Wireless interrogation of antenna sensor to detect hidden cracks

Abstract

Recently, we have validated that microstrip antenna can detect sub-millimeter crack growth. The wireless interrogation of the antenna sensor under line-of-sight illumination of an interrogation antenna has also been demonstrated. In this paper, we present a wireless interrogation technique that is out of the line-of-sight of the interrogation antenna. This technique enables detecting and monitoring crack propagation between a lap joint or in any other case where a crack is hidden between two parts of a structure. Implementation of the sensor and the wireless interrogation unit using commercially available microwave components is presented in detail. The experimental results confirmed the capability of this technique to wirelessly interrogate the antenna sensor. In addition to crack propagation detection, this technique can also be used to monitor compressive forces between two faying surfaces of a lap joint structure.

Passive wireless strain and crack sensing using a RFID-based patch antenna

“…When the patch antenna is deformed by tension F, which induces strain ε, the antenna frequency shifts to [17]: With simple mathematic manipulations, the relationship between the strain ε and the frequency shift can be written as:…”

Method of Monitoring Cracks in a Metal Structure Based on Dual-Chip RFID Antenna Sensor

“…Therefore, it is critical to eliminate the interference of the surrounding clutter signal. Yi, Huang and Yao et al proposed the wireless testing method based on the frequency doubling principle [7], the switching circuit [8], the double horn antenna [9], the impedance switch circuit controlled by an oscillator [10] and the delay function of the microstrip line [11], respectively. However, all the antenna sensors above are externally connected to the modulation circuit, and the sensor structure and test system are relatively complex.…”