Ultra-low Power Wake-up Receivers for IoT Devices with Application to Smart Agriculture

Abstract

Radio Frequency (RF) energy harvesting has been proposed as a solution to power the increasing number of Internet-of-Things (IoT) devices. Exploiting this energy source is challenging because RF signals attenuate quickly. Therefore, a solution must be found to minimize the power consumption of the numerous devices relying on harvested RF energy. RF wake-up is a mechanism that is employed to reduce the power consumption of IoT devices by switching them ON only when they are required to operate. This solution requires an RF wake-up receiver to process an external wake-up signal. Wake-up receivers have a strict power consumption requirement and, therefore, must maintain a simple architecture, while being able to detect a targeted wake-up signal.

In this work, we design an address detector for an RF wake-up receiver that uniquely identifies a sensor through an address that we encode in the detector's hardware. The proposed architecture is optimized for situations where an antenna is used for harvesting and wake-up. We propose a multi-power-state design to power the minimal components required to process a wake-up signal and minimize power consumption. We integrate our solution with a rectifier and Power Management Unit (PMU) to perform both RF harvesting and wake-up using the same antenna and rectifier. Further, we implement the system in an IoT smart agriculture application where wake-up signals are transmitted to control the operation of sensors using commercial routers. We study the efficacy of using UAVs as a transmitter to cover large agricultural fields. Our results show that implementing wake-up and harvesting can extend the lifetime of agricultural sensors that span large areas and communicate via wireless transceivers. Finally, we support our work with detailed experimental results and analysis.