Charge Storage Level Indicator for RF Energy Harvester based on Dual-ID Passive UHF RFID Tag

Far-field RF energy harvesting is a convincing approach for energizing low-power wireless devices. In this work, we present a passive UHF RFID tag combined with an RF-energy harvester where a low-power switch circuitry changes the tag's ID as the voltage at the harvester's storage capacitor exceeds a certain threshold. This way, an RFID reader can receive the information on when the system is ready for running more advanced and energy-consuming functionalities. As a summary, our system switches the tag's ID as the voltage at the storage capacitor exceeds 0.7 V and our simulations predict that both tag IDs can be detected at the distance of more than 4.8 m while conforming to European UHF RFID emission regulations.