Transcatheter renal denervation (RDN) is a treatment for resistant hypertension, which is performed by ablating the renal nerves located outside the artery using a catheter from inside the artery. Our previous studies simulated the temperature during RDN by using constant physical properties of biological tissue to validate the various catheter RDN devices. Some other studies report temperature dependence of physical properties of biological tissues. However, there are no studies that have measured the electrical properties of low water content tissues. Adipose tissue, a type of low water content tissue, is related to RDN closely. Therefore, it is important to know the temperature dependence of the electrical constants of adipose tissue. In this study, we measured the relationship between the electrical constants and the temperature of bovine adipose tissue. Next, the obtained equation of the relationship between relative permittivity of adipose tissue and temperature was introduced. In addition, the temperature dependence of the electrical constants of high water content tissues and the temperature dependence of the thermal constants of biological tissues were also introduced into the temperature analysis. After 180 seconds of heating, the temperature of the model with the temperature dependence of the physical properties was 7.25°C lower than the model without the temperature dependence of the physical properties at a certain position. From the results, it can be said that the temperature dependence of physical properties will be significant when an accurate temperature analysis is required.

The Doppler velocity enhanced 79 GHz band millimeter wave (MMW) radar imaging approach is presented here, assuming a human body imaging or recognition application. There are numerous situations in which the spatial resolution is insufficient, due to aperture angle limitations, especially for vehicle mounted MMW radar systems. As the 79 GHz band MMW radar has a definitive advantage for higher Doppler velocity resolution even with a short coherent processing interval (CPI), this study introduces the Doppler velocity decomposed imaging scheme, focusing on micro-Doppler variations of the walking human model. The real experimental data show that our proposed approach provides further improvement for accurate and high resolution radar imaging.

In recent years, microwave wireless power transfer (WPT) has attracted considerable attention due to the increasing demand for various sensors and Internet of Things (IoT) applications. Microwave WPT requires technology that can detect and avoid human bodies in the transmission path. Using a phantom is essential for developing such technology in terms of standardization and human body protection from electromagnetic radiation. In this study, a simple and lightweight phantom was developed focusing on its radar cross-section (RCS) to evaluate human body avoidance technology for use in microwave WPT systems. The developed phantom's RCS is comparable to that of the human body.

We developed an 8.4-inch electrostatic-tactile touch display using a segmented-electrode array (30×20) as both tactile pixels and touch sensors. Each pixel can be excited independently so that the electrostatic-tactile touch display allows presenting real localized tactile textures in any shape. A driving scheme in which the tactile strength is independent of the grounding state of the human body by employing two-phased actuation was also proposed and demonstrated. Furthermore, tactile crosstalk was investigated to find it was due to the voltage fluctuation in the human body and it was diminished by applying the aforementioned driving scheme.

This paper describes the effectiveness of the geometric multi-grid method in a current density analysis using a numerical human body model. The scalar potential finite difference (SPFD) method is used as a numerical method for analyzing the current density inside a human body due to contact with charged objects in a low-frequency band, and research related to methods to solve faster large-scale simultaneous equations based on the SPFD method has been conducted. In previous research, the block incomplete Cholesky conjugate gradients (ICCG) method is proposed as an effective method to solve the simultaneous equations faster. However, even though the block ICCG method is used, many iterations are still needed. Therefore, in this study, we focus on the geometric multi-grid method as a method to solve the problem. We develop the geometric-multi-grid method and evaluate performances by comparing it with the block ICCG method in terms of computation time and the number of iterations. The results show that the number of iterations needed for the geometric multi-grid method is much less than that for the block ICCG method. In addition, the computation time is much shorter, depending on the number of threads and the number of coarse grids. Also, by using multi-color ordering, the parallel performance of the geometric multi-grid method can be greatly improved.

This paper reviews our developed wide band human body communication technology for wearable and implantable robot control. The wearable and implantable robots are assumed to be controlled by myoelectric signals and operate according to the operator's will. The signal transmission for wearable robot control was shown to be mainly realized by electrostatic coupling, and the signal transmission for implantable robot control was shown to be mainly determined by the lossy frequency-dependent dielectric properties of human body. Based on these basic observations on signal transmission mechanisms, we developed a 10-50MHz band impulse radio transceiver based on human body communication technology, and applied it for wireless control of a robotic hand using myoelectric signals in the first time. In addition, we also examined its applicability to implantable robot control, and evaluated the communication performance of implant signal transmission using a living swine. These experimental results showed that the proposed technology is well suited for detection and transmission of biological signals for wearable and implantable robot control.

This paper proposes a path loss model for crowded outdoor environments that can consider the density of people. Measurement results in an anechoic chamber with three blocking persons showed that multiple human body shadowing can be calculated by using finite width screens. As a result, path loss in crowded environments can be calculated by using the path losses of the multipath and the multiple human body shadowing on those paths. The path losses of the multipath are derived from a ray tracing simulation, and the simulation results are then used to predict the path loss in crowded environments. The predicted path loss of the proposed model was examined through measurements in the crowded outdoor station square in front of Shibuya Station in Tokyo, and results showed that it can accurately predict the path loss in crowded environments at the frequencies of 4.7GHz and 26.4GHz under two different conditions of antenna height and density of people. The RMS error of the proposed model was less than 4dB.

This paper presents the bit error rate (BER) performance of human body communication (HBC) receivers in interference-rich environments. The BER performance was measured while applying an interference signal to the HBC receiver to consider the effect of receiver performance on BER performance. During the measurement, a signal attenuator was used to mimic the signal loss of the human body channel, which improved the repeatability of the measurement results. The measurement results showed that HBC is robust against the interference when frequency selective digital transmission (FSDT) is used as a modulation scheme. The BER performance in this paper can be effectively used to evaluate a communication performance of HBC.

The radio wave shadowing by a two-dimensional human body is examined numerically as the scattering problem by using the Method of Moments (MoM) in order to verify the equivalent human body diameter. Three human body models are examined: (1) a circular cylinder, (2) an elliptical cylinder, and (3) an elliptical cylinder with two circular cylinders are examined. The scattered fields yields by the circular cylinder are compared with measured data. Since the angle of the model to an incident wave affects scattered fields in models other than a circular cylinder, the models of an elliptical cylinder and an elliptical cylinder with two circular cylinders are converted into a circular cylinder of equivalent diameter. The frequency characteristics for the models are calculated by using the equivalent diameter.

In recent years, multiple-input multiple-output (MIMO) channel models for crowded areas, such as indoor offices, shops, and outdoor hotspot environments, have become a topic of significant interest. In such crowded environments, propagation paths are frequently shadowed by moving objects, such as pedestrians or vehicles. These shadowing effects can cause time variations in the delay and angle-of-arrival (AoA) characteristics of a channel. In this paper, we propose a method for modeling the shadowing effects of pedestrians in a cluster-based channel model. The proposed method uses cluster power variations to model the time-varying channel properties. We also propose a novel method for estimating the cluster power variation properties from measured data. In order to validate our proposed method, channel sounding in the 3GHz band is conducted in a cafeteria during lunchtime. The results for the K parameter, delay spreads, and AoA azimuth spreads are compared for the measured data and the channel data generated using the proposed method. The results indicate that the time-varying delay-AoA characteristics can be effectively modeled using our proposed method.

This paper proposes the use of two transmit and two receive antennas spaced at roughly the width of a human body to improve communication quality in the presence of shadowing by a human body in the 60GHz band. In the proposed method, the transmit power is divided between the two transmit antennas, and the receive antenna that provides the maximum receive level is then chosen. Although the receive level is reduced by 3dB, the maximum attenuation caused by human body shadowing is totally suppressed. The relationship between the antenna element spacing and the theoretical spacing based on the 1st. Fresnel zone theory is clarified. Experiments confirm that antenna spacing several centimeters wider than that given by the 1st. Fresnel zone theory is enough to attain a significant performance improvement.

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.

This paper presents a method of imaging a two-dimensional section of a walking person using multiple Doppler radar systems. Although each simple radar system consists of only two receivers, different radial speeds allow target positions to be separated and located. The signal received using each antenna is processed employing time-frequency analysis, which separates targets in the time-range-velocity space. This process is followed by a direction-of-arrival estimation employing interferometry. The data obtained using the multiple radar systems are integrated using a clustering algorithm and a target-tracking algorithm. Through realistic simulations, we demonstrate the remarkable performance of the proposed imaging method in generating a clear outline image of a human target in unknown motion.

In this paper, we propose a simple model for estimating the effects of human body shadowing (HBS) in high frequency bands. The model includes two factors: the shadowing width (SW), which is the width of the area with shadowing loss values greater than 0dB, and the median shadowing loss value (MSLV), which is obtained by taking the median of the shadowing loss values within the SW. These factors are determined by formulas using parameters, i.e. frequency, distance between the base station (BS) and human body, distance between the terminal and human body, BS antenna height, and direction of the human body. To obtain the formulas, a method for calculating the effects of HBS based on the uniform theory of diffraction (UTD) and a human body model comprising lossy dielectric flat plates is proposed and verified. Then, the general forms of the formulas are predicted using the theory of knife-edge diffraction (KE). A series of computer simulations using the proposed calculation method with random changes in parameters is conducted to verify the general formulas and derive coefficients for these formulas through regression formulas.

This paper describes a very accurate method of estimating the return-path-capacitance and validates the estimation based on low-error measurements for electric-field intrabody communication. The return-path capacitance, Cg, of a mobile transceiver is estimated in two ways. One uses the attenuation factor in transmission and capacitance, Cb, between a human body and the earth ground. The other uses the attenuation factor in reception. To avoid the influence of the lead wire in the estimation of Cb, Cb is estimated from the attenuation factor measured with an amplifier with a low input capacitance. The attenuation factor in reception is derived by using the applied-voltage dependence of the reception rate. This way avoids the influence of any additional instruments on the return-path capacitance and allows that capacitance to be estimated under the same condition as actual intrabody communication. The estimates obtained by the two methods agree well with each other, which means that the estimation of Cb is valid. The results demonstrate the usefulness of the methods.

In recent years, there has been rapid developments in radio-frequency identification (RFID) systems, and their industrial applications include logistics management, automatic object identification, access and parking management, etc. Moreover, RFID systems have also been introduced for the management of medical instruments in medical applications to improve the quality of medical services. In recent years, the combination of such a system with a biological monitoring system through permanent implantation in the human body has been suggested to reduce malpractice events and ameliorate the patient suffering. This paper presents an implantable RFID tag antenna design that can match the conjugate impedance of most integrated circuit (IC) chips (9.3-j55.2Ω at 2.45GHz. The proposed antenna can be injected into the human body through a biological syringe, owing to its compact size of 9.3mm × 1.0mm × 1.0mm. The input impedance, transmission coefficient, and received power are simulated by a finite element method (FEM). A three-layered phantom is used to confirm antenna performance.

We propose a novel and efficient approach for tracking 2D articulated human body parts. In our approach, the human body is modeled by a graphical model where each part is represented by a node and the relationship between a pair of adjacent parts is indicated by an edge in the graph. Various approaches have been proposed to solve such problems, but efficiency is still a vital problem. We present a new Quick Shift Belief Propagation (QSBP) based approach which benefits from Quick Shift, a simple and efficient mode seeking method, in a part based belief propagation model. The unique aspect of this model is its ability to efficiently discover modes of the underlying marginal probability distribution while preserving the accuracy. This gives QSBP a significant advantage over approaches like Belief Propagation (BP) and Mean Shift Belief Propagation (MSBP). Moreover, we demonstrate the use of QSBP with an action based model; this provides additional advantages of handling self-occlusion and further reducing the search space. We present qualitative and quantitative analysis of the proposed approach with encouraging results.

Electrostatic discharge (ESD) events due to metal objects electrified with low voltages give a fatal electromagnetic interference to high-tech information equipment. In order to elucidate the mechanism, with a 6-GHz digital oscilloscope, we previously measured the discharge current due to collision of a hand-held metal piece from a charged human body, and gave a current calculation model. In this study, based on the calculation model, a method was presented for deriving a gap potential gradient from the measured discharge current. Measurements of the discharge currents were made for charge voltages from 200 V to 1000 V. The corresponding potential gradients were estimated, which were validated in comparison with an empirical formula based on the Paschen's law together with other researcher's experimental results.

Wireless communication devices in the field of medical implant, such as cardiac pacemakers and capsule endoscopes, have been studied and developed to improve healthcare systems. Especially it is very important to know the range and position of each device because it will contribute to an optimization of the transmission power. We adopt the time-based approach of position estimation using ultra wideband signals. However, the propagation velocity inside the human body differs in each tissue and each frequency. Furthermore, the human body is formed of various tissues with complex structures. For this reason, propagation velocity is different at a different point inside human body and the received signal so distorted through the channel inside human body. In this paper, we apply an adaptive template synthesis method in multipath channel for calculate the propagation time accurately based on the output of the correlator between the transmitter and the receiver. Furthermore, we propose a position estimation method using an estimation of the propagation velocity inside the human body. In addition, we show by computer simulation that the proposal method can perform accurate positioning with a size of medical implanted devices such as a medicine capsule.

The medical care day by day and more and more is associated with and reliant upon concepts and advances of electronics and electromagnetics. Numerous medical devices are implanted in the body for medical use. Tissue implanted devices are of great interest for wireless medical applications due to the promising of different clinical usage to promote a patient independence. It can be used in hospitals, health care facilities and home to transmit patient measurement data, such as pulse and respiration rates to a nearby receiver, permitting greater patient mobility and increased comfort. As this service permits remote monitoring of several patients simultaneously it could also potentially decrease health care costs. Advancement in radio frequency communications and miniaturization of bioelectronics are supporting medical implant applications. A central component of wireless implanted device is an antenna and there are several issues to consider when designing an in-body antenna, including power consumption, size, frequency, biocompatibility and the unique RF transmission challenges posed by the human body. The radiation characteristics of such devices are important in terms of both safety and performance. The implanted antenna and human body as a medium for wireless communication are discussed over Medical Implant Communications Service (MICS) band in the frequency range of 402-405 MHz.