UCRL-52228-Analysis of Wire Antennas in the Presence of a Conducting Half Space, Part III-The Buried Antenna.pdf (original) (raw)
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AN APPROXIMATIVE MODEL FOR ANALYZING VERTICAL ANTENNAS ABOVE A GROUND PLANE
2004
One of the research results considering the influence of the ground conductivity on the characteristics of wire structures placed above ground, which is expressed by the Sommerfeld's Integral Kernel–SIK (1909.,[1]), is presented in this paper. A new simple model for the SIK is proposed. Besides simplicity, the model should be general and should give output numerical results (for the unknown current distribution-UCD, for the input impedance/admittance, near and far EM field) of satisfying accuracy.
Radio Science, 2009
1] This paper presents a procedure to extend the methods of moments in time domain for the transient analysis of thin-wire antennas to include those cases where the antennas are located over a lossy half-space. This extended technique is based on the reflection coefficient (RC) approach, which approximates the fields incident on the ground interface as plane waves and calculates the time domain RC using the inverse Fourier transform of Fresnel equations. The implementation presented in this paper uses general expressions for the RC which extend its range of applicability to lossy grounds, and is proven to be accurate and fast for antennas located not too near to the ground. The resulting general purpose procedure, able to treat arbitrarily oriented thin-wire antennas, is appropriate for all kind of half-spaces, including lossy cases, and it has turned out to be as computationally fast solving the problem of an arbitrary ground as dealing with a perfect electric conductor ground plane. Results show a numerical validation of the method for different half-spaces, paying special attention to the influence of the antenna to ground distance in the accuracy of the results. Citation: Fernández Pantoja, M., A. G. Yarovoy, A. Rubio Bretones, and S. González García (2009), Time domain analysis of thin-wire antennas over lossy ground using the reflection-coefficient approximation, Radio Sci., 44, RS6009,
Radio Science, 1987
TlJe electric-field integral equati{q• fi,r the current on a thin. horiz{mlal wire alitenna r•tdiat. i•g above a lossy half-space is solved by the method {•f moments. with the effect of interface i•cluded via the Sommerfeld integra. Is, the well-known reflection-coe•cient approximation and the high-contrast approxiination. A modified implementation of the reflection-coefficient approximalion is suggested, which makes this technique reasonably accurate for aniennas near the interface. A comparison is made between the methods for several cases of practical interest. The high-contrast approximation is shown to be superior to the reflection-coetSficient approximation. 1. INTRODUCTION The key to a successful application of the •nt. egral equation technique for solving wire antenna pr(•blems involving the lossy halLspace is the e•c•ent, accurate computation of the Som-•erfeld i•tegrals. The evaluation of these inl egrals by rigorous approach is computationally expensive in most practical problems where the integrals must be computed many times. The solution time can be substantially reduced by employing the interpolation technique within the
Antenna Ground-Modeling Antennas Near to and Penetrating a Lossy Interface
Abstruct-A technique for modeling wire objects interacting across or penetrating the planar interface which separates two half-spaces is described. The moment-method treatment is employed, based on the thin wire approximation to the electric-field integral equation, with the effect of the interface included via the Sommerfeld integrals. The compotation time associated with evaloating the latter is substantially shortened by using au interpolation-based technique plus asymptotic field expressions. Although developed specifically for the wire problem, the procedure is also applicable, with slight modification, to modeling d a c e objects as well. Special care is taken to account for the charge discontinuity that OCCIUS at the point a wire penetrates the interface. Example calculations are shown for a monopole antenna driven against ground stakes and simple ground screens, the fields of buried objects, and a simple electromagnetic pulse (EMP) simolator. T
An integral equation method (based upon the electric field) for the analysis of a vertical antenna located in free space near the interface with a lossy half-space is presented. Two methods are considered to account for the influence of the interface-reflected fields upon the antenna current distribution: (1) the rigorous Sommerfeld integral approach and (2) a plane-wave reflection coefficient approximation. Numerical results for antenna impedance from the two methods are compared. It is found that for the parameter variations studied, the reflection coefficient approximation provides results within 10% of those obtained from the rigorous approach at approximately 1% of the computer time The reflection coefficient technique has the further advantage of being readily extended to arbitrary antenna geometries and orientations. On presente une mothode &equation integrale pour !'analyse du champ electrique d'une antenne verticale placee dans le vide pres de la surface d'un demi-espace dissipatif. Deux methodes sont considerees pour tenir compte de l'influence des champs reflechis a la surface de separation sur la distribution de courant dans l'antenne : (1) le traitement rigoureux par l'integrale de Sommerfeld et (2) une approximation utilisant le coefficient de reflexion d'une onde plane. Les resultats numeriques pour !Impedance d'antenne calcules par ces deux methodes sont compares. On trouve que pour les valeurs des parametres considerees, l'approximation du coefficient de reflexion donne des resultats compatibles a 10% pres avec ceux qu'on obtient par le traitement rigoureux, avec seulement environ 1% du temps d'ordinateur. La technique du coefficient de reflexion a l'avan-tage d'être facilement generalisable a des geometries et des orientations d'antenne arbitraires.
An integral equation approach for the analysis of a horizontal wire antenna(s) Ilicated in free space near a lossy half-space is described. Two methods, a rigorous one based upon the Sommerfeld formulation and an approximation technique involving the Fresnel plane-wave reflection coefficients, are used to account for the influence of the interface-reflected field upon the antenna current distribution. A moment method (subsectional collocation) solution procedure is used to obtain numerical results for antenna impedance and radiation patterns. The reflection coefficient approach is found to agree well (generally within in) with those due to the rigorous method at a fraction (approximately 1",;,) of the computer cost.
Simple Numerical Approach in Analysis of Horizontal Dipole Antennas Above Lossy Half-Space
Many antennas and antenna systems, depending on their purpose, are installed in close proximity to the ground or even directly on it. Because of its great practical importance, radiation from a horizontal dipole antenna above a conducting half-space has been a subject of research of many scientists during the last century. Influence of the lossy ground on antenna characteristics is expressed by two types of Sommerfeld`s integrals that do not have a closed-form solution. The goal of this paper is to present a simple, generally applicable procedure for their satisfyingly accurate approximation. Proposed methodology will be applied to calculation of the current distribution along the conductors of the horizontal dipole antenna. Obtained results will be compared to corresponding ones available in the literature. Figure. 6. Amplitude of normalized current distribution on a double-wave HDA above LHS.