EM Simulation and Analysis on the Ground Electrode of Human Body Communication

Abstract

A plurality of mobile devices, such as cellular phones, PDAs, digital cameras and notebook computers, will be indispensable in ubiquitous environment. As more ubiquitous environment draws near, a more effective communication method that enables the plurality of mobile devices to communicate data is required. As one of the methods for data communication, the human body communication which uses a human body as a transmission medium has been proposed (Zimmerman, 1996). In the human body communication, a data from one device is transmitted to another device through human body. The human body communication has an advantage that the devices can communicate conveniently without an additional wire. A signal transmitter for human body communication has two electrodes: a signal electrode and a ground electrode. The signal electrode which is attached to human body feeds a transmitting signal into human body and the ground electrode is connected to the ground level of transmitter circuit. The signal loss is dependent on the fact that the ground electrode is attached to human body or not. The signal loss decreases as the ground electrode is attached to human body because the strength of electric field around human body increases and the imaginary value of load impedance of transmitter decreases (Fujii et al, 2003 and Fujii et al., 2002). In this paper, the measurement results on the effects of ground electrode according to the transmission distance are presented. A biological tissue-equivalent phantom has been used in the measurement of previous paper (Fujii et al., 2002), but a real human body is used in this paper. Also, the measurement results are analyzed by EM simulation. In the previous papers, the simulation model for human body has been composed of only muscle tissue. In this paper, more accurate model composed of muscle and other tissues is used during the simulation. Finally, the method by which a ground electrode can be used more efficiently is proposed based on the measurement results