Robust Communication and Power Transfer Over a Single Loosely Coupled Inductive Link for Miniaturized and Batteryless Sensing Devices

This paper presents an innovative dual-mode system as well as design techniques to realize full-duplex data communication and wireless power transfer over a single inductive link. An LC tank implemented on a compact printed circuit board is shared between a rectifier that supplies the batteryless device and a power oscillator that modulates the uplink data in a time division duplex fashion. Designed to operate efficiently in the loose coupling regime, the proposed design ensures reliable performance over a substantial distance and is resilient to interference from the wireless power transfer signal. A miniaturized prototype is implemented on a printed circuit board package with a diameter of 19 mm, which is powered by a 180-nm CMOS chipset. At a data rate of 10 kbps, the coin-sized prototype achieves powering and uplink distances of 140 mm and 110 mm, respectively, offering a fivefold improvement in normalized operating range compared to recent single-coil designs of similar size. The performance of the proposed sensing device is verified by inserting a thick biological tissue between the coils and recording ex-vivo biopotential signals.