Study of in-situ measurement of underwater complex dielectric constant in frequency of under 10 MHz

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K14517
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Naval and maritime engineering
• Research Institution: Japan Agency for Marine-Earth Science and Technology
• Principal Investigator: YOSHIDA Hiroshi 国立研究開発法人海洋研究開発機構, 海洋工学センター, 部長 (00359134)
• Research Collaborator: MACHIDA Shigenori
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 海水 / 複素誘電率 / 導電率 / 深海 / 容量法

Outline of Final Research Achievements

To realize complex dielectric constant of seawater in frequency of under 10 MHz, I have tried to develop an in-situ dielectric meter．The research work consists of two major parts: development of an in-situ measurement unit and of an underwater sensor unit. A commercial LCR-meter and its remotely control system are installed in a pressure hull for the mesurement unit. A capacitive sensor is adapted as the sensor unit but it is difficult to remove errors caused by sensor configuration and extract capacitive term which becomes very small in seawater. I had tried making prototypes three times during this research period. In the end of the research, unfortunately, I could not reach the goal. In future I will conduct this research and then reach the goal.

Free Research Field

海中電磁気学

Academic Significance and Societal Importance of the Research Achievements

海中での交番電流や磁界の海底下探査利用は古くからなされており，数十kHzの周波数は潜水艦に向けた低速通信に利用されているが，これら以外の応用はなかった．しかし，海中での音波利用は限界があり他の媒体をもちいた通信や測位の手法が求められている．こうした要求にこたえるためには，海中の低周波電磁波伝播と海中送受信アンテナの研究が必須であるが，これらのバックグランドパラメータである複素誘電率が重要となる．しかし，in-situの海中の複素誘電率計測例はなく，また導電性が支配的である海水の誘電率を計測する手法が確立されていない．このような背景から本研究の目的が達せられることには非常に大きな意義がある．