EQS Res-HBC: A 65-nm Electro-Quasistatic Resonant 5–240 μW Human Whole-Body Powering and 2.19 μW Communication SoC With Automatic Maximum Resonant Power Tracking

Abstract

Applications like connected healthcare through physiological signal monitoring and secure authentication using wearable keys can benefit greatly from the battery-less operation. Low-power communication along with energy harvesting is critical to sustain such perpetual battery-less operation. Human body channel is known to be a promising alternative to wireless radio wave communication for low power operation through human body communication (HBC), as well as very recently demonstrated as a medium for power transfer through body-coupled power transfer. However, channel length (L) dependency of the received power makes it inefficient for L>40 cm. In this article, we utilize electro-quasistatic resonant HBC (EQS Res-HBC) with maximum resonant power tracking (MRPT) to enable channel length-independent whole-body communication and powering. We design the first system to transfer power and data from a HUB device to wearable energy-harvested NODE through the human body to enable battery-less perpetual operation. Measurement results show 240, 28, and 5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> power transfer through the body in a machine–machine (large devices with strong ground connection), tabletop (small devices kept on a table), and wearable–wearable (small form factor battery-operated wearable devices) scenario, respectively, independent of body channel length, while enabling communication at 2.19 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> . This enables >25 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> more power transfer with >100 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> more efficiency compared to the state of the art for 100-cm body channel in tabletop scenario by utilizing the benefits of EQS operation. The MRPT loop automatically tracks device and posture-dependent changes in the resonance point to maximize power transfer in all cases.