Energy Autonomous Dual-Band Antenna System for RFID-Based Real-Time Battery Level Monitoring

Abstract

This paper presents an energy-autonomous antenna system that combines energy harvesting (EH) with radio frequency identification (RFID) communication to measure the battery charge level in real time. The system employs a dual-band patch antenna, a dual-band matching stub, and a diplexer, which are designed with metamaterial-based electromagnetic bandgap technology (MTM-EBG). Due to the MTM-EBG’s uniplanar and via-less design, it can be directly embedded into the antenna and microstrip feed components, thereby contributing to their compactness, lowering cost, and simplifying fabrication. The RFID and EH portions of the system operate at frequencies of 915 MHz and 2.48 GHz, respectively. This system operates by rectifying RF power in the EH band in order to charge a supercapacitor battery, while a varactor imparts phase to the backscattered RFID signal. The phase of reflection is related to the level of charge in the battery, which is then read by the RFID reader. By acquiring the tag and charging information without power, this structure is energy autonomous, so there is no need for a permanent power source that will need to be replaced over time. Using supercapacitors or rechargeable batteries, the proposed structure can provide power for critical functions while monitoring their charging status remotely. The antenna system and RFID/EH architecture have been fabricated and measured, and battery level monitoring has been demonstrated.