Input impedance characteristics of wearable transmitter electrodes for intra-body communication

Intra-body communication draws attention as a promising wireless technology in order to materialize wireless body-centric networks. An electrode in intra-body communication system is a key device since the electrodes are analogous to antennas in airborne wireless communication system. However, nobody has addressed the broadband input impedance characteristics of the electrodes although there are a few study reports discussing them at one single frequency. In this paper, the input impedance characteristics of the wearable transmitter electrodes in the frequency range of 500 kHz to 1 GHz, and the electromagnetic field distributions around and inside the human arm at the frequency of 10 MHz were investigated. As a result, both magnitudes of the resistive and reactive components of the input impedance increased as frequency increased below 200 MHz. Further, it was also found that the electric field was strongly distributed only the vicinity of the human arm with a transmitter. It could be advantageous in the view points of the high-secured communication and the electromagnetic compatibility (EMC).