SASAKI Ai-ichiro

Department of Electronic Engineering and Computer ScienceAssociate Professor

Last Updated :2024/07/17

■Researcher basic information

Degree

  • Ph.D. in Electrical Engineering（2006/09 Tokyo Univ. of Science）
  • M.S. in Physics（1998/03 Univ. of Tokyo）

Homepage URL

Researcher number

20823610

ORCID ID

0000-0001-5869-6985

J-Global ID

Profile

  • Ai-ichiro Sasaki received the B.S. degree in applied physics from Tokyo University of Science in 1996, the M.S. degree in Physics from the University of Tokyo in 1998, and the Ph.D. degree in electrical engineering from Tokyo University of Science in 2006. From 1998 to 2018, he worked as a researcher with NTT Science and Core Technology Laboratory Group. He has been an associate professor at Kindai University since 2018. His research interests include electromagnetic technologies ranging from an LF band to optical wavelengths and their applications to intelligent sensing and communications.

Research Keyword

  • electromagnetics   machine learning   measurement   indoor positioning   wireless communications   body area network   

Research Field

  • Manufacturing technology (mechanical, electrical/electronic, chemical engineering) / Communication and network engineering
  • Manufacturing technology (mechanical, electrical/electronic, chemical engineering) / Measurement engineering

■Career

Career

  • 2018/04 - Today  Kindai UniversityDepartment of Electronic Engineering and Computer Science, Faculty of EngineeringAssociate Professor
  • 1998/04 - 2018/03  NTT CorporationScience and Core Technology Laboratory Group

Educational Background

  • 1996/04 - 1998/03  The University of Tokyo  Graduate School of Arts and Sciences  Department of Physics
  • 1992/04 - 1996/03  Tokyo University of Science  Faculty of Science  Department of Applied Physics

Member History

  • 2024/06 - Today   Member of IEICE Technical Committee on Electromagnetic Compatibility (EMCJ)
  • 2023/06 - Today   Editor of IEICE Transactions on Communications (JPN)
  • 2021/07 - Today   広島県EMC研究会 理事
  • 2022/04 -2024/03   Chair of technical committee on Photonics-applied Electromagnetic Measurement in IEICE Communications Society
  • 2023/07 -2023/12   Technical Advisor of 2023 IEICE International Conference on Emerging Technologies for Communications (ICETC 2023)
  • 2023/03 -2023/11   Chair of 5th International Workshop on Photonics applied to Electromagnetic Measurement (PEM2023)
  • 2022/06 -2023/08   Special Issue Editor of Future Internet
  • 2022/02 -2023/02   Special Section Editor of IEICE Transactions on Communications
  • 2022/07 -2022/12   Technical Advisor of 2022 IEICE International Conference on Emerging Technologies for Communications (ICETC 2022)
  • 2020/04 -2022/03   電気学会 学会活動推進員
  • 2020/04 -2022/03   Vice Chair of technical committee on Photonics-applied Electromagnetic Measurement in IEICE Communications Society
  • 2020/07 -2021/06   広島県EMC研究会 顧問
  • 2018/04 -2020/03   Secretary of technical committee on Photonics-applied Electromagnetic Measurement in IEICE Communications Society
  • 2016/06 -2018/03   Assistant secretary of technical committee on Photonics-applied Electromagnetic Measurement in IEICE Communications Society
  • 2015/06 -2017/05   Director of Publication Activities Council of IEICE Electronics Society
  • 2013/06 -2015/05   Editor of IEICE Electronics Express (ELEX)

■Research activity information

Paper

  • Improvement of prediction accuracy of magnetic field-based positioning with a high-isolation relay circuit
    Kouga Miyaji; Ai-ichiro Sasaki
    Proc. 5th International Workshop on Photonics applied to Electromagnetic Measurement (PEM2023) T-4 51 - 54 2023/11 [Refereed]
    ダウンロード
  • Machine-learning approach to short-range sensing and communications with reactive near fields
    Ai-ichiro Sasaki
    Workshop on Advances in Photonics 2023/08 [Invited]
  • Ai-ichiro Sasaki; Akinori Ban
    IEEE Trans. Instrum. Meas. Institute of Electrical and Electronics Engineers (IEEE) 71 2519314  0018-9456 2022/09 [Refereed]
  • Ai-ichiro Sasaki
    3rd Int. Congr. AI & Machine Learning 2022/08 [Refereed][Invited]
  • Ai-ichiro Sasaki; Ken Fukushima
    IEICE Trans. Fundamentals Institute of Electronics, Information and Communications Engineers (IEICE) E105-A (6) 994 - 1005 0916-8508 2022/06 [Refereed]
  • Ai-ichiro Sasaki
    Sensors MDPI AG 22 (6) 2240  2022/03 [Refereed]
     
    Recently, indoor localization has become an active area of research. Although there are various approaches to indoor localization, methods that utilize artificially generated magnetic fields from a target device are considered to be the best in terms of localization accuracy under non-line-of-sight conditions. In magnetic field-based localization, the target position must be calculated based on the magnetic field information detected by multiple sensors. The calculation process is equivalent to solving a nonlinear inverse problem. Recently, a machine-learning approach has been proposed to solve the inverse problem. Reportedly, adopting the k-nearest neighbor algorithm (k-NN) enabled the machine-learning approach to achieve fairly good performance in terms of both localization accuracy and computational speed. Moreover, it has been suggested that the localization accuracy can be further improved by adopting artificial neural networks (ANNs) instead of k-NN. However, the effectiveness of ANNs has not yet been demonstrated. In this study, we thoroughly investigated the effectiveness of ANNs for solving the inverse problem of magnetic field-based localization in comparison with k-NN. We demonstrate that despite taking longer to train, ANNs are superior to k-NN in terms of localization accuracy. The k-NN is still valid for predicting fairly accurate target positions within limited training times.
    ダウンロード
  • Ai-ichiro Sasaki; Akinori Ban
    Proc. 2021 Int. Conf. Emerg. Technol. Commun. (ICETC2021) A1-1 1 - 4 2021/12 [Refereed]
  • Binary classification of uplink-channel states for secure body-coupled communication
    Akinori Ban; Ai-ichiro Sasaki
    Proc. 4th International Workshop on Photonics applied to Electromagnetic Measurements (PEM2021) T-9 71 - 74 2021/11 [Refereed]
  • Ai-ichiro Sasaki; Kazuki Morita; Akinori Ban
    Proc. 2020 Int. Conf. Emerg. Technol. Commun. (ICETC2020) B2-4 1 - 4 2020/12 [Refereed]
  • Study of optical sensing technologies in evaluating short-range wireless systems with quasistatic fields
    Ai-ichiro Sasaki
    Tech. Dig. Int. Symp. Imaging, Sensing, Opt. Memory 2020 (ISOM'20) Mo-B-01 27 - 28 2020/11 [Refereed][Invited]
  • Ai-ichiro Sasaki; Eisuke Ohta
    IEEE Sensors J. Institute of Electrical and Electronics Engineers (IEEE) 20 (13) 7292 - 7302 1530-437X 2020/07 [Refereed]
  • Ai-ichiro Sasaki
    IEEE Trans. Magn. Institute of Electrical and Electronics Engineers (IEEE) 55 (12) 4004209  2019/12 [Refereed]
  • Ai-ichiro Sasaki; Junichi Kodate
    Proc. 2017 IEEE Conf. Antenna Meas. & Applicat. (2017 IEEE CAMA) Institute of Electrical and Electronics Engineers Inc. 72 - 75 2017/12 [Refereed]
     
    It is known that the attenuation rate of fields around multipoles becomes larger as the order of the multipoles increases. We experimentally confirmed that a magnetic quadru-pole and octapole composed of coil antennas can create low-frequency magnetic fields attenuating at the rate of 80 and 100 dB/decade, respectively. We also obtained approximate equations that represent the fields around the quadrupole and octapole in simple forms. The rapid attenuation of the low-frequency magnetic fields can provide identification areas with well-defined boundaries, which will be needed in order to build reliable radio-frequency identification systems for communication with things and mobile/wearable devices.
  • Ai-ichiro Sasaki; Akinori Furuya; Akihiko Hirata; Hiroki Morimura; Junichi Kodate
    Jpn. J. Appl. Phys. IOP PUBLISHING LTD 56 (9) 09NB01.1 - 09NB01.6 0021-4922 2017/09 [Refereed]
     
    A systematic design method is considered for maximizing the sensitivity of electrooptic sensors used for electric-field detection. The design method can be reduced to a routine procedure that includes matrix manipulation and differentiation. By applying the design method, the maximum sensitivity is realized with fewer optical components than in conventional electrooptic sensing systems. Since the proposed method shows a wide generality, it can be applied to designing sensors including various optical crystals. (C) 2017 The Japan Society of Applied Physics
  • Ai-ichiro Sasaki; Olivier Ouellette; Maxime Beaudry-Marchand; Akihiko Hirata; Hiroki Morimura
    IEEE Trans. Ind. Electron. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC 64 (4) 3216 - 3226 0278-0046 2017/04 [Refereed]
     
    We investigated the amplification of the magnetic field generated by a floating coil placed in resonance with a driving coil connected to a signal source. With this method, the magnetic field can be amplified without increasing power consumption of the signal source. From an equivalent-circuit model composed of the floating and driving coils, we derived useful formulae for maximizing the magnetic-field amplitude at an arbitrary target frequency. The validity of the formulae was experimentally demonstrated. It was found that under specific conditions, the current induced in the floating coil can be increased by more than one order of magnitude compared to the current in the driving coil, leading to amplification of the magnetic field that reaches 22 dB at the target frequency of 10 MHz without increasing power consumption. We also found that the floating coil is effective in suppressing undesirable magnetic field components originating from common-mode currents. These results pave the way to further reduction of the power consumption in wireless communication schemes such as near field communication.
  • Alignment of graded-index lens on silica-based PLC for sensor platform
    Kei Watanabe; Yu Kurata; Ai-ichiro Sasaki; Mikitaka Itoh
    Proc. 21st Microoptics Conf. 2016/10 [Refereed]
  • Design of polarization optics for electrooptic sensors
    Ai-ichiro Sasaki; Akinori Furuya; Akihiko Hirata; Hiroki Morimura
    Proc. Int. Symp. Opt. Memory 2016 (ISOM'16) 38 - 39 2016/10 [Refereed]
  • Akinori Furuya; Ai-ichiro Sasaki; Hiroki Morimura; Osamu Kagami; Takaya Tanabe
    Jpn. J. Appl. Phys. IOP PUBLISHING LTD 55 (9) 09SD01.1 - 09SD01.7 0021-4922 2016/09 [Refereed]
     
    The purpose of this study is to provide garnet films for volumetric magnetic holography. Volumetric magnetic holography usually employs an easily obtainable short-wavelength laser (visible light, not infrared light) with a large diffraction intensity. Bi-substituted garnet ferrite with a large Faraday rotation is promising for volumetric magnetic holography applications in the visible light region. However, a garnet film without a deteriorated layer must be obtained because a deteriorated layer (minute polycrystalline grains containing an amorphous phase) is formed during the initial deposition on a glass substrate. In particular, the required magnetooptical properties have not been obtained in a thin garnet film (100 nm or less) after annealing (1 h, 700 degrees C, oxygen atmosphere). Therefore, there is a need for excellent garnet films with the required magnetooptical (MO) properties even if the films are thin. By using a spinel ferrite buffer layer for garnet film deposition, we could obtain a thin garnet film with excellent MO properties. We determined the effect of the initial buffer layer on the crystallinity of the deposited garnet films by observing the film cross section. In addition, we undertook a qualitative estimation of the influence of the crystallinity and optical properties of the garnet film on a glass substrate with a spinel ferrite buffer layer. (C) 2016 The Japan Society of Applied Physics
  • Ai-ichiro Sasaki; Akihiko Hirata; Hiroki Morimura
    Proc. 2016 IEEE Antennas Propag. Soc. Int. Symp. IEEE 2016 (APSURSI) 409 - 410 1522-3965 2016 [Refereed]
     
    In magnetic-resonance wireless power transfer systems, a transmitter is equipped with a floating coil. We investigated the functions of the floating coil by analyzing an equivalent-circuit model of the transmitter. It is derived from the model that currents of the floating coil can be amplified without increasing the power consumption of the transmitter. As a result, strong magnetic fields can efficiently be generated with the floating coil. By solving the model, we obtain formulas for maximizing magnetic-field amplitude at an arbitrary frequency. The validity of our analysis is experimentally demonstrated.
  • Electric field measurement close to antennas at an upper frequency in the SHF band
    Kei Satoh; Teruo Onishi; Ai-ichiro Sasaki; Hiroki Morimura; Akihiko Hirata
    Proc. First PEM Int. Workshop in Kyoto (PEM2015) SC-3  2015/11 [Refereed]
  • Magneto-optical and crystalline properties of sputtered garnet ferrite film on spinel ferrite buffer layer
    Akinori Furuya; Ai-ichiro Sasaki; Hiroki Morimura; Osamu Kagamk; Takaya Tanabe
    Proc. Int. Symp. Opt. Memory 2015 (ISOM'15) 2015/10 [Refereed]
  • Akinori Furuya; Ai-ichiro Sasaki; Hiroki Morimura; Osamu Kagami; Takaya Tanabe
    Jpn. J. Appl. Phys. IOP PUBLISHING LTD 54 (9) 09MF02.1 - 09MF02.9 0021-4922 2015/09 [Refereed]
     
    The purpose of this study was to improve the optical characteristics of garnet ferrite films sputter-deposited on a glass substrate. The magnetooptical properties of the garnet ferrite film are strongly influenced by the thermal stress imposed on the substrate during crystallization. The condition of the interface between the garnet film and the substrate during the initial film deposition affects the magnetooptical characteristics of the entire film. In particular, we revealed the effect of stress generated at the interface on the crystallinity of the deposited garnet films with a stress relaxation buffer layer by observing the film cross section and the film surface. In addition, we qualitatively estimated of the effect of cracking in the garnet film on a glass substrate. (C) 2015 The Japan Society of Applied Physics
  • Ai-ichiro Sasaki; Ryoichi Okuizumi; Tsutomu Mizota; Hiroki Morimura; Osamu Kagami
    Proc. 2014 Asia-Pacific Microw. Conf. (APMC) IEEE 967 - 970 2165-4743 2014/11 [Refereed]
     
    We propose the concept of area discrimination with magnetoquasistatic (MQS) fields. Unlike radio waves, MQS fields are valid for forming a clearly defined area whose radius is below about 1 meter. Such an area can be utilized for identification of persons with mobile terminals. Since an important characteristic required for the terminals is isotropy in receiving magnetic fields, we made an isotropic receiver equipped with a 3-axis loop antenna. It is experimentally demonstrated that the receiver possesses sufficient isotropy. With the isotropic receiver, we measured areas formed by MQS fields at 10 MHz and demonstrated that MQS fields are useful for forming a clearly defined area for identification of mobile terminals.
  • Akinori Furuya; Ai-ichiro Sasaki; Hiroki Morimura; Osamu Kagami; Mitsuru Shinagawa
    Opt. Rev. SpringerOpen 21 (5) 605 - 613 1349-9432 2014/10 [Refereed]
     
    In this paper, we describe how to obtain a low cost electrooptic (EO) sensor module for the mass production of near-field intrabody communication devices. In our previous study, we used a bulk cleavage technique to fabricate EO modulators without the need for any optical polishing or washing processes. In this study, we fabricated EO modulators as a miniaturized chip sensor without a base portion, and clarified the feasibility of assembling optical components by only a passive alignment technique with a compact housing.
  • Magneto-optical property dependence of sputtered garnet ferrite film on initial deposition condition of substrate
    Akinori Furuya; Ai-ichiro Sasaki; Hiroki Morimura; Osamu Kagami; Takaya Tanabe
    Proc. Int. Symp. Opt. Memory 2014 (ISOM'14) 2014/10 [Refereed]
  • Ai-ichiro Sasaki; Tsutomu Mizota; Hiroki Morimura; Seiji Yabe; Ryoji Kikuchi; Satoshi Suzuki; Ryouichi Matsumoto
    IEEE Trans. Antennas Propag. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC 62 (5) 2802 - 2812 0018-926X 2014/05 [Refereed]
     
    Many application systems of capacitively coupled personal area networks (CC-PANs) are installed in the vicinity of walls. We therefore investigated noisy-channel models of a CC-PAN in consideration of a wall and a noise-reduction mechanism (NRM). Equivalent circuits representing the proposed channel models can be reduced to a Wheatstone bridge. It is found from the model that the noise is suppressed when the Wheatstone bridge is balanced. In practical CC-PAN systems, such a balanced condition can be realized by tuning a variable capacitor introduced as the NRM. The validity of the noisy-channel models and NRM is experimentally demonstrated.
  • Takayuki Ogasawara; Ai-ichiro Sasaki; Koji Fujii; Hiroki Morimura
    IEEE Trans. Antennas Propag. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC 62 (2) 804 - 813 0018-926X 2014/02 [Refereed]
     
    This paper presents a method of human body communication that employs magnetic coupling. Since a human body acts as one component of a loop for creating the magnetic coupling, strong coupling occurs only when a person closes the loop. Thus, a person's natural bodily movement forms a communication channel. Here, the validation of the mechanism of channel formation and the robustness against surrounding environment were presented. First, the validity of the circuit model was demonstrated through measurement of the transfer function of the channel (channel loss) at frequencies up to 20 MHz. Second, the validity of the mechanism of channel formation was demonstrated. Comparing to opening the loop, closing was found to increase the transfer function by more than 30 dB at frequencies below 10 MHz. This strong channel formation verifies its mechanism. Finally, to investigate the influence of a nearby metal object on the transfer function, a metal object was placed on or near the experimental setup; but no significant degradation of the transfer function was observed. This demonstrates robustness against surrounding environment. These results suggest the possibility of communication by magnetic coupling with a human body as part of the communication channel.
  • Mitsuru Shinagawa; Ai-ichiro Sasaki; Akinori Furuya; Hiroki Morimura; Kimihisa Aihara
    Jpn. J. Appl. Phys. IOP PUBLISHING LTD 52 (9) 09LA03.1 - 09LA03.8 0021-4922 2013/09 [Refereed]
  • Akinori Furuya; Ai-ichiro Sasaki; Hiroki Morimura; Kimihisa Aihara; Mitsuru Shinagawa
    Jpn. J. Appl. Phys. IOP PUBLISHING LTD 52 (9) 09LA04.1 - 09LA04.6 0021-4922 2013/09 [Refereed]
     
    This paper describes how to obtain a low cost electro-optical (EO) sensor module for the mass production of near-field intra-body communication devices. In this study, we used a bulk cleavage technique to fabricate EO modulators without the need for any optical polishing or washing processes, and clarified the feasibility of assembling optical components using only a passive alignment technique with a compact housing. (c) 2013 The Japan Society of Applied Physics
  • EO sensor module fabrication for near-field intra-body communication
    Akinori Furuya; Ai-ichiro Sasaki; Hiroki Morimura; Osamu Kagami; Mitsuru Shinagawa
    Proc. Int. Symp. Opt. Memory 2013 (ISOM'13) 2013/08 [Refereed]
  • Shaping magnetic-field patterns with multiple current loops for short-range wireless link
    Ai-ichiro Sasaki; Takayuki Ogasawara; Koji Fujii; Hiroki Morimura; Osamu Kagami
    Proc. 6th Global Symp. Millimeter-Waves 2013 2013/04 [Refereed]
  • Ai-ichiro Sasaki; Takako Ishihara; Nobutaro Shibata; Ryusuke Kawano; Hiroki Morimura; Mitsuru Shinagawa
    IEEE Trans. Antennas Propag. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC 61 (1) 390 - 402 0018-926X 2013/01 [Refereed]
     
    We investigated a noisy-channel model for a capacitively coupled personal area network (CC-PAN) with megahertz-frequency signals. The new channel model describes the influence of a power line connected to transceivers. Using the model, we analyzed characteristics of a CC-PAN channel in detail. The signal-to-noise ratio (SNR) for the CC-PAN channel can be calculated from the model. It is also shown that the SNR can be enhanced by using a common-mode choke. We also give a physical interpretation of the mechanism of the SNR enhancement. Furthermore, we propose design guidelines to obtain a large-SNR CC-PAN system. The validity of our model and analyses are confirmed by experimental results.
  • EO sensor fabricated using a bulk cleavage technique and its characteristics for near-field intra-body communication
    Akinori Furuya; Ai-ichiro Sasaki; Hiroki Mofimura; Kimihisa Aihara; Mitsuru Shinagawa
    Proc. Int. Symp. Opt. Memory 2012 (ISOM'12) 2012/10 [Refereed]
  • Cost-effective electro-optic sensor module for intra-body communication using optical pickup technology
    Mirsuru Shinagawa; Ai-ichiro Sasaki; Akinori Furuya; Hiroki Morimura; Kimihisa Aihara
    Proc. Int. Symp. Opt. Memory 2012 (ISOM'12) 2012/10 [Refereed]
  • Takayuki Ogasawara; Ai-ichiro Sasaki; Koji Fujii; Makoto Yaita; Hiroki Morimura; Yousuke Fujino; Takafumi Fujita; Masashi Shimizu
    Proc. 2012 IEEE Antennas Propag. Soc. Int. Symp. (APSURSI) IEEE 2012 8 - 14 1522-3965 2012 [Refereed]
     
    This paper presents a circuit model of the communication channel via magneto quasi-static field for personal area network. To demonstrate the validity of the circuit model, we measured the frequency characteristics of the channel in the range from 100 kHz to 20 MHz. The measured data agree well with the calculated characteristics derived from the circuit model. We also extracted parameters of the model from measured data. The typical loss of the circuit is -62 dB at 10 MHz.
  • A. Sasaki; T. Ishihara; N. Shibata; R. Kawano; H. Morimura; M. Shinagawa
    Proc. 2011 IEEE-APS Topical Conf. Antennas Propag. Wireless Commun. (APWC'11) 351 - 354 2011/09 [Refereed]
     
    We propose a noisy-channel model for a capacitively-coupled personal-area network (PAN) with megahertz-frequency signals. The model describes the influence of power lines connected to transceivers. We analyzed the signal-to-noise ratio (SNR) for the PAN channel. It is derived from the model that the SNR can be enhanced by using a common-mode choke. We also found conditions for enhancing the SNR. The validity of the model and analysis are confirmed by experimental results. © 2011 IEEE.
  • Ai-ichiro Sasaki; Ryusuke Kawano; Takako Ishihara; Mitsuru Shinagawa
    NTT Tech. Rev. 8 (3) 2010/03
  • Ai-ichiro Sasaki; Akinori Furuya; Mitsuru Shinagawa
    IEICE Trans. Commun. Institute of Electronics, Information and Communication, Engineers, IEICE E93-B (1) 144 - 153 1745-1345 2010/01 [Refereed]
     
    We propose a novel short-range wireless communications technology that uses quasi-static electric fields; it enables data communication between devices separated by up to 10 cm via dielectric media at a speed of 10 Mbps. It is considered to be a secure wireless technology since communication area is restricted to below about 10 cm. To suppress electromagnetic radiation, we adopted a baseband transmission scheme in which the quasi-static electric field is directly modulated by 10BASE-T data signals. Since the spectra of the data signals are concentrated to below 20MHz, the amplitude of the electric field rapidly decreases outside the communication area. This contributes to enhancing security of the communications system. In this paper, we explain a basic principle of the short-range wireless communications technology. Since baseband data signals are carried by the quasi-static electric field, the quality of the communication is easily degraded by the existence of the earth ground. To isolate the communications system from the earth ground, we introduce a novel electro-optic sensor to receive the quasi-static electric field. With the electro-optic sensor, stable data communication is possible at 10Mbps via dielectric materials, such as a wooden table. Copyright © 2010 The Institute of Electronics, Information and Communication Engineers.
  • Ai-ichiro Sasaki; Akinori Furuya; Mitsuru Shinagawa
    Sens. Actuators A Phys. ELSEVIER SCIENCE SA 151 (1) 1 - 8 0924-4247 2009/04 [Refereed]
     
    We investigated the characteristics of electro-optic modulators composed of ZnTe and CdTe. Their modulation depths below 100 kHz depend both on wavelength and input light power. The characteristics are explained by considering both the photoconduction effect and the Schottky effect. To keep the modulation depth constant below 100 kHz, the wavelength of the light should be long enough to suppress the photoconcluction effect. Using the ZnTe electro-optic modulator, we developed a sensitive voltage sensor that has constant sensitivity from DC to 30 MHz. Clear electrocardiograms can be obtained with the sensor. (C) 2009 Elsevier B.V. All rights reserved,
  • Ai-ichiro Sasaki; Mitsuru Shinagawa; Katsuyuki Ochiai
    IEEE Trans. Instrum. Meas. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC 58 (2) 457 - 466 0018-9456 2009/02 [Refereed]
     
    We have investigated the basic principles of intrabody communication with a newly developed ridge-type electrooptic (EO) sensor. To intuitively understand the essence of intrabody communication, we introduced a simple model based on the fact that human body can approximately he considered as a conductor wrapped in an insulator. To demonstrate the propriety of the model., we measured the characteristics of communication systems including a human body using the EO sensor. The experimental results well agree with the predictions from the model. The new ridge-type EO sensor is shown to be superior to our previous EO sensor, both in sensitivity and in stability. With the ridge-type EO sensor, we succeeded in 10-Mb/s data transmission through the human body. Furthermore, we discussed the advantages of using the EO sensor for intrabody communication.
  • Ai-ichiro Sasaki; Mitsuru Shinagawa
    IEEE Trans. Instrum. Meas. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC 57 (5) 1005 - 1013 0018-9456 2008/05 [Refereed]
     
    We have developed a new handy electrooptic (EO) probe to measure signals whose frequency is lower than 100 MHz. A distinct feature of the new EO probe is a long metal rod attached to an EO modulator. Measurement sensitivity does not depend on geometrical structures of devices under test (DUTs) with our new EO probe, whereas it does depend on geometrical structures of DUTs with a conventional handy EO probe. The sensitivity is at least 18 dB higher than that of the conventional one. In this paper, we qualitatively explain the effects of the rod on sensitivity and show experimental results, which agree well with the explanation. The advantages of signal measurements with an EO probe are also discussed, and two applications, where an EO probe plays important and essential roles, are proposed.
  • Ai-ichiro Sasaki; Mitsuru Shinagawa
    Jpn. J. Appl. Phys. IOP PUBLISHING LTD 47 (2) 918 - 924 0021-4922 2008/02 [Refereed]
     
    We analyzed the polarization states of light propagating in an electro-optic (EO) crystal with static birefringence. The analysis is based on a model in which the crystal consists of thin layers with the electro-optic effect and thin layers with static birefringence in an alternating sequence. The Jones matrix that represents the crystal was derived from the model. We also calculated the Jones matrix representing an EO crystal with optical activity because optical activity is considered to be a kind of static birefringence. Using the Jones matrices, we analyzed the polarization states of light modulated through an EO crystal with residual static birefringence and that with optical activity. It was shown that the modulation depth is decreased both by residual static birefringence and by optical activity. We obtained conditions to minimize the drop of the modulation depth. We also experimentally investigated the modulation depth using CdTe and Bi12SiO20, which are EO crystals possessing residual static birefringence and optical activity, respectively. The experimental results agreed well with the calculated results. The obtained conditions which minimize the drop of the modulation depth are valid for designing sensitive sensors using various EO crystals.
  • Electro-optic sensor for intrabody communication and its application to MICT
    Ai-ichiro Sasaki; Katsuyuki Ochiai; Akinori Furuya; Mitsuru Shinagawa
    Proc. 2006 Int. Symp. Medical Inform. Commun. Technol. (ISMICT) B1-1  2006/12 [Refereed]
  • Ai-ichiro Sasaki
    Tokyo University of Science 2006/09 [Refereed]
    ダウンロード
  • Ai-ichiro Sasaki; Mitsuru Shinagawa; Katsuyuki Ochiai
    2004 IEEE LEOS Annu. Meet. Conf. Proc., vols. 1 & 2 IEEE 122 - 123 1092-8081 2004/11 [Refereed]
     
    We developed highly sensitive and stable electro-optic sensors for intrabody communication among mobile computers. We explain the principle of the communication and the advantage of detecting signals on human bodies with such sensors.
  • Hiroyoshi Togo; Ai-ichiro Sasaki; Akihiko Hirata; Tadao Nagatsuma
    Int. J. RF Microw. Computer-Aided Eng. WILEY-BLACKWELL 14 (3) 290 - 297 1096-4290 2004/04 [Refereed]
     
    This article describes an electric-field measurement system that is based on electro-optic sampling (EOS). This system is able to map near- and far-field patterns of millimeter waves radiated from antennas by scanning the electric-field sensor probe. With the bandwidth set to more than 150 GHz, it can detect an electric field of less than 1.0 V/m at 60 GHz. This electric field is about one-tenth the field limit detectable by conventional microwave EOS systems. A comparison of measured and calculated electric fields in both the frequency and time-domains demonstrates the accuracy and usefulness of the system. (C) 2004 Wiley Periodicals. Inc.
  • Tadao Nagatsuma; Hiroyoshi Togo; Koichi Narahara; Naofumi Shimizu; Ai-ichiro Sasaki
    2004 IEEE Int. Topical Meeting Microw. Photon., Tech. Dig. IEEE 20 - 23 2004 [Refereed][Invited]
     
    We review recent progress in optical techniques for radio-wave signal measurement in the frequency region from gigahertz to terahertz. This paper highlights a highly-sensitive electro-optic sensor material such as DAST, circuit diagnosis, antenna characterization, millimeter-wave and terahertz-wave imaging of objects.
  • H. Adachi; K. Nagaoka; F. Tsunesada; M. Yoshimura; Y. Mori; T. Sasaki; A. Sasaki; T. Nagatsuma; Y. Ochiai; N. Fukasaku
    IEICE Trans. Electron. E86-C (7) 1352 - 1358 0916-8516 2003/07 [Refereed]
  • Ai-ichiro Sasaki; Tadao Nagatsuma
    IEICE Trans. Electron. E86-C (7) 1345 - 1351 0916-8516 2003/07 [Refereed][Invited]
  • Electro-optic measurement using 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) crystal
    H. Adachi; K. Nagaoka; F. Tsunesada; T. Higo; M. Yoshimura; Y. Mori; T. Sasaki; A. Sasaki; T. Nagatsuma; Y. Ochiai; N. Fukasaku
    Proc. 7th Int. Conf. Organic Nonlinear Optics 2003/05 [Refereed]
  • H Ito; T Nagatsuma; A Hirata; T Minotani; A Sasaki; Y Hirota; T Ishibashi
    IEE Proc. Optoelectron. INST ENGINEERING TECHNOLOGY-IET 150 (2) 138 - 142 1350-2433 2003/04 [Refereed]
     
    The design and characterisation of a millimetre wave uni-travelling-carrier photodiode with a monolithically integrated matching (impedance transform) circuit utilising a coplanar-waveguide short stub are presented. The device with the matching circuit shows about 50% higher efficiency at 100 GHz than the one without it. The frequency response was characterised through time-domain measurement by means of an electro-optic sampling technique. The I dB down bandwidth of the device is as wide as 40 GHz, and the frequency response characteristics are in good agreement with circuit model calculations. The maximum saturation output power is 20.8 mW at 100 GHz for a bias voltage of -3 V, which is the highest output power ever generated directly from a photodiode in the W-band.
  • Electric-field imaging system using two- dimensional electro-optic sensor
    Ai-ichiro Sasaki; Nicholas Meisl; Tadao Nagatsuma
    Tech. Dig. 4th Korea-Japan Joint Workshop Microwave and Millimeter-Wave Photonics 77 - 80 2003/01 [Refereed]
  • H. Adachi; K. Nagaoka; F. Tsunesada; M. Yoshimura; Y. Mori; T. Sasaki; A. Sasaki; T. Nagatsuma; Y. Ochiai; N. Fukasaku
    Tech. Dig. 2002 International Topical Meeting on Microwave Photonics (MWP2002) Institute of Electrical and Electronics Engineers Inc. 85 - 88 2002/11 [Refereed]
     
    We present a new method called the slope nucleation method (SNM) for the growth of high-quality DAST crystals. Electro-optic (EO) measurement shows DAST crystals exhibits five-times sensitivity enhancement as compared to KTiOPO4 (KTP) crystals.
  • Ai-ichiro Sasaki; Tadao Nagatsuma
    Tech. Dig. 2002 International Topical Meeting on Microwave Photonics (MWP2002) Institute of Electrical and Electronics Engineers Inc. 81 - 84 2002/11 [Refereed]
     
    A novel electric-field scanner (E-Scan) allows us to obtain two-dimensional electric-field images in a short time by scanning with a laser beam. Measurement time with E-Scan is decreased by more than one order compared to previous electric-field mapping systems. We have demonstrated measurement of antenna radiation patterns and millimeter-wave imaging with E-Scan.
  • H Adachi; K Nagaoka; F Tsunesada; M Yoshimura; Y Mori; T Sasaki; A Sasaki; T Nagatsuma; Y Ochiai; N Fukasaku
    Jpn. J. Appl. Phys., pt. 2 INST PURE APPLIED PHYSICS 41 (10A) L1028 - L1030 0021-4922 2002/10 [Refereed]
     
    We evaluated the electro-optic (EO) properties of 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) crystals by external EO probing. The EO signal power obtained from the DAST crystal increased by 8 dB compared to that obtained from the KTiOPO4 (KTP) crystal at 90kHz. The larger EO signal power obtained from the DAST crystal was almost constant at low frequencies (30 Hz to 90 kHz), whereas the KTP crystal could not respond below 180 Hz. We also observed excellent signals at all measured points due to the high crystallinity of the crystal grown by the,lope nucleation method (SNM).
  • Millimeter-wave imaging using photonic techniques
    Ai-ichiro Sasaki; Tadao Nagatsuma
    NTT Rev. 14 (6) 32 - 41 2002/06
  • Tadao Nagatsuma; Nabil Sahri; Akihiko Hirata; Yakov Royter; Ai-ichiro Sasaki
    2002 IEEE MTT-S Int. Microw. Symp. Dig., vol1. 1-3 IEEE 1497 - 1500 0149-645X 2002 [Refereed]
     
    We report the active photonic probes which enable on-wafer measurements of electrical scattering parameters with a bandwidth exceeding 300 GHz. The probes employ a high-speed uni-traveling-carrier photodiode to optically generate the electrical stimulus and the electro-optic sampling technique to measure the electrical response signals. The probe modules are packaged using micro-optic technology and exhibit excellent optical characteristics. They are easy to use and enable reliable and reproducible measurements and should help to overcome the bandwidth-limitation of present all-electronic systems.
  • Ai-ichiro Sasaki; Tadao Nagatsuma
    Jpn. J. Appl. Phys. INST PURE APPLIED PHYSICS 41 (1AB) L83 - L86 0021-4922 2002/01 [Refereed]
     
    We present a novel reflection-type imaging system that uses 100-GHz cw millimeter waves (MMWs). In the system, MMWs reflected by objects are separated from an incident MMW path by a circulator. The separated MMWs are detected by a high-sensitivity electro-optic (EO) sensor mounted in a rectangular waveguide. With the EO sensor, minimum detectable MMW power is less than -60 dBm. Using cw-MMWs, we can obtain both amplitude and phase images of objects directly. The system also features high-speed mechanical stages, which reduce image acquisition time. The acquisition time for 20,000-pixel amplitude and phase images is less than 10 min. We demonstrate that reflection-type imaging is effective in providing important information that cannot be obtained by conventional transmission-type imaging.
  • Reflection-type 100-GHz millimeter-wave imaging using a photonic mixer
    Ai-ichiro Sasaki; Tadao Nagatsuma
    Tech Dig. 3rd Japan-Korea Joint Workshop Microwave and Millimeter-Wave Photonics 71 - 74 2002/01 [Refereed]
  • T. Nagatsuma; M. Shinagawa; N. Sahri; A. Sasaki; Y. Royter; A.Hirata
    IEEE Trans. Microw. Theory Techn. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC 49 (10) 1831 - 1839 0018-9480 2001/10 [Refereed][Invited]
     
    This paper reviews recent advances in 1.55-mum photonic systems for measurement and sensors covering the frequency range from microwaves to millimeter waves. We first deal with the basic technologies for photonic measurement, i.e., generation, transmission, and detection of high-frequency signals, and then discuss recent practical applications, including high-speed integrated-circuit probers, sampling oscilloscopes, network analyzers, and some free-space sensing systems.
  • T. Nagatsuma; T. Ishibashi; A. Hirata; Y. Hirota; T. Minotani; A. Sasaki; H. Ito
    Electron. Lett. 37 (20) 1246 - 1247 0013-5194 2001/09 [Refereed]
     
    A 100 GHz high-output power uni-travelling-carrier photodiode with a monolithically integrated matching circuit was designed and tested. The circuit consisted of a uni-travelling-carrier photodiode (UTC-PD). Two short planar waveguides and a metal-insulator, metal capacitor. The time domain and frequency domain characterstics of the device were measured by the EOS technique. The device exhibited a band operation with 3dB bandwidth of 50 GHz with output power at 100 GHz output power mW at 100 GHz.
  • Ai-ichiro Sasaki; Tadao Nagatsuma
    CLEO(R)/Pacific Rim 2001, vol. II, Tech. Dig. IEEE 2 740 - 741 2001/07 [Refereed]
     
    We present a novel reflection-type millimeter-wave (MMW) imaging system that uses photonic techniques. In the system, we use a MMW circulator and a highly sensitive waveguide-mounted electro-optic (EO) sensor to detect MMWs reflected by objects.
  • T. Minotani; Y. Royter; H. Ishii; A. Hirata; K. Machida; A. Sasaki; T. Nagatsuma
    2001 IEEE MTT-S Int. Microw. Symp. Dig. 57 - 60 0149-645X 2001/05 [Refereed]
  • Tadao Nagatsuma; Mitsuru Shinagawa; Ai-ichiro Sasaki
    NTT Rev. NTT CORP 12 (6) 55 - 58 0915-2334 2000/11 [Refereed]
     
    We are now living in an amazing "age of radio waves" and enjoying its many benefits. While a human being cannot feel the presence of radio waves with the five senses, radio waves can still be observed by a variety of measurement methods. Among these, technology for observing radio waves using light has recently become the focus of much attention. This article introduces this measurement technology and presents some examples of its application.
  • Ai-ichiro Sasaki; Tadao Nagatsuma
    IEEE J. Sel. Topics Quantum Electron. 6 (5) 735 - 740 1558-4542 2000/09 [Refereed]
  • 1.55-um photonic systems for measurement and sensors up to the submillimeter-wave region
    Nabil Sahri; Mitsuru Shinagawa; Ai-ichiro Sasaki; Tadao Nagatsuma
    Proc. Int. Topical Workshop Contemporary Photon. Technol. 2000 (CPT2000) 2000/01 [Refereed]
  • Y. Royter; T. Minotani; H. Ishii; A. Hirata; S. Yagi; K. Machida; T. Furuta; T. Ishibashi; A. Sasaki; T. Nagatsuma
    LEOS 2000 IEEE Annu. Meeting Conf. Proc., vols. 1 & 2 IEEE 283 - 284 1092-8081 2000 [Refereed]
  • Ai-ichiro Sasaki
    The University of Tokyo 1998/01 [Refereed]
    ダウンロード

MISC

Courses

  • Electromagnetic Wave EngineeringElectromagnetic Wave Engineering Kindai University
  • Artificial IntelligenceArtificial Intelligence Kindai University
  • Signal ProcessingSignal Processing Kindai University
  • Communications EngineeringCommunications Engineering Kindai University
  • Logic CircuitsLogic Circuits Kindai University
  • Vector AnalysisVector Analysis Kindai University
  • Electromagnetic Wave EngineeringElectromagnetic Wave Engineering Kanagawa Institute of Technology
  • Sensor TechnologySensor Technology Saitama University

Affiliated academic society

  • The Institute of Electrical Engineers of Japan   The Institute of Electronics, Information and Communication Engineers   The Japan Society of Applied Physics   The Physical Society of Japan   IEEE   

Research Themes

Industrial Property Rights