Phase Characterization of 1-200 MHz RF Signal Coupling with Human Body

To continuously monitor health information using wireless sensors placed on a person is a promising application. Human body communication (HBC) is proposed as a low power, security and light-weight communication technology that could be applied in aforementioned applications. In this work, the characterization of HBC propagation delay and phase deviation were investigated for the first time. In-situ experiments were performed in our lab in the frequency bands:1MHz-200MHz. Four HBC propagation channels, i.e., from left arm to right arm, from left arm to right leg, from right leg to left leg and from left arm to left leg were investigated. Group delay was measured from 13 volunteers, and then the propagation delay and phase deviation were estimated by statistical analysis. The propagation delay values are almost equal for four communication channels in each sub-band:1-100MHz and 100-200MHz. It is concluded that propagation delay is independent with propagation channel. However, from 1MHz to 100MHz the delay is generally longer than that in the frequency band 100-200MHz. i.e., in channel 1, the mean delay is 17.06 ns in frequency band 1-100MHz, while the mean delay is 15.23 ns in frequency band 100-200MHz. Lognormal model is found to be the best fitting distribution for the normalized phase deviation according the maximum likelihood estimation (MLE) and Akaike information criterion (AIC). Keywords-human body communication (HBC), propagation delay, phase deviation, statistical analysis