Electrical and Computer Engineering ETDs

Publication Date

10-6-1966

Abstract

The problem of radio wave propagation using antennas submerged in sea water has received much attention in recent years. As early as 1940 Norgorden [1] prepared a paper on the problem of propagation of radio waves from a transmitting antenna in air to a receiving loop antenna in sea water. Further work on the loop antenna was performed in 1946 by Quinn and Norgorden [2]. An analysis of a Hertzian dipole in an infinite, conducting medium was done by Tai [3] in 1947. He showed that a meaningful expression for the radiation resistance of the Hertzian dipole in a conducting medium can be obtained only if the dipole is insulated. Electric and magnetic dipoles in infinite and semi-infinite media have been analyzed by several investigators since 1947; e.g., Moore [4] , Lien [5] , Banos and Wesley [6] , Wait [7],[8], and King [9]. Experimental work was done in 1960 by Kraichman [10] to verify the results of Wait and Banos, and by Held [11] to verify the exponential increase of attenuation with depth.

An extensive analysis of the submerged antenna problem was presented by Moore [4] in 1951. Moore analyzed the problem of the propagation of an electromagnetic wave through sea water (a conducting medium), through the boundary between the sea water and the air (a dielectric), and over the surface of the sea water. He treated the electric and magnetic dipoles in a conducting medium and analyzed three antenna configurations in this medium: the biconical antenna, the “coaxial antenna", and the small magnetic loop. In addition, Moore analyzed the power requirements for a system consisting of submerged sending and receiving antennas. The coaxial antenna had been analyzed theoretically and experimentally by Flath and Norgorden, [12] in 1949 as a "lossy concentric line''. However, this work was not available to Moore when he did his work. The results of these two independent investigations agreed closely.

This paper analyzed two specific types of submerged antennas. The first of these is the coaxial antenna introduced by Fl.th and Norgorden and later independently by Moore; the second is the toroidal antenna suggested by Anderson [13]. A theoretical analysis, followed by experimental verification, is presented for each type of antenna.

The theoretical analysis of the coaxial antenna in this paper is based on Moore's work. The purpose of the experiment which followed was to model the coaxial antenna immersed in the sea. In order to represent the size of the sea adequately by a large tank which could be kept indoors, the antenna was scaled to operate in a frequency range from 50 to 120 mc. All assumptions made in the theoretical analysis were investigated to insure that they applied to the scaled model.

Anderson derived an expression for the dipole moment of the toroidal antenna girding a conducting prolate spheroid. This paper extends Anderson's work to include a discussion of the input impedance for the same case. The antenna is treated theoretically as a transformer with the sea water as the secondary winding. The experimental results are interpreted in terms of the transformer equivalent circuit. A scaling frequency of one mc was selected because of the properties of the ferrite magnetic core used and the size of the saltwater tank available.

Document Type

Thesis

Language

English

Degree Name

Electrical Engineering

Level of Degree

Masters

Department Name

Electrical and Computer Engineering

First Committee Member (Chair)

Ruben David Kelly

Second Committee Member

Donald Childress Thorn

Third Committee Member

Richard H. Williams

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