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ABSTRACT: Wireless power transmission is being investigated as a means to operate tiny medical devices such as the capsular endoscope, which is able to exist for a long period during diagnostic procedures within the body. In this paper, we examine the wireless power transmission to a capsular endoscope by microwaves to show its usability for medical applications. A modified helical antenna inside the endoscope is proposed as a power receiving antenna, operating at 430 MHz band. By calculating a maximum received power in the stomach using such antenna, the results show that adequate power can be well received.
General Assembly and Scientific Symposium, 2011 XXXth URSI; 09/2011
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ABSTRACT: In recent years, various types of medical applications of microwaves have widely been investigated and reported. Among them, microwave thermal therapy is one of the useful applications and is modality for cancer treatment. In this treatment, there are several schemes of microwave heating. The authors have been studying thin coaxial antenna for intracavitary microwave heating aiming at the treatment of bile duct carcinoma. In this treatment, an endoscope is first inserted into the duodenum and a long and flexible coaxial antenna is then inserted into the forceps channel of the endoscope, which is used to insert the tool for surgical treatment. Finally, the antenna is guided to the bile duct through the papilla of Vater, which is located in the duodenum, and is inserted in the bile duct. Up to now, the heating characteristics of the antenna are investigated by numerical simulation, experiment using tissue-equivalent phantom and extracted organs. In this study, the authors have an experience on animal experiment using a swine. In the experiment, temperature rises around the antenna inserted into the bile duct were measured. From the results of this experiment, cooling effect by blood circulation was cleared.
General Assembly and Scientific Symposium, 2011 XXXth URSI; 09/2011
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ABSTRACT: This paper presents a field measurement of a simple antenna system mounted on a vehicle by utilizing a geostationary test satellite called Engineering Test Satellite VIII (ETS-VIII). Our developed antenna system is compact, lightweight, and promising for low-cost production. The antenna system is constructed by a 16-cm patch array antenna, which has simple satellite tracking that is controlled by a control unit as the vehicle's bearing is updated from a navigation system in real time. A Global Positioning System (GPS) module is utilized for the navigation system to provide accurate information of the vehicle's position and bearing during traveling. A control unit is provided as antenna-beam control and measured-data acquisition. We thoroughly examine the developed system in field measurements under open field areas and blockage areas in order to evaluate the propagation characteristics caused by utility poles, pedestrian overpasses, and vegetation-covered roads. In this measurement, the received signal power and the average bit error rate (BER) are simultaneously retrieved. Steadily received levels and average BER are satisfactorily attained during satellite tracking in open field areas. Moreover, the fade characteristics and average BER performance are also investigated during signal blockage. The results show that different environments give different degrees of attenuation, which affects the BER performance in terms of fade depth. Ultimately, our proposed antenna system can contribute to the design of future cost-effective mobile satellite communications.
IEEE Transactions on Vehicular Technology 12/2010; · 1.92 Impact Factor
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ABSTRACT: Microwave thermal therapy is one of the modalities for cancer treatment. There are several schemes of microwave heating. The authors have been studying thin coaxial antenna for intracavitary microwave heating aiming at the treatment of bile duct carcinoma. Up to now, the heating characteristics of the antenna are investigated by numerical simulation and experiment for finding a possibility of the treatment. In this study, in order to consider practical situations of the treatment, heating characteristics of the antenna inserted into a metallic stent is evaluated by numerical simulations. Moreover, the relation between coagulation size of the tissue and the radiation power from the antenna is investigated experimentally. It must be considered, when the input power of the antenna is high (around several tens of watts). From these investigations, some useful results for practical treatments were found.
Engineering in Medicine and Biology Society (EMBC), 2010 Annual International Conference of the IEEE; 10/2010
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ABSTRACT: In recent years, a study on body-centric wireless communications has become an active and attractive area of research because of their various applications such as e-healthcare, support systems for specialized occupations, personal communications, and so on. Whereas UHF bands are subjects of interest especially in Europe and USA, relatively low frequency bands below several megahertz are of great interest especially in Japan. Hence, all of the prospective frequencies are in an extremely wide range, and an objective idea on how to select a right frequency band for individual applications is required. Currently in our laboratory, we have been studying on frequency dependence of basic characteristics of wearable antennas as well as body-centric wireless communication channels in the range of HF to UHF (3 MHz-3 GHz). There are experimental, analytical, and numerical ways to clarify the basic characteristics of the antennas and communication channels. In experiments, we have to ensure impedance matching at certain frequency points because of sensitivity limitations; therefore, it is hard to obtain such broadband characteristics. Theoretical analysis is useful to understand physical mechanism; however, complex geometry and motion of the human body cannot be modeled. By contrast to them, numerical simulation can solve complex problems with relative ease. For example, Hall et al. have shown that the dynamics of the human body can be modeled by dividing the motion into several frames, and the simulated results agree with the measured results. Also in our study, observations of channel characteristics are conducted by employing numerical simulations. In this paper, firstly, electric field distributions around the human body wearing a small top-loaded monopole antenna are numerically calculated and compared in a wide range of HF to UHF bands. Then, received open voltages at receiving antennas which are equipped at several different points on the human body are numerically inve-
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stigated. The received open voltages are also numerically calculated and compared with several different postures of the human body. Statistic characterization and experimental validation will be necessary in further studies.
Applications of Electromagnetism and Student Innovation Competition Awards (AEM2C), 2010 International Conference on; 09/2010
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ABSTRACT: Implantable devices have been investigated with a great interest as communication tools. These implantable devices are embedded into the human or animal body. The vital information (e.g., glucose, blood pressure, and temperature) can be transmitted from implantable devices to the external equipments through wireless communication link. This paper shows a one of the application for a human in a sickroom. By using an implanted device, patient's events can be detected immediately. Then the implanted device sends the alert wirelessly to the home appliance which is connected to a hospital information system via a secured network link. A physician receives the alert and can decide to check back with the patient. In general, the implantable devices is have a bidirectional radio that can communicate with a paired radio carried within an external appliance. The external appliance could be a home monitoring device or a portable equipment, such as a cell phone, that provides the patient with increased mobility and a short-range wireless communication [4]. Therefore, the antenna for implanted devices is a key components in these telemetry systems. There are several issues to be considered in the design of an in-body antenna, including power consumption, size, frequency, biocompatibility, etc. This paper proposes an implanted helical folded dipole antenna for a short-range wireless communication at 2.45 GHz. Moreover, the implantable device is supposed to be embedded into human body using a syringe. According to this demand, the proposed antenna has a circular cylindrical shape of 1-mm diameter and 17.7-mm length. The antenna performances were investigated by use of the finite-difference timedomain (FDTD) calculation.
Antennas and Propagation Society International Symposium (APSURSI), 2010 IEEE; 08/2010
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ABSTRACT: In recent years, body-centric wireless communications have become an active area of research due to their various applications. Whereas UHF bands are subjects of interest especially in Europe, relatively low frequency bands below several megahertz are also in researchers' and corporations' interest especially in Japan. Thus, all of the candidate frequencies are in an extremely wide range. Our purpose is to bring objective and unified idea on the frequency characteristics of body-centric wireless communication channels with small wearable antennas. In this paper, we numerically observe the open voltage at several receiving antennas, and examined three different postures.
Microwave Conference, 2009. APMC 2009. Asia Pacific; 01/2010
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ABSTRACT: Implantable devices have been investigated with great interest as communication tools. These implantable devices are embedded into the human or pet body. The vital information (such as temperature, blood pressure, cardiac beat, etc.) can be transmitted from implantable devices to the external equipment by use of a wireless communication link. Therefore, the research on the antenna for implantable devices (implanted antennas) is very important. This paper proposes an implanted H-shaped cavity slot antenna for short-range wireless communications. This type of antenna, which is designed to operate at the industrial-scientific-medical band (2.45 GHz), is investigated by using finite-difference time-domain calculation. We analyzed the performances of the proposed antenna which is embedded into the human body between the shoulder and the elbow. However, since the proposed antenna is too small to fabricate, a scale model is adopted for antenna measurements. Some characteristics of the scale model of the antenna are also calculated and measured by using the 2/3 muscle-equivalent phantom. The results show that the proposed antenna has promise for use in an implant.
IEEE Transactions on Antennas and Propagation 05/2009; · 2.15 Impact Factor
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ABSTRACT: Antennas and the propagation characteristics for body-area networks have become an active area of research. In this paper, a cavity slot antenna is proposed for onbody communications at 2.45 GHz. First, the antenna characteristics (input impedance, radiation pattern, and efficiency) are calculated by the finite-difference time-domain method. The results show that the proposed antenna has a relatively high efficiency of more than 50% even in the vicinity of the human body. Next, the onbody radio wave-propagation characteristics are investigated through numerical simulation and experimental measurements of the electric-field distributions around a phantom with a simplified shape of a human arm. Both sets of results are then compared and discussed. Finally, good agreement between the measured and the calculated results is confirmed.
IEEE Transactions on Antennas and Propagation 05/2009; · 2.15 Impact Factor
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ABSTRACT: The topic of body centric communications can be divided into three domains: (1) Communications from the body surface to a nearby base station; (2) both antennas are on the body surface; and (3) at least one antenna may be in a medical implant within the body. These three domains have been called off-body, on-body and in-body, respectively. The classification serves to highlight some of the technical challenges. They may also be encountered by the reader in some of the papers in this Special Issue. However the papers in the Issue have not been arranged in this way but rather in terms of the main topic, namely antennas and propagation.
IEEE Transactions on Antennas and Propagation 05/2009; · 2.15 Impact Factor
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ABSTRACT: Small implanted devices have been investigated with great interest for wireless medical applications due to the promise of different clinical usages in order to promote patient's independence. In these implanted device systems, an antenna plays an important role as a part of transmitting and receiving power. There are several issues to consider while designing an in-body antenna, including power consumption, size, frequency, biocompatibility, etc. In this study, we propose an implanted cavity slot antenna for short-range wireless communications. The antenna is designed to operate at 2.45 GHz, one of the ISM (Industrial, Scientific, and Medical) bands, and is investigated by using the FDTD (finite difference time domain) calculation. The size of the proposed antenna is about 1 mm times 1 mm times 9 mm so that it will be easily embedded into the human body. We have analyzed some performances of the proposed antenna and the results show that the proposed antenna can be a candidate as an implanted antenna.
Antennas and Propagation, 2009. EuCAP 2009. 3rd European Conference on; 04/2009
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ABSTRACT: In recent years, body-centric wireless communications become an active area of research due to their various applications such as e-healthcare, support systems for specialized occupations, and personal communications. Since the candidate frequencies for body-centric wireless communications widely range from MHz to GHz, dielectric properties of the human body tissues, relative dimensions of the human body to wavelength, and the propagation channels around the body extremely vary with frequencies. In this paper, to bring objective and unified idea on the frequency characteristics of body-centric wireless communication channels, electric field distributions around the human body wearing a small antenna in a wide frequency range of 2.5 MHz to 2.5 GHz are numerically calculated. The results show that behavior of the electric field distributions around the human body could be broadly divided into two ranges; below 100 MHz and above 250 MHz.
Antenna Technology, 2009. iWAT 2009. IEEE International Workshop on; 04/2009
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ABSTRACT: In this paper, the cavity slot antenna with the H-shape slot was proposed for the implanted antenna. Numerical results show that the proposed antenna resonates well at 2.45 GHz. In order to simplify the measurement, the antenna is fabricated using the scale model which is 2.5 times larger than original dimension of the antenna. The antenna characteristics are measured in the developed 2/3 muscle-equivalent phantom. The results show that the fabricated antenna works at 980 MHz band as expected. The antenna characteristics for the calculation and the measurement corresponded. From these results, it is confirmed that the proposed antenna can be used as the implanted antenna.
Antennas and Propagation Society International Symposium, 2008. AP-S 2008. IEEE; 08/2008
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ABSTRACT: Antenna system for land vehicle communications aimed at ETS-VIII applications was proposed. The proposed antenna system consists of an array antenna loaded with switching circuit onto which controlled by a developed program after receiving data input from gyro sensor of GPS unit. As a result, for an elevation angle El=48deg, three beams are electronically created in the azimuth direction with a minimum gain more than 5 dBic and an axial ratio less than 3 dB. In addition, the antenna beam could be automatically switched with good results.
Antennas and Propagation Society International Symposium, 2008. AP-S 2008. IEEE; 08/2008
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ABSTRACT: This paper introduces a new slot antenna based on structure of the metallized dielectric waveguide. The antenna is constructed by combining a radiating plate with a slot on the metallized dielectric waveguide. This radiating plate works as a quarter wavelength impedance transformer and so the antenna operates in wide frequency range. The simulation shows the frequency range of the single slot antenna is from 23 to 29 GHz that is desirable for the automotive UWB radar applications. Furthermore, the fact that changing the thickness of the radiating plate partially can control the antenna directivity flexibly is presented. Because the antenna is based on rectangular waveguide structure, it can be easily integrated with a high-Q filter. The prototype of the integrated antenna and filter with area of 50times30 mm<sup>2</sup> exhibits half-power beamwidth of 54.7deg in the horizontal and 16.2deg in the vertical, respectively, as well as the sharp bandpass characteristics of 25 to 28 GHz.
Microwave Symposium Digest, 2008 IEEE MTT-S International; 07/2008
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ABSTRACT: In this paper, a cavity-backed slot antenna for on-body BAN devices has been investigated. The electric field distributions inside and around the human body are numerically analyzed by the use of the FDTD method. According to the results, in the region on and near the human body, the dominant component of electric field is vertical to the body surface, and the propagation mode is assumed to be creeping wave. On the other hand, in the region inside the human body, dominant component of electric field is horizontal to the body surface, and the propagating direction is almost vertical to the body surface. Furthermore, in order to confirm the validity of the simulated results, measurement of the electric fields around the biological-tissue equivalent phantom was performed. The results showed that the measured and simulated electric fields are agreed well, and indicated validity of the simulation. As a farther study, antenna design will be investigated in view of properties of the BAN system.
Antenna Technology: Small Antennas and Novel Metamaterials, 2008. iWAT 2008. International Workshop on; 04/2008
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ABSTRACT: In this paper, we propose a configuration of antenna system for mobile ground terminal using GPS and gyroscope terminal unit as automatic-navigation system to track the ETS-VIII satellite. To miniaturize the antenna system we introduce an electronically tracking rather than mechanically by use of a developed control program. With this configuration the antenna system becomes light and low profile with more in reliability and high-speed beam scanning possibility. In this research, a left hand circularly polarized array antenna integrated with an onboard switching circuit is proposed. Measured results of return loss, axial ratio, elevation cut pattern and beam switching performance are presented.
Antenna Technology: Small Antennas and Novel Metamaterials, 2008. iWAT 2008. International Workshop on; 04/2008
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ABSTRACT: This paper proposed a PIFA with an artificial cardiac pacemaker for use of MICS. The calculation model is composed of the PIFA and the pacemaker embedded in the 2/3 muscle-equivalent phantom. The distance between the surface of the phantom and the antenna is changed and the model is numerically analyzed by use of the FDTD method. Numerical results show that as the distance d increases, the real part of the input impedance and the resonant frequency shift to the lower due to the high permittivity and conductivity of the human tissue. However, the proposed antenna resonates well at 402-405 MHz band when the distance d is 6, 9, 12 mm. According to the radiation characteristics, the maximum gain is about -28 dBi. Moreover, the antenna is fabricated and the input characteristic is measured in the developed 2/3 muscle equivalent phantom. The results show that the fabricated antenna works well at 400 MHz band. From these results, it is expected that the proposed antenna can be used as the implanted antenna for MICS.
Antenna Technology: Small Antennas and Novel Metamaterials, 2008. iWAT 2008. International Workshop on; 04/2008
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ABSTRACT: An antenna which is combined the lineally polarized hexagonal shaped feed patch and the square shaped parasitic patch is proposed for wideband circular polarization antenna. The mechanism of wideband characteristics is clarified.
Antennas and Propagation Society International Symposium, 2007 IEEE; 07/2007
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ABSTRACT: This paper presents novel structure of the dielectric waveguide filter suitable for reflow soldering at millimeter wave frequencies. The filter is made of crystalline quartz, and given new 110 terminal structure. The measured unloaded quality factor of the dielectric waveguide resonator made of crystalline quartz is 1470 at 60-GHz band. The fabricated 4-pole bandpass filter consisting of the resonator and the new 110 terminal structure shows good performance. The measured maximum insertion loss in the passband of the filter with bandwidth of 1GHz is 1.5 dB.
Microwave Symposium Digest, 2005 IEEE MTT-S International; 07/2005
