Achievement Award

Practical Realization and Development of High Performance Radio Wave Absorbers


  Research on radio wave absorbers started out as an avoidance technology from detection radar systems. Recently, wave absorbers are widely used for the safe, reliable and high efficient operation of social infrastructure such as mobile communications and electronic toll collection systems (hereinafter "ETC systems"), in addition to performance improvements for anechoic chambers for electromagnetic compatibility, the evaluation of antenna characteristics, and noise reductions in electronic devices. Prof. Hashimoto has been conducting research on such absorbers over the years, and absorbers that he has developed have contributed not only to electronics and communications, including ETC, wireless LAN, radar and near electromagnetic fields, but also to architectures (1)-(4).
  Prof. Hashimoto proposed multi-layered absorbers using resistive films, specially shaped absorbers optimized with electromagnetic simulations, and those realized by intense cooperation of dielectric and magnetic materials. The practical realization of these absorbers for ETC systems is his major accomplishment (5)-(8). Radio-wave absorbers are essential to suppress the reflected and interference waves from ETC gates, road surfaces and adjacent lanes. The standard-compliant performance are required for absorbers, and their environment resistance and manner of operations must also be considered. He developed ultra-thin absorbers contributing greatly to the prevailing of ETC systems where 3 billion cars pass through yearly. As an example, Figure 1 shows the absorber for suppressing interference waves from adjacent lanes. The large plate-like absorbers were needed for this application, and the lattice type was applied to resist high winds. On the other hand, a thin light-weight absorber is in high demanded for the ceilings of ETC gates. Prof. Hashimoto invented a high permittivity material using graphite which had been avoided for absorbers due to its anisotropic permittivity. The thin sheets including the graphite were laminated while rotating to obtain the isotropic high permittivity and the specific weight and thickness of the realized absorber are reduced to half and quarter with maintenance of its absorption property, respectively.
  Moreover, additional notable accomplishments by Prof. Hashimoto include the high precision measurement of high-permittivity material to realize high performance absorbers. The permittivity tensor estimation method for anisotropic materials was developed using high-precision reflection and transmission characteristics measured by using the developed system shown in Figure 2(9),(10). The systematization of high precision measurement appropriate to the purpose and frequency band is his remarkable contribution.
  In summary, these accomplishments are extraordinary, notable, and are utilized in a variety of fields such as architecture and traffic. They expand the academic framework of ICICE and he definitely deserves the IEICE Achievement Award.
Fig.1 Lattice type wave absorber for interference wave suppression between adjacent lanes.
Fig.1 Lattice type wave absorber for interference wave suppression between adjacent lanes.
Fig.2 Material constant measurement system applying dielectric lens antennas.
Fig.2 Material constant measurement system applying dielectric lens antennas.


  1. D. Kitahara, R. Suga, K. Araki, and O. Hashimoto, "Circular Patch Array Absorber Design for Oblique Incidence by Using Winding Ratio Model of Transformers," IEEE Trans. Electromagn. Compat., vol.61, no.1, pp.65-72, Feb. 2019.
  2. S. Kitagawa, R. Suga, and O. Hashimoto, gStudy on Microwave Relflection Reduction of X-Band Array Antenna Using Microwave Absorb/Reflect Switchable Reflectors,h IEICE Trans. C, Vol. J97-C, no. 12, Dec. 2014.
  3. T. Yasuzumi, N. Kamiya, R. Suga, O. Hashimoto, Y. Matsushita, and Y. Matsuda, "Miniaturization of parallel-plate lens antenna for evaluation of wave absorbers placed on ceiling of ETC gates," IEICE Trans. Commun., vol.E95-B, no.10, pp.3225-3231, Oct. 2012.
  4. O. Hashimoto supervisor, gDevelopment of Electromagnetic Wave Absorbers and Shielding Materials and Its Application,h CMC Publishing Co., 2016D
  5. T. Doi, O. Hashimoto, N. Tashiro, T. Inoue, and A. Fujita, gAn Experimental Study on Wave Absorbers Using Graphite and Modified Polyamide Resin for ETC Application,h IEICE Trans. BCvol.J90-BCno.8Cpp.761-763CAug. 2007.
  6. K. Matsumoto, M. Takimoto, O. Hashimoto, and M. Sakai, gA Study on Wave Absorbers with Periodic Lattices for Installing between ETC Lanes,h IEICE Trans. BCvol.J90-BCno.4Cpp.447-451CAprD2007.
  7. K. Matsumoto, A. Kitamoto, T. Nakamura, T. Aoyagi, O. Hashimoto, and T. Miyamoto, gWave Absorber Using Cylindrical Bars with Magnetic Loss Covers Arranged Metallic Mesh for Improving ETC EnvironmentChIEICE Trans. Electron., vol. E91-C, no. 2, Feb. 2008.
  8. K. Matsumoto, T. Ozawa, T. Nakamura, T. Aoyagi, O. Hashimoto, and T. Miyamoto, gWave Absorber Formed by Arranging Cylindrical Bars at Intervals for Installing between ETC LanesCh IEICE Trans. Electron., vol. E89-C, no. 11, Nov. 2006.
  9. K Sasaki, H Segawa, M Mizuno, K Wake, S Watanabe and O Hashimoto, gDevelopment of the complex permittivity measurement system for high-loss biological samples using the free space method in quasi-millimeter and millimeter wave bands,h Phys. Med. Biol. 58, 1625-1633, 2013.
  10. T. Sakai, O. Hashimoto, gMeasurement Method for Complex Permittivity Tensor Based on Free-Space Transmission Method Using Focusing Lens in Millimeter-wave Band,h IEICE Trans. C, vol.J90-C, no.3, pp.235-237, Mar. 2007.