Analysis of Degradation of Transmission Characteristics of Underwater Antenna due to Metal Enclosure of Autonomous Underwater Vehicle

The Autonomous Underwater Vehicle (AUV) is anticipated as a means of collecting underwater visual information using its built-in camera. While underwater radio wave communication via underwater antennas has been developed as a means of information collection, it is expected that the metal casing of AUV may adversely affect the transmission characteristics of antennas in underwater radio wave communication. Therefore, this report evaluates the impact of AUV’s metal casing on antenna-to-antenna communication using an electromagnetic field simulator. The evaluation indicates that when the size of the antennas is larger than the AUV’s metal casing, the impact on transmission characteristics is minimal even when the AUV is positioned between the antennas. On the other hand, when the metal casing is larger than the antenna size, the transmission characteristics between antennas degrade due to eddy currents flowing in the metal casing induced by antenna currents. Consequently, it is suggested that when attaching underwater antennas to AUVs, maintaining relatively good transmission characteristics, even with smaller antennas, is possible by appropriately configuring the size relationship and placement of the metal casing relative to the antennas.