Katsuyuki Fujii

Electric Field Distributions of Wearable Devices Using the Human Body as a Transmission Channel

Recently, wearable devices which use the human body as a transmission channel have been developed. However, there has been a lack of information related to the transmission mechanism of such devices in the physical layer. Electromagnetic communication trials using the human body as a transmission medium have more than a decades history. However, most of the researches have been conducted by researchers who just want to utilize the fact and practically no physical mechanisms have been researched until recently. Hence, in this paper, the authors propose some calculation models of the human body equipped with the wearable devices by using the finite difference time domain (FDTD) method. Moreover, a biological tissue-equivalent solid phantom is utilized to show the validity of the calculation. From these investigations, the authors determine the transmission mechanism of the wearable devices using the human body as a transmission channel.

Study on the Transmission Mechanism for Wearable Device Using the Human Body as a Transmission Channel

Recently, wearable devices which use the human body as a transmission channel have been developed. However, there has been a lack of information related the transmission mechanism of such devices in the physical layer. Electro-magnetic communication trials using human body as transmission media have more than a decades history. However, most of the researches have been conducted by researchers who just want to utilize the fact and practically no physical mechanisms have been researched until recently. Hence, in previous study, the authors proposed calculation models of the wearable transmitter and the receiver attached to the arm using the FDTD method. Moreover, the authors compared the calculated received signal levels to the measured ones by using a biological tissue-equivalent phantom. However, there was little analysis on each component of the propagated signal. In this paper, the authors clarified the transmission mechanism of the wearable device using the human body as a transmission channel from the view point of the interaction between electromagnetic wave and the human body. First, the authors focused their attention on measuring the each component of the propagated signal using a shielded loop antenna. From these results, the favorable direction of electrodes of the transmitter was proposed to use the human body as a transmission channel. As a result, longitudinal direction is effective for sending the signal to the receiver, compared to the transversal direction. Next, the authors investigated the dominant signal transmission channel, because the question of whether the dominant signal channel is in or around the arm had remained unsettled. To clear this question, the authors proposed the calculation model of an arm wearing the transmitter and receiver placed into a hole of a conductor plate. The electric field distribution and received signal voltage was investigated as a function of the gap between the hole of the conductor plate and the surface of the arm. The result indicated that the dominant signal transmission channel is not inside but the surface of the arm because signal seems to be distributed as a surface wave.

A study on the receiving signal level in relation with the location of electrodes for wearable devices using human body as a transmission channel

Studies of wearable computers have attracted public attention in these days And one of the area of interest is the communication system adopted in those wearable computers. As an example, wear-able devices which use the human body as a transmission channel, have been developed. This communication system uses near field region of the electromagnetic wave generated by the device which is eventually coupled to human body by electrodes. Hence, the structure of electrodes is one of the key issues for the transmission using human body. However, little is known about the transmission mechanism of such devices in the physical layer. In this paper, we propose calculation models of the transmitter and the receiver attached to the arm using the FDTD method. From this model, we estimated the difference in the received signal level due to the electrode structures of the transmitter and the receiver under various conditions. Moreover, in order to verify the validity of these calculation models, we compared the calculated received signal levels to the measured ones by using the biological tissue-equivalent phantom with die transmitter and the receiver. The result shows a good agreement of the calculated and measured received signal levels. In addition, it is found that the GND electrode of the transmitter strengthens the generated electric field around the ann. However, the existence of a GND electrode for the receiver reduces the received signal level.

Evaluation of the received signal level in relation to the size and carrier frequencies of the wearable device using human body as a transmission channel

Studies of wearable computers have attracted public attention these days. One of the area of interest is the communication system adopted in those wearable computers. As an example, wearable devices which use the human body as a transmission channel have been developed. When a user wearing the transmitter touches the electrode of the receiver, a transmission channel is formed within the human body. In this paper, investigations of the received signal level in relation with the carrier frequency and the size of the transmitter using human body as a transmission channel have been presented. The results show that the received signal voltage is slightly influenced by using higher frequency from 10 MHz to 100 MHz in the ISM frequency bands. However, it strongly depends on the size of the transmitter. In addition, it is necessary that the direction of the electrode of the transmitter is transverse for higher received signal level, compared with the longitudinal direction.

Study on the electric field distributions around whole body model with a wearable device using the human body as a transmission channel

In the near future, we will begin to attach wearable devices, and we will meet the ubiquitous computing society in Weiser, M. However, currently there are little methods for these personal devices to exchange data directly. We want to exchange the data of the wearable devices without physical constraint like an external wire connection that may easily be tangled. The solution for networking these personal devices has been proposed as Personal Area Networks (PANs) which uses the human body as a transmission channel in Zimmerman, T.G., et al, (1995). Many studies have been made on the development of such devices so far, however, most of the researches have been conducted by researchers who just want to utilize the fact and practically a little physical mechanisms have been researched until recently by Fukumoto, M., et al, (1997). In this paper, the authors clarify the electromagnetic field distributions of the near-field intrabody communication devices from the view point of the interaction between the electromagnetic wave and the human body by using the FDTD method. In the FDTD calculation, a realistic high resolution whole-body model of Japanese adult male with average height and weight in Nagaoka, T., et al, (2004) is used, because there has been little study that tried to clarify the electromagnetic field distributions around the full scale human body with the wearable devices. Moreover, simple block model of the whole body is introduced, and electric field distribution of the simple body is compared to that of the realistic one. Moreover, we demonstrate the electric field distributions around simple whole body when the positions are changed.

Development and Investigation of the Transmission Mechanism of the Wearable Devices Using the Human Body as a Transmission Channel

INTRODUCTION As cellular phones, personal digital assistants (PDAs), pocket video games, and other information and communication devices become smaller and more widespread, we have begun to adorn our bodies with these appliances and the opportunities to use these small computers have been increased in our everyday lives. We can say with fair certainty that miniaturization of these devices will evolve, and we will meet the ubiquitous computing society [1]. However, currently there is no method for these personal devices to exchange data directly. If these devices are wire-connected, it is clearly impractical because they easily become tangled, so some sort of short-range wireless technology is required. The concept for networking these personal devices has been proposed as Personal Area Networks (PANs) which use the human body as a transmission channel [2]. Although many studies have been made on the development of wearable devices using the human body as a transmission channel, little is known about the transmission mechanism of such devices in the physical layer [2]-[8]. Figs. 1 3 show a few examples of communication systems of the PANs [5]. When a user wearing the transmitter touches the electrode of the receiver, a transmission channel is formed using the human body. In this case, the receiver recognizes the users ID and it can be personalized. The merit of this system is that the data is exchanged through daily natural actions, such as simply touching the receiver. This communication system uses the near field region of the electromagnetic wave generated by the device which is eventually coupled to the human body by electrodes. Hence, the structure of electrodes is one of the key issues for the transmission using human body. The difference of the transmission power caused by the electrode structure needs to be considered in detail.

Effect of Earth Ground and Environment on Body-Centric Communications in the MHz Band

Body area network (BAN) research, which uses the human body as a transmission channel, has recently attracted considerable attention globally. Zimmerman first advocated the idea in 1995. Illustrations of the electric field streamlines around the human body and wearable devices with electrodes were drawn. In the pictures, the electrodes of the wearable devices constitute a closed circuit with the human body and the earth ground. However, analysis of the circuit has not been conducted. In this study, we model the human body shunted to earth ground in a radio anechoic chamber to analyze the electric field strength around it and clarify the effect of earth ground during BAN run time. The results suggest that earth ground has little influence on the human body and wearable devices. Only when the human body is directly grounded, the electric field near the feet area will decrease. The input impedance of the transmitter is approximately the same, and the received open-circuit voltage and current of the receiver are also the same. In addition, we elucidate that stable communications can be established by developing a closed circuit using earth ground as return path. When the external electronic devices and human body are shunted to earth ground, the received open-circuit voltage and current increase.

Study on the electromagnetic field distributions of realistic Japanese adult male and female models with a wearable device using the human body as a transmission channel

In this paper, the electric field distribution of the human body with the wearable device using the human body as a transmission channel was discussed. For the calculation, the realistic high resolution whole-body model of Japanese adult male and female with average height and weight is used. As a result, most part of the electric field is concentrated around the tip of the arm, so the transmission system using the human body as a transmission channel has advantage for the practical use. Because one of the merits of this system is that data can be exchanged by our daily natural actions, such as simply touching the receiver, and the user can be clearly aware of connection

ANALYTICAL AND EXPERIMENTAL MODELING OF INTRA-BODY COMMUNICATION CIRCUIT

ABSTRACT Intra-body communication uses human body as the propagation medium. This may become a new wireless communication method for Personal Area Network (PAN) with less power consumption and higher communication security compared to conventional RF methods. A common analytical model of intra-body communication is a combination of capacitive coupling among the human body, electronic devices, and the environment. Experimental results suggest that there are optimal parameters for transmission. We assume that it is a combination of not only the capacitive couplings, but also of a radio wave transmission and of imbalances in the electrical impedances among the transmitter/receiver electrodes attached to the human body.