Wideband dipole antennas with parasitic elements for underwater communications

Propagation of underwater electromagnetic signals for real-time transmission and reception of data gathered during a survey mission between an Autonomous Underwater Vehicle (AUV) and underwater sensor nodes or a docking station, continues to generate a lot of interest worldwide. To this end, underwater antennas will play a significant role in ensuring good data rates and propagation distances for various underwater applications. In this paper, the performance of two dipole antennas with different parasitic elements is assessed through simulation for usage in fresh water and 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, directivity and antenna-to-antenna distance. The results obtained show that these antennas exhibit wide bandwidth, which is important to achieve high data rates. Experimental results of the reflection coefficient of the fabricated antenna measured in fresh water are given that agree well with the simulation results.