A High-Efficiency Underwater Dipole Antenna With Spherical Electrodes

Development of high-efficiency antennas and effective use of radio frequency (RF) waves propagating along the boundary of two media are crucial to utilize RF waves in seawater which has high attenuation coefficient. In this paper, we propose an antenna with spherical electrodes based on a half-sheath dipole antenna consists of two cylindrical electrodes exposed to seawater and an insulator sheath at inner half of the antenna. A theoretical study indicates that spherical electrodes minimize a loss in seawater around the electrodes and improve the transmission factor between two antennas. The effectiveness of our proposed antenna is verified by an experiment in real sea using antenna prototypes designed at 100 kHz.