Electromagnetic characterization of passive RFID crack sensor based on symmetric semicircular ring structure

In this paper, a structural health monitoring (SHM) sensor based on passive radio frequency identification (RFID) technology is designed. The sensor utilizes a Taconic CER substrate consisting of a curved square loop with four symmetric semicircular grooves embedded in it, which cracks on metal surfaces. The sensor was modeled and simulated by electromagnetic simulation HFSS software to simulate cracks at different locations and orientations (including $0^{\circ}, 45^{\circ}, 90^{\circ}$, and 135°) on the metal plate. Comparing the radar scattering cross section (RCS) values without and with cracks, it is found that the amplitude-frequency characteristics of the RCS in the presence of cracks show obvious changes, such as amplitude or frequency shifts, to realize effective monitoring of cracks on metal surfaces. The sensor has the advantages of low cost, simple structure, and ease of use.