Design of Capacitive Coupler in Underwater Wireless Power Transfer Focusing on kQ Product

Yasumasa NAKA
Kousuke MURAI

IEICE TRANSACTIONS on Electronics   Vol.E101-C    No.10    pp.759-766
Publication Date: 2018/10/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E101.C.759
Type of Manuscript: Special Section PAPER (Special Section on Microwave and Millimeter-Wave Technologies)
wireless power transmission,  underwater technology,  Q factor,  coupler,  coupling circuit,  

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This paper presents the design of a capacitive coupler for underwater wireless power transfer (U-WPT) focusing on kQ product. Power transfer efficiency hinges on the coupling coefficient k between the couplers and Q-factor of water calculated from the complex permittivity. High efficiency can be achieved by handling k and the Q-factor effectively. First, the pivotal elements on k are derived from the equivalent circuit of the coupler. Next, the frequency characteristic of the Q-factor in tap water is calculated from the measured results. Then, the design parameters in which kQ product has the maximal values are determined. Finally, it is demonstrated that the efficiency of U-WPT with the capacitive coupling designed by our method achieves approximately 80%.