisymmetric 3-D Klein-Gordon equation is obtained by means of a dimension-reduction approach. Each of these solutions consists of a product of the zero-order X wave solution to the 3-D scalar wave equation and an analytic solution ψ1D(Z, T) to the 1-D Klein-Gordon equation, with variables Z and T appropriately defined in terms of z, t and the polar radial coordinate p. In the absence of dispersion, the same formalism, but with a different definition of the coordinates Z and T, can be used to obtain X wave-type finite energy LW solutions to the 3-D scalar wave equation.

ISSN:0920-5071    

DOI:10.1163/156939300X01346

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The integral equations governing the electromagnetic scattering by bodies of revolution involve the computation of what are called the modal Green's functions. These functions are evaluated repeatedly. Hence, any saving in time while computing these functions will be reflected on the overall time of computation. These functions are usually evaluated using an adaptive numerical integration technique. In this work, an exact series form is obtained to efficiently evaluate these functions. An acceleration technique is used to speed up the series convergence. The method can be implemented in existing codes. It is shown that a significant saving in the time of computation is achieved using the series form.

ISSN:0920-5071    

DOI:10.1163/156939300X01355

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

We show how integral equations can be used to solve boundary value problems of the scalar Helmholtz equation with Dirichlet and Neumann boundary data supplied on a circular cylinder. An application is given to the scattering of a TM electromagnetic wave on a corrugated perfectly conducting cylinder. We discuss when these integral equations can be used.

ISSN:0920-5071    

DOI:10.1163/156939300X01364

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The differential rain attenuation is considered to be one of the main propagation factors causing interference between adjacent Earth-Space paths. In the present paper, an existing method to predict the differential rain attenuation statistics is properly modified to include a more complicated but accurate estimation of the slant path lengths affected by the rain medium. The modified method is oriented to be generally applicable, particularly in the case of satellite paths operating under low elevation angles in the Ku-band, where the accurate estimation of the effective slant path lengths is very critical. The present results are compared with a set of available simulated data for the differential attenuation over pairs of paths located in Montreal. The influence of various other parameters such as the geographic latitude and climatic zone is also examined.

ISSN:0920-5071    

DOI:10.1163/156939300X01373

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor