Crack Detection in Metallic Surfaces Based on Dumbbell-Shaped Defected Ground Structures in Microstrip Technology

In this paper, a novel crack detection sensor using a microstrip loaded with a Dumbbell-Shaped Defected Ground Structure (DS-DGS) is proposed. The sensing element is etched in the ground plane of a microstrip line and it is easy to fabricate. The electromagnetic (EM) field of the microstrip couples to the DS-DGS, thus demonstrating a bandstop behavior. It is shown that in the presence of a crack in a metallic surface underneath the sensor, the resonance frequency of the DS-DGS is shifted. This frequency shift can be used for crack sensing in metallic surfaces. The proposed sensor exhibits a good sensitivity above 260 MHz shift for a crack with a 200 μm width at the relatively low operating frequency of around 2 GHz.