摘要:

This paper presents an efficient method for the near-field electromagnetic scattering by three-dimensional buried dielectric and conducting objects, in which the interaction of source antennas, the ground, and scatterers is considered. With the excitation of a linear antenna, the electric field integral equations for the antenna and buried objects, and their radiation and scattered fields are formulated, which involve two different sets of Sommerfeld integrals. Because the evaluation of such Sommerfeld integrals needs tremendous CPU time, the integration along steepesi-descent paths and leading-order approximations are introduced to accelerate the computation, in which the difference between the two sets of Sommerfeld integrals is addressed. As an example, the excitation of dipole and loop antenna is considered for the scattering by buried objects, which is important for the geophysical detection problem. Numerical results show that the efficient method can reduce tremendous CPU time compared with the numerical integration method.

ISSN:0272-6343    

DOI:10.1080/02726349808908613

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In this paper, efficient sampling representations of the electromagnetic field, radiated by a centered parabolic antenna over a plane in the near-field region and over the far-field sphere, are presented. They use a. non-redundant number of samples, which remains finite even in the case of an unbounded planar observation domain. This result relies on a proper choice of the phase factor extracted from the field expression and of the coordinates used to parameterize the domain. By making explicit reference to the minimal convex domain enclosing the antenna, the number of needed data can be significantly reduced as compared with that required by modelling the antenna as enclosed in a ball. For the considered observation geometries, precise and fast sampling algorithms of central type have been developed. The reconstruction examples assess the effectiveness of the proposed representations. At last, the stability of the algorithms, with respect to random errors affecting the data, is proved by adding uniformly distributed random errors to the exact samples.

ISSN:0272-6343    

DOI:10.1080/02726349808908614

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The evaluation of the electromagnetic field diffracted by a collection of similar metallic objects is obtained using theCharacteristic Modesfor the single scatterer as basis and weighting functions in the MoM solution of the whole scattering grid. Due to their resonant behaviour, only a few characteristic modes are required for an accurate representation of the current distribution even in presence of mutual coupling. Characteristic modes has been numerically evaluated for cylindrical scattered of different shapes and successfully applied to the computation of current density and scattered far field. Several numerical results are presented and computational advantages of. this approach over classical MoM are discussed.

ISSN:0272-6343    

DOI:10.1080/02726349808908615

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A novel and fast hybrid Finite Element Method/Method of Moments (FEM/MoM) technique in conjunction with Asymptotic Waveform Evaluation (AWE) is presented to calculate radar cross section (RCS) over a wide frequency range of a cavity-backed aperture in an infinite ground plane. The hybrid FEM/ MoM technique when applied to the cavity-backed aperture results in an integro-differential equation with electric field as the unknown variable. The electric field obtained from the solution of the integro-differential equation is expanded as a function of frequency in Taylor series. The coefficients of the Taylor series are determined using the frequency derivatives of this equation. The Taylor series is then matched via the Pad'e approximation to obtain a rational polynomial representation for the electric field, which can be used to extrapolate the electric field over a frequency range. The RCS of the cavity-backed aperture is calculated using the electric field at different frequencies. Numerical results for a square cavity, a circular cavity, and a cavity-backed microstrip patch are presented over a frequency range. Good agreement between AWE and the exact solution over the frequency range is obtained and the present method proved to be cost effective in terms of CPU time compared to calculating RCS at each frequency.

ISSN:0272-6343    

DOI:10.1080/02726349808908616

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Point matching method is adapted for calculating the scattered field from the sinusoidal periodic gratings. The results are compared with those from FD-TD and T-matrix method. Diffracting efficiency versus incident angle and energy error are examined. The beat wave for the near field is also observed. A model experiment compared with theory was made.

ISSN:0272-6343    

DOI:10.1080/02726349808908617

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor