Effect of nearby Metals on Electro-Quasistatic Human Body Communication

In recent decades Human Body Communication has emerged as a promising alternative to traditional radio wave communication, utilizing the body's conductive properties for low-power connectivity among wearables. This method harnesses the human body as an energy-efficient channel for data transmission within the electro-quasistatic frequency range, enabling advancements in human-machine interaction. While prior work has noted the role of parasitic return paths in such capacitively coupled systems, the influence of surrounding metallic objects on these paths, which are critical for EQS wireless signaling, has not been fully explored. This paper fills that gap with a structured study of how various conducting objects, from non-grounded (floating) metals and grounded metals to enclosed metallic environments such as elevators and cars, affect the body-communication channel. We present a theoretical framework supported by finite element method simulations and experiments with wearable devices. Results show that metallic objects within 20 cm of devices can reduce transmission loss by about 10 dB. When a device ground connects to a grounded metallic object, channel gain can increase by at least 20 dB. Contact area during touch-based interactions with grounded metals produces contact-impedance dependent high-pass channel characteristics. Proximity to metallic objects introduces variability within a critical distance, with grounded metals producing a larger overall effect than floating metals. These findings improve understanding of body-centric communication links and inform design for healthcare, consumer electronics, defense, and industrial applications.

Body-Resonance Human Body Communication

Seamless interaction between Humans and AI-empowered battery-operated miniaturized electronic devices, exponentially transforming the wearable technology industry while forming an anthropomorphic artificial nervous system for distributed computing around the human body, demands high-speed low-power connectivity. If interconnected via radio frequency (RF) based wireless communication techniques, that being radiative, incur substantial absorption losses from the body during non-line-of-sight scenarios and consume higher power (more than 10s of mW). Although as a promising alternative with its non-radiative nature that resulted in 100X improvement in energy efficiency (sub-10 pJ/bit) and better signal confinement, Electro-Quasistatic Human Body Communication (EQS HBC) incurs moderate path loss (60-70 dB), limited data rate (less than 20 Mbps), making it less suitable for applications demanding fast connectivity like HD audio-video streaming, AR-VR-based products, distributed computing with wearable AI devices. Hence, to meet the requirement of energy-efficient connectivity at 100s of Mbps between wearables, we propose Body-Resonance (BR) HBC, which operates in the near-intermediate field and utilizes the transmission-line-like behavior of the body channel to offer 30X improvement in channel capacity. Our work sheds new light on the wireless communication system for wearables with potential to increase the channel gain by 20 dB with a 10X improvement in bandwidth compared to the EQS HBC for communication over on-body channels (whole-body coverage area). Experimentally demonstrating BR HBC, we presented low-loss (40-50 dB) and wide-band (hundreds of MHz) body channels that are 10X less leaky than radiative wireless communication, hence, can revolutionize the design of wireless communication system for several applications with wearables from healthcare, defense, to consumer electronics.