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Implant sensors and robots are expected to sense biological information or images. They stay in the human body for a long time to make a diagnosis or move freely inside the body to perform remote treatment, such as excision of the affected area or drug injection. In this study, toward the aforementioned purpose, we developed a communication module with small antennas that use the 10-60-MHz band to enable high-speed implant communication to the deep part of the human body. A waveform equalization technique was also used to increase the transmission bandwidth limited by the small antennas and reduce the sizes of their implementation. As a result, an implant communication distance of 33 cm or more that can cover the entire human torso was achieved at a data rate of 20 Mb/s. Experimental results on a living swine also showed that the developed module is able to communicate deeper in the human body than all others reported in the literature at sufficiently high data rates. This article describes the development of the implant communication module and shows the current status of research by comparing its performance with others reported in the literature. [ABSTRACT FROM AUTHOR]

Impulse radio (IR) is a form of signal with ultrawide bandwidth spread spectrum suitable for short-range communications. In this paper, a triband on-body coil antenna for IR-based wireless capsule endoscope (WCE) communication system signal reception is proposed and experimentally verified. The proposed antenna contains three frequency bands (operating frequency: 38.5, 48.2, and 57.6 MHz) in 10–60 MHz band. For antenna transmission performance evaluation, three corresponding single-band in-body transmitting antennas are designed. Reflection and transmission coefficient, electric and magnetic field distributions, and specific absorption rate are simulated with a muscle equivalent phantom. In addition, transmission performance is measured in a liquid phantom by a battery powered IR transceiver. Measured results show that 50 mm attenuation is 32, 43, and 52 dB at 38.5, 48.2, and 57.6 MHz, respectively. It can be expected to realize a total data rate of 3.75 and 2.5 Mbps less than 50 and 90 mm, indicating that the proposed antenna can be used for WCE image reception. [ABSTRACT FROM AUTHOR]

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 SAR 10g 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. [ABSTRACT FROM PUBLISHER]

Microwave coagulation therapy (MCT) is an effective treatment for hepatocellular carcinoma. During MCT, the target region is heated to induce coagulation in the tissue, including cancer cells. Several types of antennas for MCT have been developed, the heating performances of which were evaluated via specific absorption rate (SAR) and temperature distribution. However, for coagulation therapy, detailed evaluation of the coagulated region is important. Therefore, a newly developed algorithm is presented for calculating the coagulated region within biological tissue. To confirm the validity of the proposed method, the calculated result is compared with the experimental findings. [ABSTRACT FROM PUBLISHER]

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\,\times\,0.8 mm\,\times \,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. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

This paper presented evaluation of electromagnetic (EM) energy absorption rate in terms of a specific absorption rate (SAR) in a fetus that was exposed to the EM wave from a portable radio terminal when used in the vicinity of the maternal abdomen. As for the numerical calculation, the electric fields around the antenna were analyzed by the finite-difference time-domain method. We considered analyzing six different positions of the antenna that are located around the waist. The SARs are normalized by 5-W radiated power from the antenna, which were a prevalent input power of wireless radio terminals in Japan. We confirmed that the SARs in the fetus are significantly affected by the distance and penetration path from the antenna to the surface on the fetus. Nonetheless, the SARs in the fetus are lower than the RF safety guidelines for occupational exposure in this paper. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

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 on body 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 on body 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. [ABSTRACT FROM AUTHOR]

Recently, research on medical applications of the thermal effects of microwaves, such as microwave treatment, on biological bodies has been carried out extensively. One example is hyperthermic treatment of cancer. In particular, in the treatment of cancer deep inside the human body, interstitial hyperthermia is effective. The most important characteristic of the antenna for interstitial hyperthermia is its heating properties. However, when clinical use is considered, impedance matching also must receive attention. In the present paper, with a view to impedance matching of the interstitial hyperthermia antenna, a coaxial slot antenna with a matching circuit of simple configuration is proposed. The reflection coefficient (S11) of the antenna is used as an evaluation guideline, and numerical simulation by the FDTD method and measurement are carried out. From these examinations, it is confirmed that the reflection characteristics can be improved drastically. It is further confirmed that the proposed antenna can supply a power of at least a certain level regardless of the electrical parameters of the biological tissue to be heated and of the antenna insertion length. Hence, this antenna is demonstrated to be practical. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(12): 11–19, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20218 [ABSTRACT FROM AUTHOR]

Microwave coagulation therapy (MCT) has been used mainly for the treatment of hepatocellular carcinoma (small cancer in the liver). In this therapy, a thin microwave antenna is inserted into the tumor. Using microwave radiation, the tumor is heated to a high temperature (at least 60 °C) and is killed by coagulation. In the MCT antenna used at present, there is the problem that the coagulation region is elongated along the antenna insertion direction so that the normal tissue around the tumor is also heated. It is desirable to heat the vicinity of the antenna tip in a spherical manner. In order to meet this requirement, a coaxial-dipole antenna is used and localized heating is realized. In this paper, first, by numerical analysis by the FDTD method and measurement of the SAR distribution, the usefulness of the coaxial-dipole antenna is demonstrated. Further, by computing the current distribution on the antenna, the reason for localization of the SAR by this antenna is studied. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(1): 16–23, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10049 [ABSTRACT FROM AUTHOR]

Hyperthermia is a cancer treatment that seeks to destroy cancer cells by heating. The authors have carried out analysis of coaxial-slot antennas as a hyperthermia heating device that uses microwaves. For characteristic evaluations of the hyperthermia heating device, the SAR (Specific Absorption Rate) as a value proportional to the square of the electric field near the antenna has been used widely. However, since hyperthermia seeks to heat cancer cells, it is desirable to know the temperature distributions inside actual biological bodies. In this paper, by means of the FDTD method, the SAR distribution around a coaxial-slot antenna in a biological body is computed. By solving the biological thermal transport equation with the SAR distribution as the heating source, the temperature distributions inside the biological body are computed. It is found that a hot spot can be generated due to the low thermal conductivity of the fat layer even if the coaxial-slot antenna used is an insertion-type antenna. As an application of this simulation, the temperature distributions are studied when the feed power of the antenna is on–off controlled. It is found that the uniformity of the temperature distribution inside the body is improved and the hot spot in the fat layer can be reduced. © 2001 Scripta Technica, Electron Comm Jpn Pt 2, 84(11): 20–29, 2001 [ABSTRACT FROM AUTHOR]

One of the treatments for cancer is hyperthermia, whereby the cancer cells are heated and killed by making use of the difference in thermal sensitivity of the cancer cells and normal cells. The authors have performed an analysis of the coaxial-slot antenna as a heating apparatus for microwave hyperthermia by means of a simulation by the method of moments. In this method, it was not possible to accurately evaluate the thermal profile on the surface of a lossy material, which is extremely important for evaluation of the heating characteristics of the antenna. Also, since the analysis model used assumed that the present antenna is inserted into a lossy material (muscle), it was not possible to evaluate the heating characteristics in multilayered media in an actual human body configuration. In the present paper, the FDTD analysis is introduced for the analysis of the coaxial-slot antenna. First, we ascertain what shape is appropriate for the analysis model. Using this information, the heating profile on the surface of a lossy material is obtained. Further, the heating characteristics when the present antenna is inserted into a multilayered medium simulating the human body are quantitatively determined. © 2000 Scripta Technica, Electron Comm Jpn Pt 1, 84(3): 48–55, 2001 [ABSTRACT FROM AUTHOR]