Oluyomi Aboderin

Abstract

Abstract

Abstract
The capability of an Autonomous Underwater Vehicle (AUV) or Remote Operated Vehicles (ROVs) to communicate with underwater sensor nodes or a docking station, for the exchange or transfer of data gathered during a survey mission, requires an high-speed short-range communication link. This is important because of the global attention to the underwater communication applications. To this end, underwater antennas will play a significant role in ensuring good data rates and propagation distances for these applications. In this paper, the performance of three antennas, specifically, loop, dipole and J-pole is assessed through simulation for usage in fresh and sea water operating in the High Frequency (HF) band. The antennas were designed in FEKO, an electromagnetic simulation software and their performance is assessed in terms of bandwidth and directivity. The results obtained shows that the J-pole antenna has significant advantages in term of the measured parameters over the other antennas. Experimental results of the reflection coefficient of the J-pole antenna in fresh water are given that agree well with the simulation results. © 2017 IEEE.

Abstract
In this paper we assess the influence of the conductivity of the medium on the radiation characteristics and input impedance of a loop antenna designed for underwater communications. The initial study is based on simulation of the antenna characteristics using FEKO electromagnetic (EM) software. Additionally, an equivalent circuit model of the antenna is also obtained and simulation of the input impedance on ADS software shows good agreement with the EM simulator. It is found that the radiation pattern, of the loop antenna changes significantly with the conductivity of the medium, from freshwater to seawater. The loop antennas were built with baluns and tested in freshwater, where the insertion loss between two identical antennas and the radiation pattern of one of them were also measured. The results show good agreement with the simulations.

Abstract
The radiation characteristics of a dipole antenna when immersed in both fresh and seawater are assessed through simulation and experimental work. Simulations show that the antenna's bandwidth and radiation pattern change with the properties of the medium where it is placed, namely the conductivity of the medium. Two dipoles antennas with current baluns were built and tested experimentally in freshwater. The tests included the measurement of the insertion loss between two identical dipole antennas and their radiation pattern. The results obtained show a good agreement between the simulation and experimental results.