Variation of impedance in transmission channel of human body communication

Human body communication (HBC) is a wireless communication method that uses human body as part of the transmission medium. It uses electrodes instead of antennas to generate electric field around the human body. This electric field forms capacitive couplings between transmitter, receiver, human body, and surrounding environment. Transmission from a transmitter on user's wrist to an off-body receiver touched by the user was investigated. The human body wearing a transmitter was modeled as a signal source connected to the receiver input. The equivalent output impedance is composed of impedance of the human body and the capacitance of the capacitive coupling that is affected by the surrounding environment and the transmitter arrangement. Equivalent output impedance was estimated by maximizing the received signal power by adjusting input resistance of the receiver and by inserting inductance. Three types of transmitter electrodes and two types of receiver stands (wood and steel) were used to evaluate influences on the equivalent output impedance.