摘要:

This paper reviews some of the recent techniques investigated by the authors for numerical, asymptotic and approximate evaluations of the Somraerfeld integrals. Only the summaries of the final formulations are given and their numerical characteristics are illustrated using representative numerical data. Due to space limitations, the discussion in this paper is limited to the cases where both the source and the observation points are above the lossy half-space.

ISSN:0272-6343    

DOI:10.1080/02726348108915122

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

An accurate and efficient numerical method based on the rigorous Sommer-feld theory is described for modeling antennas near an interface such as the ground. The Sommerfeld integrals are evaluated by numerical integration along contours in the complex plane and two-dimensional interpolation is used subsequently to obtain the many Sommerfeld integral values needed for the moment-method solution of an integral equation. These methods permit modeling an antenna within 10-6wavelengths of the ground for about two to four times the computation time for the same antenna in free space. Results showing currents and radiation patterns are included.

ISSN:0272-6343    

DOI:10.1080/02726348108915123

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The properties of insulated antennas that make them useful for subsurface communication or heating are discussed. Several antennas and associated feed lines suitable for use in bore holes or for insertion into tissue are analyzed and compared. The nature of lateral waves is reviewed in their relation to the source that generates them. The properties of antennas designed to excite and receive lateral electromagnetic waves are discussed and practical directional antennas and arrays for subsurface communication by means of lateral waves are reviewed.

ISSN:0272-6343    

DOI:10.1080/02726348108915124

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

A conceptually simple technique is introduced to solve the electromagnetic scattering by buried objects. The technique applies the multipole expansions in two-medium half spaces accompanied with their generalized Sommerfeld integrals to represent the scattering waves. Since the modal fields of the expansions all satisfy the boundary conditions on the planar air-earth interface, the scattering problem is reduced to solving the expansion coefficients by matching the boundary conditions on a sphere. Hence the method is very similar to that of the scattering in an infinite space using the method of separation of variables. Scattering results of buried conducting and dielectric spheres are presented. Some polarization anomalies of the scattered electric field components are observed on the earth surface. The technique can be directly applied to solve the scattering by buried non-spherical objects when the finite element method is used to treat the scatterer boundaries and inhomogenuities.

ISSN:0272-6343    

DOI:10.1080/02726348108915125

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

We analyze a two dimensional cylindrical model of the earth which Is characterized by a surface admittance with any specified azimuthal dependence. The atmospheric refractive index is assumed to be laterally uniform but It may be any continuous function of the radial coordinate. We show that the coupled mode formalism developed for this problem is consistent with previous approaches for sectionally homogeneous paths based on mode matching.

ISSN:0272-6343    

DOI:10.1080/02726348108915126

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

EM propagation over and radiation from radially varying ground systems are numerically modeled using the compensation theorem integral formulation. The source is taken to be a vertical electric dipole (VED) situated either on or above an azimuthally symmetric plane ground system having an assumed surface impedance profile which can vary arbitrarily in the radial direction.

ISSN:0272-6343    

DOI:10.1080/02726348108915127

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor