Self-Sustainable Long-Range Backscattering Communication Using RF Energy Harvesting

Radio-frequency (RF)-powered backscattering communication (BC) has many advantages, such as low-power consumption, battery-free, small size, low cost, full sealing, manual maintenance-free, and easy mass deployment. However, the weak RF energy harvested and the short BC distance have become the two critical obstacles in the real-world implementation of this potential technology. In this article, we propose a high-sensitivity RF energy harvesting (RFEH) and long-distance BC method, and for the first time, we demonstrate the RF-powered self-sustainable long-distance BC device named RFEH LoRa. In order to improve RFEH sensitivity, an ultralow-power (ULP) consumption voltage monitoring and startup control circuit topology is designed to reduce the power consumption to 245 nanowatt (nW) during the accumulation of RF energy. While in order to increase the BC distance, a direct digital frequency synthesis technology is used to generate a linear frequency modulation square wave sequence conforming to the LoRa specifications based on the ULP microcontroller unit, and the square wave is used to drive an RF switch to achieve long-distance BC of hundreds of meters. Test results show that the instantaneous BC current is as low as 130 microampere ( ${\mu }\text{A}$ ), and the standby current is only 52 nanoampere (nA). RFEH LoRa is implemented with commercial off-the-shelf components. It can self-startup by harvesting RF energy as low as −22.5 dBm, and send its sensing data to the receiver of 381-m away.