Masaharu Takahashi

Chiba University, Tiba, Chiba, Japan

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Publications (55)28.13 Total impact

  • Ho-Yu Lin, Masaharu Takahashi, Kazuyuki Saito, Koichi Ito
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    ABSTRACT: An in-body wireless communication system has attracted increasing attention because it can replace the connectivity of biological telemetry monitoring. However, the human body is a very complex environment (lossy, dispersive, and inhomogeneous) and affects the electromagnetic (EM) wave in the near field. Moreover, the entire human geometry affects the radiation pattern in the far field. This communication presents the behavior of the EM wave in the near and far fields at 2.45 GHz when a dipole antenna (used as an implantable antenna) is embedded in the vicinity of the clavicle, upper arm, lower arm, and hand of a human body. The effect on the electric field and radiation performance is simulated by the finite-difference time-domain method. By introducing a three-layered phantom, the antenna performance is confirmed. Moreover, the measured and simulated results are in good agreement with each other. The information derived from this study can be used in the evaluation of the link budget of in-body wireless communication.
    IEEE Antennas and Propagation Magazine 10/2013; 61(10):5350-5354. · 1.18 Impact Factor
  • Nozomi Haga, Kazuyuki Saito, Masaharu Takahashi, Koichi Ito
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    ABSTRACT: The physical channels establishing intrabody communications were first treated as capacitive circuits by Zimmerman. In Zimmerman's model, the human body is approximated as a perfect conductor. The equivalent-circuit parameters of the perfect conductor models can be strictly obtained based on electrostatic analyses; however, the perfect conductor models cannot be applied if conduction currents inside the human body are not negligible. In the present paper, a theory of the equivalent circuit for lossy conductors is described, and the physical mechanism of the communication channels inducing conduction currents inside the human body is addressed.
    IEEE Transactions on Antennas and Propagation 05/2013; 61(5):2807-2816. · 2.33 Impact Factor
  • Ho-Yu Lin, Masaharu Takahashi, Kazuyuki Saito, Koichi Ito
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    ABSTRACT: Implantable devices have been continually anticipated as a future tool for in-body wireless communication because of their potential to replace cable connectivity with biological telemetry monitoring. This paper presents an implanted compact folded antenna of 20.3 mm × 0.8 mm × 0.8 mm that is designed to operate at one of the UHF bands (0.951-0.956 GHz). The measurement is implemented with an equivalent human phantom such as layered phantom representing the human arm. When the proposed antenna is implanted into a human arm, it has a maximum antenna gain of -23.5 dBi and wireless communication is viable because the margin exceeds 20 dB, according to link budget calculations.
    IEEE Transactions on Antennas and Propagation 03/2013; 61(3):1363-1370. · 2.33 Impact Factor
  • Kazuyuki Saito, Mizuki Inoue, Masaharu Takahashi, Koichi Ito
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    ABSTRACT: In recent years, various types of medical applications of microwaves have widely been investigated and reported. In this paper, biological tissue coagulation device, which use the thermal effect of microwave, is introduced. In addition, characteristics of the device are evaluated by numerical calculations and experiments. As a result of investigations, possibilities of surgical treatment by developed device could be confirmed.
    Electromagnetic Theory (EMTS), Proceedings of 2013 URSI International Symposium on; 01/2013
  • Chia-Hsien Lin, Kazuyuki Saito, Masaharu Takahashi, Koichi Ito
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    ABSTRACT: Body-centric wireless communications (BCWCs) have received a great deal of attention recently. This communication proposes a compact planar inverted-F antenna (PIFA) operating at 2.45 GHz for on-body communications. Two shorting structures and a folded ground plane are used to improve the impedance matching and decrease the size of the proposed antenna. As a result, the proposed antenna is low-profile and compact in size, and it does not change significantly when in close proximity to the human body. This communication studies the characteristics of the proposed antenna close to the arm phantom by simulation and experiments. Both simulated and measured results are in good agreement.
    IEEE Transactions on Antennas and Propagation 09/2012; 60(9):4422-4426. · 2.33 Impact Factor
  • Zhengyi Li, Kazuyuki Saito, Masaharu Takahashi, Koichi Ito
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    ABSTRACT: Small Wearable Antenna with Folded Ground for Body-Centric Wireless Communications
    IEICE Transactions. 01/2012; 95-B:109-112.
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    ABSTRACT: Mutual coupling is a critical problem in the design of MIMO antennas because it deteriorates the performance of MIMO systems, which not only affects the antenna efficiency but also influences the correlation. Therefore, in this paper, using parasitic elements to reduce mutual coupling is studied. By adding parasitic elements a double-coupling path is introduced and it can create a reverse coupling to reduce mutual coupling. As an example, a dual-slot-element antenna with parasitic monopoles for mobile terminals is described. The discussion on channel capacity shows that the antenna can be considered as a good candidate for MIMO systems. Furthermore, based on the study of current distributions, it is concluded that the technique is sensitive to relative positions between parasitic elements, and relative positions between active element and parasitic element. Finally, we also extend the technique to a tri-element antenna.
    IEEE Transactions on Antennas and Propagation 01/2012; 60(2):473-481. · 2.33 Impact Factor
  • Koichi Ito, Nozomi Haga, Masaharu Takahashi, Kazuyuki Saito
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    ABSTRACT: In recent years, body-centric wireless communications have been studied because they have potential to improve the qualities of various kinds of applications. Since the prospective frequencies for the body-centric wireless communications are in an extremely wide range from megahertz to gigahertz, an objective idea on how to select a right frequency band for individual applications is required. However, few publications have tackled this need. In this paper, the frequency dependence of the communication channels in the range of 3 MHz to 3 GHz is assessed based on numerical analyses.
    Proceedings of the IEEE 01/2012; 100(7):2356-2363. · 6.91 Impact Factor
  • Nozomi Haga, Kazuyuki Saito, Masaharu Takahashi, Koichi Ito
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    ABSTRACT: Proper Derivation of Equivalent-Circuit Expressions of Intra-Body Communication Channels Using Quasi-Static Field
    IEICE Transactions. 01/2012; 95-B:51-59.
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    ABSTRACT: Although the effect of electromagnetic interference on an implanted cardiac pacemaker due to a nearby mobile phone has been investigated, there have been few studies on the enhancement of the specific absorption rate (SAR) around an implanted cardiac pacemaker due to a nearby mobile phone. In this study, the SAR distribution around a pacemaker model embedded in a parallelepiped torso phantom when a mobile phone was nearby was numerically calculated and experimentally measured. The results of both investigations showed a characteristic SAR distribution. The system presented can be used to estimate the effects of electromagnetic interference on implanted electric circuits and thus could lead to the development of guidelines for the safe use of mobile radio terminals near people with medical implants.
    IEICE Transactions on Communications. 01/2012; E95.B(6):2129-2132.
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    ABSTRACT: Recently, electromagnetic interference (EMI) of an implanted pacemaker with a mobile phone has been investigated. However, there are few studies of specific absorption rate (SAR) around the implanted pacemaker by the mobile phone. In this study, SAR distribution around the pacemaker model embedded into the parallelepiped torso phantom was evaluated experimentally. As a result, characteristic SAR distribution, which is caused by implanted pacemaker, was observed.
    10/2011;
  • Hiroshi Itakura, Kazuyuki Saito, Masaharu Takahashi, Koichi Ito
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    ABSTRACT: Microwave thermal therapy is one of the modalities for cancer treatment. One example is microwave hyperthermia which is a thermal therapy for carcinoma based on the decrease of the survival ratio of cancer cells by heating. In particular, we have been studying the intracavitary heating using the implanted biliary stent and a thin coaxial microwave probe combined with endoscope which is an effective and low-invasive treatment for deep-seated carcinoma such as a bile duct carcinoma. This paper describes the heating characteristics around the biliary stent by conducting both the heating experiments using muscle-equivalent phantom and the numerical simulations using the finite-difference time-domain (FDTD) method.
    10/2011;
  • Ryotaro Suga, Kazuyuki Saito, Masaharu Takahashi, Koichi Ito
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    ABSTRACT: Recently, Magnetic Resonance Imaging (MRI) system which operates up to under 3 T is being used in clinical practice in Japan. In order to achieve the requirement of obtaining more high-quality images and short imaging time, devices utilize high magnetic field (>3 T) and high power electromagnetic (EM) wave pulses has been developed. The rise of the static magnetic field is proportional to the increase of the EM wave frequency which brings down issues of variation in capacitance used in the radio frequency (RF) coil for MRI system. In addition, increasing power causes problems of withstanding voltage and these approach leads to generation of non-uniform magnetic field inside the RF coil. Hence, if we can develop the birdcage coil for MRI system with no lumped circuit elements, it is extremely useful. In this paper, birdcage coil without the use of lumped circuit elements for 4 T MRI system was proposed and its magnetic field distribution was investigated. As a result, it was confirmed that the proposed birdcage coil has equivalent performances of the conventional birdcage coil which includes several capacitors.
    10/2011;
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    ABSTRACT: Wireless power transmission is being investigated as a means to operate tiny medical equipments such as capsular endoscope that exists for a long time in the body. In this paper, we examine the wireless power transmission to a capsular endoscope by microwave as a new approach, in order to show its usability for medical applications. We propose power receiving antennas inside the endoscope that operates at 433.92 MHz and 915 MHz, respectively. We calculate maximum received power in the intestines by using these antennas. The results show that adequate power can be well received at 433.92 MHz. Index Terms — Capsular endoscope, loop antenna, microwave, receiver, wireless power transmission.
    01/2011;
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    ABSTRACT: Recently, electromagnetic interference (EMI) of an implanted pacemaker with a mobile radio terminal has been investigated. However, there are few studies of specific absorption rate (SAR) around the pacemaker by the mobile radio terminal. In this paper, the relation of SAR between the mobile radio terminal and the pacemaker embedded into the torso model has been investigated. As a result of calculations, possibilities of increasing the SAR were observed in some cases.
    01/2011;
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    ABSTRACT: Small implantable devices have been investigated with great interest for wireless medical applications because of the promise of different clinical usages in order to promote patient's independence. In these implanted device systems, the antenna plays an important role as a part of transmitting and receiving power. Therefore, the research on the antennas for implantable devices (implantable antennas) is important. In this study, we propose an implantable helical folded dipole antenna for short- range wireless communications. The antenna is designed to operate at 2.45 GHz, one of the industrial-scientific-medical (ISM) bands. We have analyzed some performances of the proposed antenna. The results show that the proposed antenna can be a candidate as an implantable antenna.
    01/2011;
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    ABSTRACT: Recently, numerous people are suffering from sleep apnea syndrome which is the respiratory problem during sleep, and lack of sleep would cause traffic accidents or even other diseases such as lifestyle-related diseases. In fact, it is quite difficult to be aware of those who have. This paper tries to solve early awareness by proposing a patch array antenna, which is designed for non-contact sensor to detect respiratory movement. The authors propose a four- element antenna to have the beam directivity that is changeable to the desired direction. The design and its calculation results are described.
    01/2011;
  • Ho-Yu Lin, Masaharu Takahashi, Kazuyuki Saito, Koichi Ito
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    ABSTRACT: Radio-frequency identification (RFID) is a developed technology and useful for several fields; moreover, it has promising for reducing medical error and receiving the patients’ information without connecting cable lines in hospitals. In this paper, we present an implanted RFID antenna with 50-ohm system for medical/health-care applications. The antenna is designed for one of the UHF band (951–956 MHz) and implanted into a three-layer phantom which represents human upper arm. Some characteristics including the S11 and the radiation pattern are calculated by use of the FDTD method and measured with the three-layer phantom.
    01/2011;
  • Source
    Basari Basari, Kazuyuki Saito, Masaharu Takahashi, Koichi Ito
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    ABSTRACT: Simple selectable-beam antenna system for vehicle-mounted mobile satellite communication applications was presented. We have discussed it from design, laboratory test as well as outdoor test and verification in measurement campaign. System components discussed include array antenna includes its switching system to activate the array, and satellitetracking function as well. The measurement in anechoic chamber was thoroughly examined with satisfactory performances, well suited with the calculations. The basic measurement included S11, axial ratio, and radiation pattern characteristics. Overall antenna system performances in anechoic chamber test gave satisfactory results. Further, the antenna system was also confirmed by using signal from satellite for immobile-state outdoor measurement on the testing-rig. Without any obstacles present, the system was able to correctly select the beam for tracking the satellite with regard to the rotation of the antenna. Following the satisfactory performances in anechoic chamber measurement and fixed-state outdoor measurement, the antenna system was also examined in measurement campaign using the satellite signal to verify the validity of the developed system for possibility use in land mobile satellite applications. We built a connection with the satellite and tested the antenna system in particular its tracking capability. As a result, the system was correctly track the satellite while vehicle was moving by considering its position and bearing information that retrieved from GPS module. In addition, we also considered and tested the antenna system under environment constraints that affecting its received signal power, such as buildings, roadside-trees, utility poles, highway overpasses and inclined-road present. The results showed us the blockage and shadowing happened and significantly attenuated the received signal owing to its
    08/2010; , ISBN: 978-953-307-135-0
  • Satoru Kikuchi, Kazuyuki Saito, Masaharu Takahashi, Koichi Ito
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    ABSTRACT: This study computationally assessed the temperature elevations due to electromagnetic wave energy deposition during magnetic resonance imaging in non-pregnant and pregnant woman models. We used a thermal model with thermoregulatory response of the human body for our calculations. We also considered the effect of blood temperature variation on body core temperature. In a thermal equilibrium state, the temperature elevations in the intrinsic tissues of the woman and fetal tissues were 0.85 and 0.61 degrees C, respectively, at a whole-body averaged specific absorption rate of 2.0 W kg(-1), which is the restriction value of the International Electrotechnical Commission for the normal operating mode. As predicted, these values are below the temperature elevation of 1.5 degrees C that is expected to be teratogenic. However, these values exceeded the recommended temperature elevation limit of 0.5 degrees C by the International Commission on Non-Ionizing Radiation Protection. We also assessed the irradiation time required for a temperature elevation of 0.5 degrees C at the aforementioned specific absorption rate. As a result, the calculated irradiation time was 40 min.
    Physics in Medicine and Biology 04/2010; 55(8):2411-26. · 2.70 Impact Factor

Publication Stats

133 Citations
28.13 Total Impact Points

Institutions

  • 2006–2011
    • Chiba University
      • • Graduate School of Engineering
      • • Graduate School of Science and Technology
      Tiba, Chiba, Japan
  • 2010
    • National Institute of Information and Communications Technology
      Edo, Tōkyō, Japan