Osamu Hashimoto

Aoyama Gakuin University, Edo, Tōkyō, Japan

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Publications (227)61.86 Total impact

  • K Sasaki · Y Isimura · K Fujii · K Wake · S Watanabe · M Kojima · R Suga · O Hashimoto
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    ABSTRACT: Measurement of the dielectric properties of ocular tissues up to 110 GHz was performed by the coaxial probe method. A coaxial sensor was fabricated to allow the measurement of small amounts of biological tissues. Four-standard calibration was applied in the dielectric property measurement to obtain more accurate data than that obtained with conventional three-standard calibration, especially at high frequencies. Novel data of the dielectric properties of several ocular tissues are presented and compared with data from the de facto database.
    No preview · Article · Aug 2015 · Physics in Medicine and Biology
  • Shinya KITAGAWA · Ryosuke SUGA · Kiyomichi ARAKI · Osamu HASHIMOTO
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    ABSTRACT: Vertical- and horizontal-polarization RCS of a dipole antenna was reduced using a switchable reflector. The switchable reflector can switch reflection level for the vertical-polarization and have absorption for the horizontal-polarization. The reflection level of the reflector for the vertical-polarization can be switched using pin diodes and the reflection for the horizontal-polarization can be reduced using resistor on the surface. The switchable reflector was designed to operate at 9 GHz and fabricated. The vertical-polarized reflection coefficient was switched -28 dB with OFF-state diodes and -0.7 dB with ON-state diodes, and horizontal-polarized one was less than -18 dB at 9 GHz. The reflector with ON-state diodes was applied to an antenna reflector of a dipole antenna and comparable radiation pattern to that with a metal reflector was obtained at 9 GHz. Moreover the reflector with OFF-state diodes was applied to the reflector of the dipole antenna and the RCS of the dipole antenna was reduced 18 dB for the vertical-polarization and 16 dB for the horizontal-polarization. Therefore the designed switchable reflector can contribute to antenna RCS reduction for dual-polarization at the operating frequency without degrading antenna performance.
    No preview · Article · Jul 2015 · IEICE Transactions on Electronics
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    ABSTRACT: Using our improved Optical Electric Field Sensor (OEFS) that incorporates our Log-Periodic Dipole Antenna Array (LPDA-type), it is now possible to accurately measure Electromagnetic Field Interference (Hidaka et al., IEICE Trans Commun (2014) 253–262). However, accurately evaluating the sensitivity characteristics of the LPDA-type OEFS via a standard electromagnetic field simulator resulted in an excellent but less than perfect outcome (Hidaka et al., IEICE Trans Commun (2014) 253–262). In this article, we show that a more accurate and reliable method of assessing the sensitivity characteristics of the OEFS via our software can be achieved using a detailed simulation model that prevents large errors. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1386–1390, 2015
    No preview · Article · Jun 2015 · Microwave and Optical Technology Letters
  • M. Nagasawa · Y. Kurosawa · R. Suga · O. Hashimoto · T. Yasuzumi · Y. Hasegawa
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    ABSTRACT: In this paper, a log-periodic dipole antenna array (LPDA) was downsized by using chip inductors and dielectric substrate for outdoor measurement. It was found that the directivity of a dipole antenna was decreased with increase of the shortening ratio of the element. A three-element LPDA was designed using the downsized dipole element. The reflection characteristics of the fabricated LPDA met the target value between 282 MHz - 385 MHz. The fabricated LPDA had about half length compared with that of original one, and the flat gain of from -0.46 to 1.89 dBi were obtained.
    No preview · Article · Mar 2015
  • S. Kitagawa · R. Suga · O. Hashimoto
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    ABSTRACT: Antenna design for radar cross section (RCS) reduction using reradiation interference cancellation was demonstrated. The RCS of a dipole antenna with a reflector was reduced using the interference cancellation between scattering and reradiation. The length of the feed line and element of the dipole antenna was designed for low return loss and RCS at 9 GHz. The optimized lengths of them are needed for the characteristics. The return loss of the fabricated dipole antenna was -25 dB and RCS of that with open termination was -40 dBsm which was reduced 15 dB compared to that with load termination.
    No preview · Article · Mar 2015
  • S. Kitagawa · R. Suga · K. Araki · O. Hashimoto
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    ABSTRACT: A switchable reflector which can switch reflection level using pin diodes for the vertical polarization and absorb for the horizontal polarization was proposed. The vertical polarized reflection coefficient was switched-29 dB with OFF-state diodes and-0.5 dB with ON-state diodes, and horizontal polarized one was less than-15 dB at 9 GHz. The reflector with ON-state diodes was applied to an antenna reflector of a dipole antenna and comparable radiation pattern to that with a metal reflector was obtained at 9 GHz. Therefore it can contribute to dual-polarized antenna RCS reduction at operating frequency without degrading antenna performance.
    No preview · Article · Feb 2015
  • Shinya Kitagawa · Ryosuke Suga · Osamu Hashimoto
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    ABSTRACT: A switchable microwave reflector, reflection of which is actively controlled using diodes was proposed. Pin diodes have large resistance and capacitance without DC bias and small resistance and inductance with DC bias in microwave band. The reflector was designed by using the characteristics. In this paper, effects of a periodic structure on the reflector were verified with simulation and equivalent circuit model. A prototype reflector was able to switch between about -20 dB and -0:1 dB reflection coefficient at 2 GHz. Copyright © 2014 The Institute of Electronics, Information and Communication Engineers.
    No preview · Article · Jul 2014 · IEICE Transactions on Electronics
  • Shinya Kitagawa · Ryosuke Suga · Osamu Hashimoto
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    ABSTRACT: A switchable reflector using pin diodes for the radar cross section (RCS) reduction of an antenna reflector was proposed. The reflection coefficient of the proposed reflector was able to be switched between less than -20 dB with OFF-state diodes and more than -0.8 dB with ON-state diodes around 9 GHz. The proposed reflector with ON-state diodes was applied to the reflector of a dipole array antenna and equivalent radiation pattern to one with a metal reflector was obtained. Moreover, it with OFF-state diodes reduces the antenna RCS more than 10 dB at 9 GHz. Therefore it can contribute to the antenna RCS reduction at the radiation frequency without degrading antenna performance.
    No preview · Conference Paper · Jun 2014
  • Shinya Kitagawa · Ryosuke Suga · Osamu Hashimoto
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    ABSTRACT: A switchable reflector using pin diodes for the radar cross section (RCS) reduction of an antenna reflector was proposed. The reflection coefficient of the proposed reflector was able to be switched between less than -25 dB with OFF-state diodes and more than -0.8 dB with ON-state diodes around 5 GHz. The proposed reflector with ON-state diodes was applied to a dipole antenna reflector and gave equivalent radiation pattern to with a metal reflector. It can contribute to the antenna RCS reduction at the radiation frequency without degrading antenna performance.
    No preview · Conference Paper · May 2014
  • K. Kakizaki · R. Suga · Y. Matsuda · Y. Matsushita · O. Hashimoto
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    ABSTRACT: In this paper, an antenna was proposed to cover the communication area of Multi-lane free-flow electric toll collection (MLFF-ETC) with only one frequency band and to prevent communication error due to shadowings. A microstrip antenna as a radiation element antenna for the antenna was designed at operating frequency of 5.8 GHz. The elements number and spacing were optimized for the transverse and traveling directions, and the power distribution illuminated by the designed two-dimensional-arrayed MLFF-ETC antenna was simulated.
    No preview · Article · Jan 2014
  • K Sasaki · H Segawa · M Mizuno · K Wake · S Watanabe · O Hashimoto
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    ABSTRACT: The free space method using a pair of lens antennas was modified for the complex permittivity measurement of biological samples from 20 to 110 GHz. Two methodologies were used to obtain the complex permittivities by the free space method, which were based on the reflection and transmission coefficients. The measurement results obtained with the two methodologies were compared with each other. The measured complex permittivities of the biological samples from the free space method were then compared with those measured using the coaxial probe method. Finally, the measurement data were also compared with those from measurement methods developed in past literatures.
    No preview · Article · Mar 2013 · Physics in Medicine and Biology
  • T. Suzuki · R. Suga · O. Hashimoto
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    ABSTRACT: In this paper, the transmission and leakage loss of post-wall waveguide depending on the thickness of porous substrate was evaluated. The transmission loss for various thickness of the porous waveguide was simulated in millimeter-wave band by using EM simulator. The valid substrate thickness for improving transmission loss by air-holes was studied. The leakage of the waveguide was also evaluated as a function of substrate thickness, and the relationship between transmission loss and leakage was discussed.
    No preview · Conference Paper · Jan 2013
  • H. Onoue · N. Kamiya · R. Suga · O. Hashimoto
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    ABSTRACT: This paper presents a broadband metal-plate lens with a short focal length by considering radiated electric field near a primary radiator. The gain and radiation pattern of the proposed lens antenna was measured to be equivalent characteristics of a conventional lens antenna. As a result, the proposed lens can be moved 35 cm to the primary radiator compared with the conventional lens. Moreover, the gain of the proposed lens antenna is simulated to be higher than 20 dBi up to 10 GHz.
    No preview · Conference Paper · Jan 2013
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    ABSTRACT: This paper presents a new simple method for reducing mutual coupling between dual-element microstrip antennas (MSAs) for bistatic radar using a wave absorber. The two elements are closely placed on a substrate by the distance of λ0/4 through the wall-shaped absorber. The height and width of the absorber were optimized for minimum mutual coupling with the electromagnetic simulator. It was found that less than -60 dB minimum mutual coupling can be achieved by the impedance matching of the absorber in a near field. The influence for the reflection characteristics from the absorber is small enough, and the reduction of the antenna gain is only 1.1 dB. The rate of the lost power characteristics showed that the absorption improves the mutual couplings. Then the proposed structure for a practical configuration was investigated. The measurement results of the optimized structure tallied well with the simulation results. Copyright © 2013 The Institute of Electronics, Information and Communication Engineers.
    No preview · Article · Jan 2013 · IEICE Transactions on Electronics
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    ABSTRACT: Most of fundamental biological tissues and organs, such as skin, muscle, and brain, are wet and solid. Water evaporation on the sample surfaces generally deteriorates the measurement of complex permittivities, especially in quasi-millimeter wave and millimeter wave bands. This letter, therefore, introduces a new sample preparation procedure for avoiding the water-evaporation effect. This method is first validated with liquid biological tissue, i.e., whole blood, and then applied to a wet and solid biological tissue, i.e., crystalline lenses. The results show that the new method enables reproducible measurements of the complex permittivities of wet and solid biological samples.
    Full-text · Article · Dec 2012 · IEEE Transactions on Electromagnetic Compatibility
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    ABSTRACT: A new wideband wave absorber with translucent structure using carbon fibers is presented in this paper. The absorber is composed of bundled short carbon fibers which are arranged in front of a back metal and a spacer. Absorption characteristics of the one-layered absorber showed that matching frequencies can be controlled by the thickness of the spacer and the length of the carbon fibers. To further improve the characteristics, multi-layered absorbers are designed with the same procedure as one-layered absorber. The designed absorber showed 15 dB absorption characteristics from 1.0 to 10.0 GHz. Then a small anechoic chamber with the inside dimension of 200 cm x 200 cm x 200 cm was fabricated using ninety-six proposed absorbers. The electrical power in the chamber was measured at 2.45 GHz and the results showed that the variation of the power was less than 4 dB inside a circle with radius of 60 cm as work space for electromagnetic measurements.
    No preview · Article · Dec 2012 · IEICE Transactions on Communications
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    ABSTRACT: This paper presents a compact metal plate lens antenna for evaluating a wave absorber placed on ceiling of the ETC gate. The focal distance of the lens was derived to be 129cm by the geometrical optics procedure. By arranging the lens in front of a horn antenna, the gain and beamwidth characteristics were improved from 18dBi to 26dBi and from 22 degrees to 7 degrees, respectively. Then the antenna characteristics were evaluated when the distance between the antenna and the lens was changed in order to miniaturize the lens antenna. As the result, the changes in beamwidth were held to within 1dB when the lens came close to the horn antenna. Scattering, phase and electric field intensity of electromagnetic wave were evaluated to clarify the foundation of the given characteristics. It was found that the field intensity for the miniaturized lens antenna is stronger than that for GO designed one though the phase uniformity is worse. The distance between the horn antenna and lens can be reduced to 80cm. The absorption characteristics for the arranged absorbers which have different absorptions were measured, and it was shown that the proposed method was suitable for specifying the deteriorated absorber in the ETC system.
    No preview · Article · Oct 2012 · IEICE Transactions on Communications
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    ABSTRACT: A can swells due to gas produced from an inner food caused by poor hermetic sealing of the can. This paper presents a measurement for the bottom shape to detect a swelled can by using the millimeter-wave imaging. For get higher spatial resolution and an adjustable focal distance, two collimated beam lenses were applied to the measurement system. First, a configuration of the system was studied with the electrical field intensity and focal distance by using full wave electromagnetic simulation. Next, the bottom shapes of cans with different pressure were evaluated quantitatively using the system. A shape change of 0.5mm was detected with pressure difference of 50kPa, and it is reasonable considering actual dimension of the can shape. A potential of the proposed detection method was presented.
    No preview · Article · Oct 2012 · IEICE Transactions on Electronics
  • A. Tsuchiya · H. Sugama · T. Sunamoto · N. Hidaka · O. Hashimoto
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    ABSTRACT: Proposed are low-loss and high-speed transmission flexible printed circuits (FPCs) based on liquid crystal polymer (LCP) films. The transmission losses of FPC based on LCP and polyimide (PI) film were measured under various conditions. At 23°C with 60 %RH, the differential-mode loss of differential line based on LCP films was 0.52 dB/cm lower than that of the differential line based on PI films at 40 GHz. Moreover, the differences in the loss of LCP film, caused by changes in temperature and relative humidity, were smaller than those of the PI film. These results show that the transmission characteristics of the FPCs based on LCP films were more stable and lower than those of the FPCs based on PI films.
    No preview · Article · Sep 2012 · Electronics Letters
  • A. Tsuchiya · H. Sugama · N. Hidaka · K. Miyamoto · S. Tsujino · O. Hashimoto
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    ABSTRACT: The relative complex permittivities of dielectric substrates for flexible printed circuits (FPCs) at 10 GHz were measured by the perturbation method using a cylindrical cavity resonator for temperatures ranging from 27 to 100 C. The temperature dependencies of the εγ and tan δ values of polyimide (PI) substrates were greatly changed by the moisture absorption properties. The ετ and tan δ of a liquid crystal polymer (LCP) substrate were not affected by temperature and were lower than those of the PI substrate below 70 °C. The temperature dependencies of the dielectric losses of microstrip lines (MSLs) for FPCs were evaluated. These losses were found to be more stable and lower for an LCP substrate than for a PI substrate.
    No preview · Article · Jul 2012 · Electronics Letters

Publication Stats

486 Citations
61.86 Total Impact Points

Institutions

  • 1993-2015
    • Aoyama Gakuin University
      • • Department of Electrical Engineering and Electronics
      • • College of Science and Engineering
      • • Graduate School of Science and Engineering
      Edo, Tōkyō, Japan
  • 2001-2004
    • Universität Stuttgart
      • Institute of Radio Frequency Technology
      Stuttgart, Baden-Württemberg, Germany
  • 2003
    • Yokohama Rubber Co. Ltd.
      Yokohama, Kanagawa, Japan