Novel pair electrode with coils sensing magnetic energy on human body surface for intrabody communication

The spread of small mobile terminals, such as cell phones, is spurring interest in Wireless Body Area Network (WBAN), including intrabody communication utilizing electromagnetic field on human body surface. In order to generate or detect the change in the EM field on human body surface, intrabody communication usually utilizes a pair electrode, instead of antenna. The pair electrode consists of a signal electrode and a ground (GND) electrode. When the signal electrode is in contact with human body surface or is close to human body surface, capacitive coupling occurs between the signal electrode and human body surface. Through the capacitive coupling, the electrode can transmit or receive electromagnetic wave on human body surface. The capacitive coupling decreases in proportion to the distance between the signal electrode and human body surface. As a result, the power received by the receiver degrades. In most research on intrabody communication, the signal electrode is in contact with human body surface. There are few reports on improvement of the received power. An electric-field sensor implemented with a transverse EO sensor is used to improve the received power. However, the EO sensor is so costly that other countermeasure is demanded to improve the received power. In this paper, the authors propose a new method in which bar antennas employed with pair electrode acting as variable capacitance is implemented in order to improve the received power when the signal electrode is not in contact with human body surface.