2020/01/28
Keio University
National Institute of Information and Communications Technology
A group led by Senior Assistant Professor Yasuaki Monnai of the Department of Applied Physics and Physico-Informatics, Faculty of Science and Technology, Keio University, in collaboration with Senior Researcher Akifumi Kasamatsu and Principal Investigator Issei Watanabe of the National Institute of Information and Communications Technology (NICT), has developed a compact, high-resolution radar that uses terahertz waves as a probe. They have demonstrated that this radar can be used to perform non-contact measurements of heartbeat movements on the surface of a person's chest through clothing.
When terahertz waves, which have wavelengths between those of radio waves and light, are applied as radar, they enable measurements with higher resolution than radio waves and greater medium-penetration than light. However, the miniaturization of radar has been considered difficult because low-loss materials suitable for implementing phase shifters, which are necessary for beam scanning, and circulators, which are necessary for separating transmitted and received waves, in the terahertz band have not yet been found.
In this study, the research group devised a terahertz wave waveguide structure and demonstrated that by combining the symmetry of the excitation mode from a center-feed structure with the symmetry of the wave-coupling directivity inside and outside the waveguide, it is possible to achieve both beam scanning and detection simultaneously without using phase shifters or circulators. They also developed a method to calculate the direction, distance, and velocity of an object by processing data obtained from frequency sweeps, demonstrating its function as a radar. This achievement has clarified a concrete path toward realizing a radar that is significantly smaller and has higher resolution than the millimeter-wave radars that have been rapidly spreading in recent years, particularly for automotive applications.
The research group also demonstrated that the developed radar can be used to perform non-contact measurements of heartbeat movements on a person's chest through clothing, capturing detailed movements synchronized with an electrocardiogram. This opens up the possibility of conducting health checks quickly and easily, while also alleviating concerns about hygiene and privacy.
This research was conducted as part of the Ministry of Internal Affairs and Communications' Strategic Information and Communications R&D Promotion Programme (SCOPE) (165103002) and the Japan Science and Technology Agency's Precursory Research for Embryonic Science and Technology (PRESTO) (JPMJPR18J9). The results were published in the British scientific journal Nature Electronics on January 27, 2020 (UK time).
Please see below for the full press release.