Field Experiment of a Circularly Polarized Underwater Antenna

A half sheath dipole antenna (HSDA) has been investigated as one of practical antennas for various underwater applications such as wireless communication systems. However, a wireless communication system using HSDAs may suffer from poor connectivity when antennas are perpendicularly arranged because HSDAs are linearly polarized antennas with high cross polar discrimination (XPD). To overcome this problem, we propose a quadrature feed circularly polarized half sheath antenna (Q-HSA) consisting of two vertically crossing HSDAs, which ideally shows 0-dB XPD. A Q-HSA and a HSDA are designed at the frequency of 100 kHz and are prototyped to measure their characteristics at real sea. Measured results show that the Q-HSA outperforms the HSDA because the variation of the received power by the Q-HSA while rotating, up to 4 dB, is extremely lower than that of the HSDA. We believe the proposed Q-HSAs expand the communicable area of underwater wireless communication systems.