Our main research interest is in applied electromagnetic systems in lossy media such as seawater and simulated human body.

Research on Undersea Use of Radio Waves

  • It is said that the ocean is the second space, but there are only a few applications that use radio waves. Nowadays, the use of radio waves in the ocean is expected to contribute to the development of marine resources. Since ocean radio experiments are costly, we propose a pseudo-scale model that enables laboratory experiments and contributes to accelerating the use of radio waves in the ocean.
    • array on sea surface
    Underwater diver location
    pseudo_scale_model_measurement_system
    Measument system of
    pseudo-scale model

Research on Methods for Evaluating the Effects of Radio Waves on the Human Body

  • Specific Absorption Rate (SAR) is internationally defined as an index of biological effects of radio waves, and Ishii Laboratory has been conducting research on SAR evaluation techniques in collaboration with the National Institute of Information and Communications Technology (NICT) since 2004. Currently, we are studying calibration techniques for electric field probes for SAR measurement in order to extend SAR evaluation to frequencies from 6 GHz to 10 GHz.
probe calibration using robot arm
SAR probe calibration device
developed jointly with NICT
gain_measurement_in_pure_water
Gain measurement system of reference
antenna for 5G/B5G SAR probe calibration

Human Motion Analysis Using RFID System

  • RFID tags are tags with embedded ID information, and information about the tag can be exchanged via radio waves. Our goal is to classify human motions by irradiating RFID tags with weak radio waves and monitoring the received signal strength (RSSI) of the tags. Currently, we are attempting to classify simple movements such as raising and lowering arms and legs by incorporating methods such as time series analysis.
RSSI time series response
An example of time series response from an RFID tag
to upper and lower limb rotational motion

Research on a Simple Method for Measuring Small Antenna Efficiency

  • When a small antenna is surrounded by a metal shield without gaps, only the radiated power from the small antenna is suppressed. The method for measuring the radiation efficiency of small antennas based on this fact is known as the Wheeler method. However, it is known that the metal shielding can cause some drops in the radiation efficiency at discrete frequencies, and we are currently investigating a method to avoid these drops by using a rational function fitting.
Wheeler_method_principle
Principle of the Wheeler Method
(Radiation suppression
when a metal cap is covered)
estimated radiation efficiency after removing cavity resonances
Example of radiation efficiency
after cavity resonance removal
(Inverted-F antenna)