Charging and Wake-Up of IoT Devices using Harvested RF Energy with Near-Zero Power Consumption

Sixth generation (6G) wireless systems are envisioned to support ubiquitous connection of a massive number of battery-powered Internet-of-Things (IoT) devices. Radio frequency (RF) energy harvesting and wake-up radio have been extensively considered as standalone technologies to extend the battery lifetime of IoT devices. In this article, we present a general framework for designing efficient combined RF energy harvesting and wake-up circuits to further reduce the energy consumption of IoT devices and allow them to operate nearly self-sustainably. Specifically, we propose two address detector designs: a dual-power-mode pulse width detector (PWD) and a multi-power-mode pulse width modulation (PWM) detector that can be integrated in combined architectures with a single shared antenna and rectifier. Furthermore, we validate the practicality of the presented framework by testing sample designs under real operational conditions. Finally, we conclude the article by introducing future research directions for realizing large IoT networks with combined RF energy harvesting and wake-up radio.