高橋 応明

Meander Line Antenna (MLA) is widely employed in compact electronic devices, such as cellular phones and WLAN terminals, owing to its electrically small size. To facilitate practical antenna design, essential equations encompassing self-resonant structure, input resistance, antenna efficiency, and Q factor have been systematically developed. However, the prior self-resonant equations included only inductive reactance (XC), neglecting the capacitive reactance (XD) equation. This manuscript addresses this gap by introducing new design equations, presenting a newly derived XD equation and an improved Q factor expression. The inadequacies of the existing Q factor equation, reliant on the radius of a sphere encompassing the antenna, are addressed by proposing a more fitting expression that incorporates antenna structural parameters using the ratio of reactance to resistance. The overview of existing design equations sets the stage for the introduction of these newly developed equations. To assess the accuracy of electromagnetic (EM) simulation results, a comparative analysis is conducted between simulated and theoretically calculated input resistance values. The derivation of new reactance equations involves the development of XC equations based on electromagnetic theory. The XD equation is established by deriving the stored charge equation from electrical near-field distributions obtained through EM simulations. By applying the relationship between charge and capacitance, a new XD equation is obtained. Subsequently, a new self-resonant equation is derived, and the validity of the newly derived equations is confirmed through EM simulation results, ensuring their accuracy. Two MLA prototypes, with lengths of 0.05 and 0.1 wavelengths at 405 MHz, are fabricated and experimentally validated. Smith chart measurements confirm the self-resonant condition and input resistance. By correlating with the VSWR characteristics, the obtained Q factor of approximately 100 aligns successfully with the results from the reactance equation. The antenna gain is verified at -7.7 dBi and -3.5 dBi for antennas with lengths of 0.05 and 0.1 wavelengths, respectively. These findings establish the practical applicability of the proposed equations for antenna design and elucidate the performance of practical antennas.

Abstract In the COVID-19 pandemic, lockdown and acryl partitions were adopted as countermeasures against droplets/aerosol infections; however, these countermeasures restrict communication. In this study, a blocking device was developed using negative ions and an electric field. The device blocks mists simulating droplets/aerosol by a maximum of 89% but transmits light and sound, which is important for communication. The device demonstrated effective blocking performance for aerosol, including the COVID-19 virus spread from patients in a clinic. Our device can help prevent infections without disrupting communication.

Obstacles on railway tracks are a factor hindering safe and stable operation. For this reason, obstacle detection systems have been introduced at level crossings, slopes and under platforms. However, they have been introduced only in limited sections for limited applications. Therefore, the authors considered to introduce an obstacle monitoring system that combines 90 GHz band millimeter-wave and Radio over Fiber (RoF) technology, as an obstacle monitoring system over tracks to monitor the entire line. Since the millimeter-wave band has a wide bandwidth, high precision detection is possible when they are used in radar. In addition, since radar control units can be grouped in one place by introducing the RoF technology, we can build a system at a low cost. In order to study the feasibility of introducing a new obstacles monitoring system combining 90 GHz band millimeter-wave and RoF technology in railway environment, a field test using prototype equipment was conducted on a railway track. As a result, it was confirmed that the prototype radar system could detect humans and non-metallic objects entering a track at a distance of about 200 m from the location of the prototype system. These results shows that the proposed system has the potential to be introduced as a new railway obstacle monitoring system using 90 GHz band millimeter-waves and RoF technology. © 2023 The Authors. IEEJ Transactions on Electrical and Electronic Engineering published by Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Various small focus spot applicators are being investigated for hyperthermia therapy, which requires microwave concentration to heat tumors in the human body. Dielectric lens antenna is frequency independent and has strong focusing capability to achieve a very small focusing spot. In this paper, lenses with diameters of 30, 50 and 70 cm were designed to evaluate the size of the focal spot in the human body model. The electromagnetic simulator, FEKO was used to generate rays and near-field focusing data of dielectric lenses at a frequency of 2.45 GHz. The simulated focal spot sizes agreed well with the theoretical values. An analytical investigation into the power at the focal spot was conducted using the proposed power relations of the focused lens novel equation. The theoretical propagation loss is used to represent the power density degradation at the focal spot caused by microwave absorption by the human body. The simulation results of the focused lens in the human body indicated that the 30 cm lens achieved a larger focal spot with a greater focusing power, 0.714 mW compared to the 70 cm lens, which achieved a smaller focal spot but a lower focusing power, which was 0.393 mW.

When divers are doing rescue operations in the sea, they are in a hazardous environment. If it becomes possible to know their positions accurately, rescue operations can be carried out more safely and reliably. We propose a subsea position estimation system using received signal strength (RSS) of electromagnetic waves to assist rescue operations by locating divers in the sea. In this report, as a basic study for introducing machine learning into the subsea position estimation system, four supervised machine learning models were used for undersea position estimation and each model is compared. The best model is Multi-Layer Perceptron (MLP), and it is confirmed that there is no problem in real-time computation time for all models.

When divers rescue people in accidents at sea, they are exposed to dangers such as injuries by obstacles, and so on. If the divers can confirm their position, their rescue activities will become safer. In the previous study, assuming that we specify the positions of the divers performing rescue operations to support their work, we developed a 3D undersea position estimation algorithm communicating between the undersea and the sea surface. However, we did not yet consider the effects and countermeasures of sea waves. In this paper, we indicate the effects of sea waves on the algorithm and investigate wave countermeasures.

When divers rescue people from accidents at sea, they are in danger because of obstacles floating in the sea. If divers can confirm their own position, their activities will become much safer. In this study, assuming that we specify the positions of the divers performing rescue operations, to support their work, we investigate an undersea positioning technology using electromagnetic waves with low frequencies, i.e., 10 kHz. In previous studies, an ultra-long wave of 10 kHz was theoretically attenuated at 3.5 dB/m. In addition, a simulation of position estimation in the vertical section of the sea was reported. In this study, we indicate the superiority of using receiving signal strength (RSS) to the phase difference between a transmitted and received signal. We also investigate an algorithm for position estimation wherein the antenna characteristics and two propagating rays of electromagnetic waves at sea are considered. Finally, we estimate the position of the transmitting antenna at depths of 1 to 8 m using our algorithm.

<p>With the growing aging society, extending healthy life expectancy has been attracting attention. Small devices using IoT and wireless technologies are expected to have effect on self-health management. However, batteries and power cables cause problems such as the restriction on human motion or the devices' size. Therefore, wireless power transmission (WPT) addresses these problems and use of WPT may help with improving daily health care management. In this paper, we propose a WPT system between mobile devices and a sensor on the fingertip by using Near Field Communication (NFC). The proposed system can transfer enough power for IoT sensors.</p>

本論文では，モバイル端末のタッチパネルディスプレイと統合された，5GのSub-6 GHzで動作する移動通信用アンテナの実現を目的として，タッチパネルディスプレイと統合されたMIMOアンテナのモデルを数値解析し，評価した．

近年，携帯無線端末は，安定して大容量データを伝送すべく，複数のアンテナを使用するダイバーシチ技術やMIMO (Multiple-Input Multiple-Output)技術が使用されている．一方，情報端末には小型化も求められる．そのため，各アンテナ単体の体積小形化だけではなく，端末内でのアンテナの近接配置によるアンテナシステム全体としての必要体積小形化も求められる．しかしこの場合，アンテナ間で強い電磁結合により，アンテナ効率が減少し，所望の通信距離や通信容量が得られないなどの問題が生じる．本論文ではMIMOを想定し，平面上に直線配置したモノポールアンテナ3素子に対し，3アンテナ間全ての結合を低減する手法を提案する．従来手法では必要であった両端のアンテナ間の接続を不要とすることで，アンテナを飛び越す立体構造を必要としない構成とした．今回の解析モデルでは，両端と中央のアンテナ間結合を12.3 dB，両端のアンテナ間結合を8.6 dB低減させ，これによりアンテナ効率が両端のアンテナで1.5 dB，中央のアンテナで7.5 dBの向上を確認した．

<p>In recent years, a capsule endoscopy has been used as a medical device to diagnose small intestines painlessly. Wireless power transmission (WPT) to the capsule endoscopy has been studied. The efficiency of WPT can be improved by using location information of the capsule. In the previous research, a localization method for the WPT was developed in simulation. In the present paper, we evaluated the localization algorithm developed in the previous research by measurement, so that the effectiveness of the algorithm was demonstrated.</p>

<p>Biological information monitoring systems are widely used to obtain and monitor the vital signs of patients in hospitals. However, the current system mainly uses the 420-450MHz band, making it difficult to manage channel switching, adding and removing equipment and so on, unless you are an expert in wireless communications. There is also the problem of having to carry a transmitter that is the same size as a small terminal. Therefore, we proposed a textile antenna using the 5.2 GHz band as a replacement for the system's transmitter antenna. In this paper, we report the antenna characteristics of the transmitter antenna designed by the authors when it is attached to the human body, the received power results of the transmitter power by analyzing the textile antenna in a simulated real-world environment model.</p>

<p>The millimeter-wave band is being focused as a frequency band in which high-speed and large-capacity communication can be realized, and various approaches for practical use have been made. In this paper, we studied the attenuation characteristics of the 45 GHz with the moisture contents and thickness of snow, which had never been studied and is expecting to be used in next-generation train communication systems and 5G. The characteristics are also compared with ones of 60 GHz which can be used for new Wi-Fi standard (IEEE 802.11ad). As the result, it is found that when snow accretes to the surface of the antenna radome, the attenuation increases as the moisture content increases and we can not neglect the influence on wireless communication using millimeter-waves.</p>

© 2002-2011 IEEE. The impedance expansion method (IEM) is a circuit modeling technique for electrically very small devices based on the method of moments. In the authors' previous work, a circuit model of a wireless power transfer system was developed using the modal IEM, which utilizes the IEM and eigenmode analysis, wherein the currents on the coils were expanded into thin-wire basis functions. However, surface basis functions are required to apply the modal IEM to arbitrarily shaped conductors. In this letter, the problems arising when the surface basis functions are applied to the modal IEM are pointed out, and the cause of these problems is clarified. Then, the resolvability of these problems is demonstrated using the loop-star basis functions.

© 1963-2012 IEEE. The impedance expansion method (IEM), which has been previously proposed by the authors of this paper, is a circuit modeling technique for electrically very small devices. This paper describes a circuit modeling procedure that utilizes the IEM and eigenmode analysis for a wireless power transfer system. First, a multimode circuit model that can represent the higher order resonances in a broadband frequency range is presented. Subsequently, a single-mode circuit model - consisting only of passive elements - that can represent both the radiated and conduction loss powers at approximately its operating frequency band is presented.

<p>In recent years, many small antennas used near a human body have been proposed in the medical field. Most of them are designed in consideration of the influence of a human body having high dielectric properties and assume use at a single frequency or a single polarization. We proposed a dual-polarized textile antenna for the 5.2 GHz band as our previous study.</p><p>In this paper, we report the design of a dual-band dual-polarized antenna using single point coplanar feeding. This antenna has excellent radiation patterns and reflection coefficients for each of the desired frequency.</p>

<p>In recent years, MIMO technology is used in many mobile terminals to increase channel capacity. MIMO uses multiple antennas, however, if MIMO antennas are put closely such as a small terminal, a strong mutual coupling occurred. Then it causes decreasing radiation efficiency and channel capacity.</p><p>Besides, CA technology which uses multiple frequencies is also utilized. Therefore, reducing the mutual coupling at multiple frequencies is required corresponding to CA. In the previous study, a method of adding a branch element connecting by inductor L and capacitor C has been proposed. In this paper, focusing on the relationship between the number of decoupling frequencies and current paths, we propose a novel triple-band decoupling method without connecting and confirm that the proposed model performed decoupling and increased radiation efficiency.</p>

<p>In recent years, MIMO technology which uses multiple antennas has been introduced to the mobile terminal to increase communication capacity per unit frequency. However, if MIMO antennas are put closely, a strong mutual coupling occurred. Moreover, CA which uses multiple frequencies is also utilized to improve communication speed. Therefore, reducing mutual coupling in multiple frequencies is required. In this paper, we propose a dual-band decoupling method by using a short stub and a branch element and confirmed that the proposed model performed decoupling, increased radiation efficiency.</p>

<p>MIMO technology, which uses multiple antennas, has been introduced to the mobile terminal to increase communication capacity per unit frequency. However, MIMO suffers from the problem of mutual coupling. If MIMO antennas are closely packed, as in a small wireless terminal, a strong mutual coupling occurs. The mutual coupling degrades radiation efficiency and channel capacity. As modern terminals are likely to use three MIMO antennas, reducing the mutual coupling 3×3 MIMO is essential. Some decoupling methods for three elements have been proposed. Unfortunately, these methods demand that the elements be cross-wired, which complicates fabrication and raises the cost. In this paper, we propose a non-connected decoupling method that uses short stubs and an insertion inductor and confirms that the proposed model offers excellent decoupling and increased radiation efficiency.</p>

<p>In recent years, capsule endoscopy has attracted attention as one of the medical devices that examine internal digestive tracts without burdening patients. Wireless power transmission of the capsule endoscope has been researched now, and the power transmission efficiency can be improved by knowing the capsule location. In this paper, we develop a localization method wireless power transmission. Therefore, a simple algorithm for using received signal strength (RSS) has been developed so that position estimation can be performed in real time, and the performance is evaluated by performing three-dimensional localization with eight receiving antennas.</p>

生体情報モニタリングシステムは患者の状態を逐次把握し，容態の急変等に対応するために不可欠なシステムであるが，送信機と患者間のケーブルによる身体の動作制限や，送信機の装着により生じる不快感などの問題がある．そこで，送信用布アンテナとして5.2 GHz帯布アンテナを用いることで装着時の患者のストレス軽減と安定した通信を見込むことができる．本論文では，水平・垂直の両偏波に対応する5.2 GHz帯生体情報モニタリング用布アンテナを提案するとともに，本アンテナが人体近傍に設置された場合や使用中に湾曲した場合でも良好に動作することを確認した．また，実際に本アンテナを使用して無線LAN周波数を利用した受信信号強度の測定を行うことで，本アンテナを用いた無線通信が可能であることを示した．

<p>Nowadays, mobile communication technology has become essential; thus, it is important to consider the effect of electromagnetic radiation from mobile terminals such as smartphones on the human body. In this study, we calculated the specific absorption rate (SAR) and temperature increase in pregnant women exposed to a smartphone's radiation at 13, 18, and 26 weeks of gestation. The results indicate that the SARs were much lower in fetuses than in pregnant women under all of the calculation settings in this study. Moreover, the maximum temperature increases in fetuses were half of those in pregnant women.</p>

<p>Recently, the capsular endoscope that has extra function has been investigated. Although the power consumption tends to increase as the ability increases, it is difficult to increase the capacity of the battery due to the volumetric problem. In this study, we proposed an antenna for both wireless power transmission and image transmission to be mounted on a capsule endoscope. In this paper, we discussed the requirements desired to antennas to be mounted in capsular endoscope.</p>

<p>In recent years, MIMO technology which uses multiple antennas has been introduced in mobile terminal to increase communication capacity. However, if MIMO antennas are put closely, a strong mutual coupling occurred. Then it causes decreasing radiation efficiency and channel capacity. Therefore, reducing the mutual coupling is required. In previous study, connecting MIMO antennas by inductor L or added branch elements to antennas instead of L. In this paper, we propose a novel decoupling method by using a short stub and confirm that proposed model performed decoupling, increased radiation efficiency.</p>

<p>The impedance expansion method (IEM), which has been previously proposed by the authors, is a circuit-modeling technique for electrically-very-small devices. This paper provides a new idea on the principle of undesired radiation in wireless power transfer systems by employing IEM. In particular, it is shown that the undesired radiation is due to equivalent infinitesimal dipoles and loops of the currents on the coils.</p>

<p>The impedance expansion method (IEM), which was previously proposed by the authors, is a circuit-modeling technique for electrically-very-small devices. The equivalent circuits derived by the IEM include dependent voltage sources proportional to the powers of the frequency. However, the previous report did not describe how circuit simulators could realize such dependent voltage sources. This paper shows how this can be achieved by approximating the equivalent circuit using only passive elements.</p>

<p>This paper proposes a circuit modeling technique for electrically-very-small devices, e.g. electrodes for intrabody communications, coils for wireless power transfer systems, high-frequency transformers, etc. The proposed technique is based on the method of moments and can be regarded as an improved version of the partial element equivalent circuit method.</p>

本論文では，RFIDを用いた乳児姿勢検知システムを提案する．近年，それまで元気だった乳児が突然死亡する，乳幼児突然死症候群（SIDS : Sudden Infant Death Syndrome）が注目されている．明確な原因は不明であるが，うつぶせの状態寝での発症リスクが高いとされている．そこで本論文ではRFIDを用いて，乳児のうつぶせを検知するシステムを提案した．乳児が着用する服に取り付けるタグアンテナを導電布で設計し，数値シミュレーションと通信実験により評価し，提案するシステムの実現性を示した．

Along with the spread of novel types of mobile phones such as smartphones, there has been increasing public interest in the health hazards associated with exposure to electromagnetic waves from these devices. Therefore, we estimated the specific absorption rate (SAR) of electromagnetic radiation by numerical simulation using a realistic computational smartphone model with an antenna for a third generation communication (3G) system (operating frequencies: 900 MHz and 2 GHz) and computational human models with the anatomical structures of Japanese male and female adults. We also assessed the relative variability of SAR based on holding a smartphone at various positions for data communications. The 10-g-averaged SAR (SAR10g) when the smartphone was operating at 2 GHz was generally higher than that at 900 MHz independent of the placement of the smartphone. Moreover, we found that SAR10g had a tendency to increase when the smartphone was placed vertically in relation to the torso. In addition, it is possible that SAR10g variability depends mainly not on placement height but on tilt angle.

<p>Technology of MIMO using multiple antennas and Carrier Aggregation operating multiple frequency bands are introduced in a mobile terminal to improve communication capacity. However, if plural MIMO antennas are installed closely, mutual coupling between the antennas must be reduced to suppress deterioration of radiation efficiency and increase of correlation coefficient. In this paper, we proposed a decoupling method for dual-band using trifurcation elements. Moreover, it is confirmed to be broadened decoupling bandwidth by optimizing branch width and length.</p>

Electromagnetic interference (EMI) from mobile phones affecting implanted cardiac pacemakers has become a recent concern. In previous numerical computations of the EMI, a half-wavelength dipole antenna has been employed as a radiator of electromagnetic waves. However, current mobile phones are generally equipped with an internal antenna. Furthermore, recent mobile phone systems are operated at higher frequencies, i.e., 2 GHz, whereas lower frequencies around 900 MHz have been assumed in the previous studies. In this study, a mobile phone with an internal antenna was modeled with a planar inverted-F antenna (PIFA) mounted on a metallic case, in order to calculate the interference voltage induced at the pacemaker due to the internal antenna. The PIFA was then scanned in a plane parallel to the torso surface, in order to calculate the interference voltage at each position and to clarify the detailed relationship between the interference voltage and the position of the antenna. Moreover, the interference voltage was experimentally evaluated to validate the numerical calculations. It is shown that the PIFA has interference voltage characteristics, which differ from those of the half-wavelength dipole antenna. Comparing the calculation with the measurement, both results show the same tendency, especially around the position of maximum interference. Therefore, the measured results indicate the validity of the numerical results.

Recently, wearable wireless devices or terminals have become hot a topic not only in research but also in business. Implantable wireless devices can temporarily be utilized to monitor a patient's condition in an emergency situation or to identify people in highly secured places. Unlike conventional wireless devices, wearable or implantable devices are used on or in the human body. In this sense, body-centric wireless communications (BCWCs) have become a very active area of research. Radio-frequency or microwave medical devices used for cancer treatment systems and surgical operation have completely different functions, but they are used on or in the human body. In terms of research techniques, such medical devices have a lot of similarities to BCWCs. The antennas to be used in the vicinity of the human body should be safe, small and robust. Also, their interaction with the human body should be well considered. This review paper describes some of the wearable antennas as well as implantable antennas that have been studied in our laboratory.

Until now, the 700 MHz band has been used for the field pickup unit (FPU), which is used for the live broadcasting of events, such as marathons and long-distance relay races. However, the frequency band is slated to migrate to 1.2 and 2.3 GHz bands based on an action plan for radio spectrum reallocation developed by the Ministry of Internal Affairs and Communications, Japan. With the frequency migration of the FPU, the size of transmitting antennas can be downsized. Therefore, 1.2 and 2.3 GHz band antennas can also be mounted on wireless cameras for professional-use. In this study, we measured the specific absorption rate (SAR) on the body of the operator exposed to electromagnetic waves radiated from the transmission antenna of the wireless camera via a 1.2 GHz band. We also calculated the SAR to confirm the validity of the measurement method, and we compared the measured results with the calculated ones. As the result, SAR distributions between the measured and the calculated results were nearly identical. It is thus possible to evaluate the SAR using the method suggested in this paper.

With the development and diverse use of wireless radio terminals, it is necessary to estimate the specific absorption rate (SAR) of the human body from such devices under various exposure situations. In particular, tablet computers may be used for a long time while placed near the abdomen. There has been insufficient evaluation of the SAR for the human body from tablet computers. Therefore, we investigated the SAR of various configurations of a commercial tablet computer using a numerical model with the anatomical structures of Japanese males and females, respectively. We find that the 10-g-averaged SAR of the tablet computer is strongly altered by the tablet's orientation, i.e., from -7.3dB to -22.6dB. When the tablet computer is moved parallel to the height direction, the relative standard deviations of the 10-g averaged SAR for the male and female models are within 40%. In addition, those for the different tilts of the computer are within 20%. The fluctuations of the 10-g-averaged SAR for the seated human models are within ±1.5dB in all cases.

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.

MIMO technology has been widely used for several years for the purpose of improving communication speed and communication capacity. However, if MIMO antenna is mounted closely, radiation efficiency and throughput of MIMO are decreased due to strong mutual coupling. In this paper, a decoupling method using meander branch antenna is proposed. It is confirmed that the mutual coupling is reduced and the radiation efficiency is increased by utilizing this method. Moreover, further developing this method, it is confirmed that a decoupling bandwidth can be enhanced.

This chapter describes the implanted antennas to be applied to medical situations. One is the PIFA loaded onto a cardiac pacemaker for use in the 400MHz Medical Implant Communications Service (MICS) band another one is the helical dipole antenna for the industrial scientific medical (ISM) band. It evaluates the implanted antenna models were numerically analyzed by the finite-difference time-domain (FDTD) method and the antenna characteristics. The chapter analyzes the antenna characteristics of an antenna implanted in a multilayer medium model. Moreover, implanted antennas were buried into high-resolution numerical human models and the effectiveness of these antennas and the validity of the multilayered structure model were investigated by numerical analysis. As a result, it is possible to use these implantable antennas for health care wireless communication systems.