Masaharu Takahashi

Chiba University, Tiba, Chiba, Japan

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Publications (77)48.26 Total impact

  • Hiromasa Nakajima, Masaharu Takahashi
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    ABSTRACT: In previous study, a monitoring system of removing intravenous drip (IV) needles by RFID is suggested and evaluated. When patients removed their IV needles, this system alerts the accidents to nurses. This paper tries to improve this system by use of improved antennas in order to reduce false-positive. For our proposed system, a tag antenna and a reader antenna are designed. In addition, characteristics of these antennas are calculated. Moreover, our proposed system is evaluated by use of a fabricated antennas and an examinee. From the results, this paper shows a stable monitoring system of removing IV needle.
    01/2015; 4(2):38-43. DOI:10.1587/comex.4.38
  • Ho-Yu Lin, Masaharu Takahashi, Kazuyuki Saito, Koichi Ito
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    ABSTRACT: In the above paper (ibid., vol. 61, no. 3, pp. 1363-1370, Mar. 2013), the units of the required RX power RP and available RX power AP erroneously appeared as [dB], whereas they should have appeared as [dB/Hz].
    IEEE Transactions on Antennas and Propagation 03/2014; 62(3):1543-1543. DOI:10.1109/TAP.2014.2298869 · 2.46 Impact Factor
  • Hoyu Lin, Masaharu Takahashi, Kazuyuki Saito, Koichi Ito
    IEICE Transactions on Communications 01/2014; E97.B(1):129-136. DOI:10.1587/transcom.E97.B.129 · 0.33 Impact Factor
  • 01/2014; 3(2):55-60. DOI:10.1587/comex.3.55
  • 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. DOI:10.1109/TAP.2013.2272672 · 1.15 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. DOI:10.1109/TAP.2013.2246534 · 2.46 Impact Factor
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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, transmitting antennas and the transmitting system that operates at 433.92 MHz. 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.
    Journal of Medical Imaging and Health Informatics 03/2013; 3(1):107-111. DOI:10.1166/jmihi.2013.1141 · 0.62 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. DOI:10.1109/TAP.2012.2227099 · 2.46 Impact Factor
  • 01/2013; 2(12):507-511. DOI:10.1587/comex.2.507
  • Kazuyuki Saito, Masaharu Takahashi, Koichi Ito
    IEICE Transactions on Electronics 01/2013; E96.C(9):1178-1183. DOI:10.1587/transele.E96.C.1178 · 0.39 Impact Factor
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    ABSTRACT: In-body wireless communication has attracted increasing attention because it can not only be used in medical application but also be combined with wireless communication to replace the existing connectivity in biological telemetry monitoring [1]. Therefore, it is possible to integrate radio frequency identification (RFID) system into a brand-new device [2]. However, it has been very difficult to combine them due to high lossy of human body. In this paper, an implantable tag antenna which is designed to match an integrated circuit (IC) chip of 9.3-j55.2Ω [3] is proposed and realized in experiment. The dimensions of proposed antenna is 15.75mm × 4mm. The impedance characteristic of proposed antenna is analyzed by finite-difference time-domain (FDTD) method. By introducing the three-layered phantom, the measurements of impedance characteristic is implemented; moreover, the maximum read range of 1.3cm is confirmed by a handy reader.
    01/2013; 2(8):347-351. DOI:10.1587/comex.2.347
  • IEICE Transactions on Communications 01/2013; E96.B(9):2244-2250. DOI:10.1587/transcom.E96.B.2244 · 0.33 Impact Factor
  • 01/2013; 2(3):98-103. DOI:10.1587/comex.2.98
  • 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
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    ABSTRACT: The research on body-centric wireless communications (BCWCs) is becoming very hot because of numerous applications, especially the application of E-health systems. Therefore, a small multi-band and low-profile planar inverted-F antenna (FIFA) with tuning function is presented for BCWCs in this paper. In order to achieve multi-band operation, there are two branches in the antenna: the longer branch low frequency band (950-956 MHz), and the shorter branch with a varactor diode embedded for high frequency bands. By supplying different DC voltages, the capacitance of the varactor diode varies, so the resonant frequency can be tuned without changing the dimension of the antenna. While the bias is set at 6 V and 14 V. WiMAX and ISM bands can be covered, respectively. From the radiation patterns, at 950 MHz, the proposed antenna is suitable for on-body communications, and in WiMAX and ISM bands, they are suitable for both on-body and off-body communications.
    IEICE Transactions on Communications 10/2012; E95.B(10):3074-3080. DOI:10.1587/transcom.E95.B.3074 · 0.33 Impact Factor
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    ABSTRACT: Radio frequency identification (RFID) system has been expected to be expanded in new fields. This paper shows a sensing system for urination by embedding an RFID tag into a paper diaper. The urination could be checked by change of the antenna characteristics. It could be possible to reduce physical and mental strain of both patients and their care personnel. In order to detect the urination, the RFID antenna was designed and the characteristics of the antenna were calculated. In addition, the antenna characteristics were measured with a phantom. As the result, urination considerably changes the antenna characteristics and that the system can be used to detect the urination.
    Advances in Science and Technology 09/2012; 85:59-64. DOI:10.4028/
  • 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. DOI:10.1109/TAP.2012.2207038 · 2.46 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 07/2012; 100(7):2356-2363. DOI:10.1109/JPROC.2012.2190129 · 5.47 Impact Factor
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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 06/2012; E95.B(6):2129-2132. DOI:10.1587/transcom.E95.B.2129 · 0.33 Impact Factor
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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 02/2012; 60(2):473-481. DOI:10.1109/TAP.2011.2173432 · 2.46 Impact Factor