Biophysical Circuit Modeling of Electro-Quasistatic Multi-Human Body Communication

Human body communication, particularly of the Electro-Quasistatic variety, has gained traction among low-power wireless circuit designers due to its benefits in terms of power and physical security compared to conventional electromagnetic or radio frequency communication. Yet, applying its theory and practice has thus far been limited to a single person, without a clear understanding of how the channel behaves when multiple individuals or human bodies are added. To the author's knowledge, this work analyzes the limit of the quasistatic approximation in a multiple human body scenario for the first time. It demonstrates how the approximation changes with the length scale. Furthermore, the channel gain for varying numbers of human bodies is measured to be -35 dB (one human body), -41 dB (two humans), and -44 dB (three humans) for a ground-connected transmitter. A complete bio-physical circuit model is generated to accurately predict the voltage received on the quasi-static structure depending on how many human bodies are connected serially. The impact of the work can aid designers in realizing applications in secure key exchange, authentication, and music sharing using electro-quasistatic human body communication techniques.