Powering Low-Power Wake-up Radios with RF Energy Harvesting

The deployment of connected devices in the context of the Internet of Things (IoT) is often constrained by battery capacity. To extend their operational lifespan, this thesis explores the use of Radio Frequency (RF) energy harvesting as an alternative power source for ultra-low-power Wake-up Radio (WuRx) devices. A WuRx enables IoT devices like wireless sensors to remain in deep sleep mode with minimal power consumption, waking them only when necessary. The first challenge is to design an RF energy harvesting circuit capable of providing regulated voltage from low RF power levels. An innovative solution is proposed, featuring an RF rectifier circuit with Schottky diodes and employing the inductive technique. This circuit sustains the operation of a power management circuit that subsequently powers a semi-active WuRx and stores RF energy efficiently when higher RF powers are available. Given the intermittent nature of RF energy, the second challenge is to adapt the energy consumption of the WuRx dynamically. We propose adjusting this consumption by modulating its quality of service, defined as the ratio of processed signals among all the received ones, based on the level of RF energy harvested in a battery. Integrating an RF harvester with a WuRx demonstrates the potential and viability of RF energy harvesting as a sustainable energy source for continuous listening devices in IoT deployments.