An EIT Inspired RFID Displacement Sensor for Metal Movement Monitoring

The cracks of weld seam are widely present. Owing to the complex geometry and environment of weld materials, there are challenges in health monitoring for cracks. Weld cracks affect the mechanical properties of the structure, and relative movement may occur when the base material bears loading. Based on the principle of strong coupling of electromagnetic-induced transparency (EIT), this paper proposes an UHF RFID wireless passive mi-crowave sensor with high sensitivity, which can detect and resolve deep sub-millimeter level displacement. A common dipole antenna structure is used to generate the bright mode, and a square split ring resonator (SSRR) structure is used to generate the dark mode, thus forming an EIT-like effect. This type of sensor is sensitive to the tiny displacement changes of the two modes and reflects in the frequency offset changes of the EIT window, which expected to achieve the highly sensitive movement monitoring in base metal.