Design of a High-Sensitive Chipless RFID Sensor for Surface Crack Characterization on Metals

This paper presents the design of a high-sensitivity chipless RFID sensor tag with a modified depolarizing circular patch for surface crack characterization on metals. The sensor response was realized using a cross-polarization reading, and induced dual resonance frequencies from the incident waves. The circular patch resonates at frequencies of 2.766 GHz and 3.204 GHz with four L-shaped tip-loaded resonators as identification encoders. The surface cracks in vertical, horizontal, and diagonal orientations with varying crack widths and depths in sub-millimeter resolution are simulated. It is observed that the designed patch is sensitive to detect a minimum crack resolution of 0.1 mm for varying crack widths and depths. The average computed gradient of simulated sensor upper frequencies is 27.5 MHz and 58.5 MHz for varying crack depths and widths in vertical orientation. Similarly, varying frequency gradients between dual resonances were observed for other orientations.