Figure 4

Inter-body coupling modes for Capacitive HBC users: (a) EQS Region, \(\hbox {f}<1 \,\hbox {MHz}\), capacitive coupling dominates. (b) \(1 \,\hbox {MHz}<\hbox {f}<10 \,\hbox {MHz}\), body starts to act as a small monopole antenna, giving a 40dB/decade rising response in coupling. (c) \(10 \,\hbox {MHz}<\hbox {f}<100 \,\hbox {MHz}\), wavelength comparable to body dimensions; Body-antenna resonance peaks occur. (d) \(\hbox {f}>100 \,\hbox {MHz}\), wavelength comparable to device dimensions; the devices start coupling through EM leakage. (e) The trend of maximum distance, over which signals from inter-body coupling can be detected (for a fixed SNR at the transmitter), over frequency. The distance limit is low independent of frequency for EQS coupling, increases rapidly once the two bodies start becoming efficient antennas, and becomes saturates once the devices become efficient antennas themselves.