摘要:

This paper is a contribution to the study of the diffraction of an electromagnetic plane wave by a cylindrical rod of arbitrary cross-section and optical index. The incident wave vector is not necessarily perpendicular to the rod. This vectorial diffraction problem is solved using the method of fictitious sources which has proven to be effective for scalar problems. Theoretical and numerical aspects are both studied.

ISSN:0920-5071    

DOI:10.1163/156939394X00786

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In this paper, the radiation properties of an annular slot antenna of infinitesimal aperture and radius a, cut in an infinite ground plane and covered by a dielectric cylinder of finite height, are investigated analytically. The excitation is assumed to be a circumferentially constant voltage at the slot opposite edges. The unknown electromagnetic field is expressed using the mixed mode spectrum of a radial dielectric waveguide. Then, by enforcing the satisfaction of the appropriate boundary conditions, an integral equation is derived in terms of the unknown electric field distribution Ez. This equation is solved by employing Galerkin's technique and the electromagnetic field distributions are computed in all the regions of the 3-D space. Finally, based on these results, the input impedance and the far field pattern of the antenna are obtained. Numerical results are presented for several cases.

ISSN:0920-5071    

DOI:10.1163/156939394X00795

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A numerical study of the polarimetric thermal emission from ocean surfaces randomly rough in one dimension using a Monte Carlo technique is presented. In this study, a set of finite length surface profiles with desired statistics was generated using a spectral method. Each surface was extended periodically to create an infinite rough surface, and the thermal emission was computed using the extended boundary condition method (EBC) and the method of moments (MOM). The results from the set of surfaces were then averaged to obtain the Monte Carlo estimate of polarimetric thermal emission. The surface statistics chosen were intended to model a wind perturbed ocean surface in the X to Kuband microwave region. The results of the study show that the third Stokes parameter, UB ,is sensitive to the azimuthal angle between the surface periodicity and the looking angle, the rms height of the surface, and the surface power law spectrum slope, and that this parameter is insensitive to variations in polar angle, permittivity, and surface spectrum high frequency content.

ISSN:0920-5071    

DOI:10.1163/156939394X00803

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The T-matrix approach is applied to formulate electromagnetic scattering from an arbitrary number of spheres due to an incident plane wave. The representation of an incident plane wave in spherical vector wave functions from an arbitrary incident direction is given to facilitate subsequent derivation. The T-matrix formulation for an arbitrary number of spheres is obtained in two forms: an iterative form and a recursive form. It is shown that the recursive form is much more efficient than the iterative form when the number of spheres is greater than 2. The representations of the radar cross section, extinction and scattering cross sections in T-matrix form are provided. Numerical illustrations are given showing comparisons with calculations made by other investigators.

ISSN:0920-5071    

DOI:10.1163/156939394X00812

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Time marching algorithms are often used to compute the current induced on a conductor by an incident pulsed electric field. They are obtained by discretizing the relevant equations on a uniform mesh whose spacing is determined by the frequency of the incident field; higher frequencies requiring a finer mesh. Unfortunately it is often observed that the error in the numerical solutions of time domain field integral equations grows exponentially when the incident field has high frequency. We show here that this happens when the numerical approximation used to solve the integral equation part of the field equations is unstable, and that it is just as important for this part of the scheme to be stable as it is to ensure that the PDE approximation satisfies a CFL type condition. We present a rigorous numerical stability analysis of time marching schemes for the electric field integral equation on a flat plate. This yields a stability test for such schemes which is relatively quick and simple to implement. We use numerical test results obtained for schemes derived by Rynne & Smith to illustrate the value of our theoretical predictions.

ISSN:0920-5071    

DOI:10.1163/156939394X00821

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A family of mixing formulas is generalized in this paper to cover mixtures where dielectrically anisotropic spherical inclusions are embedded in isotropic host material. The usual limitations of quasistatic mixing rules apply also here that the inclusions should be small compared with wavelength. Special emphasis with numerical examples and illustrations is focused on the case where the inclusions are randomly oriented in the mixture, making the mixture isotropic. The result is a general mixing formula from which special cases can be extracted, among others the generalizations of Maxwell-Garnett, Effective Medium, and Coherent Potential formulas.

ISSN:0920-5071    

DOI:10.1163/156939394X00830

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

An electron rotating under the influence of a magnetic field can be accelerated by a resonant rotating RF electric field. To prolong this interaction the magnetic field is inhomogeneous in space (magnetic mirror), and time varying for the dynamic adjustment of the synchronism. The acceleration process is described by the relativistic and nonlinear equations for the motion and the fields. The process can be better understood through simulations which predict the electron trajectory and the gain in kinetic energy under various field configurations. The simulation program was tested for cases with known results with good agreement. Subsequently, many simulations were done for the general case to investigate the influence of the injection position and velocity of the electron, and the configuration and strength of the fields. Critical comparison of these results allowed optimization for maximum energy gain.

ISSN:0920-5071    

DOI:10.1163/156939394X00849

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939394X00858

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939394X00867

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor