A Highly Sensitive RFID Displacement Sensor Based on EIT-Like Effect

In this work, a wireless passive high-sensitivity displacement sensor operated in the ultra-high frequency (UHF) radio frequency identification (RFID) band is proposed for displacement monitoring. The sensor is designed based on the principle of electromagnetically induced transparency (EIT)-like effect, the strip dipole (SD) rendering a bright mode, and a pair of U-shaped ring resonators (USRR) producing a dark mode. The coupling between these two modes is extremely sensitive to micro displacement, enabling high-sensitivity displacement detection. The bright mode can directly capture the electromagnetic wave energy emitted by the RFID reader antenna and activate the RFID tag chip, enabling passive sensing. The resonant characteristics within the threshold power to activate the tag are utilized for displacement characterization, ensuring reliable wireless measurement. The proposed wireless passive displacement sensor has undergone simulation and experimental validation. The results indicate that the prototype sensor is capable of detecting displacement variations as small as 0.01 mm, consistently achieving deep sub-millimeter resolution, and demonstrating a detection sensitivity of 110 MHz/mm.