VLF Mechanical Antenna Arrays for Underwater Wireless Communications.

Magnetoelectric (ME) antennas have recently been demonstrated as a promising solution for very low frequency (VLF) communications, for their 2-3 orders of smaller dimensions and better immunity to electrical interferences than conventional electric antennas. Antenna arrays are widely used as an effective approach to enhance radiation field intensity. In this work, a new type of ME antenna with high quality factor resonator is proposed to enhance the radiation field strength and efficiency for antenna arrays. By tunning all the driving signal for each antenna unit at the same frequency and in phase, the radiation field has been linearly increased with the number of antenna arrays. A total radiation field of 200 nT at 1 meter has been achieved using 12 antenna arrays, which is one order of magnitude enhancement than a single antenna unit. Furthermore, the estimation of antenna efficiency based on the theory of magnetic dipole indicates that ME antennas can potentially enhance efficiency by a square law of the number of arrays. The demonstrated results and simulation analysis provide the potential for taking advantage of a large number of ME antenna arrays for underwater wireless communications.