A Phase Shift-Based and Quadrant-Distinguishable Passive Microstrip Antenna Sensor for Metal Crack Detection

Metal structures play a vital role in modern engineering, underscoring the significance of detecting surface cracks on these structures. This research aims to explore a new approach by employing passive microstrip antenna (PMA) sensors in structural health monitoring (SHM) of metal structures, with particular emphasis on surface crack detection. The presence of cracks on metal structures alters the input impedance and reflected signal phase of the PMA sensor. Consequently, valuable information regarding the location and size of the crack on the metal surface under test can be extracted through these two sensing indicators. This research introduces two points of innovation. First, the use of phase delay and impedance phase angle as detection parameters eliminates the need for wide-range frequency scanning, reducing the complexity and cost of detection compared to traditional methods. Second, the study divides the tested area into four quadrants, initially identifying the crack's region and subsequently extracting various aspects of the crack's information. This approach enables a more comprehensive analysis and precise localization of the crack area and its features. A high-frequency structure simulator (HFSS) simulator is employed to design the sensor model and conduct a series of simulations. The experimental results demonstrate the sensor's remarkable sensitivity in detecting the presence of cracks and accurately differentiating the quadrant position and size parameters of the cracks through phase delay and impedance phase angle. The adoption of PMA sensors offers a relatively simple, accurate, and cost-effective means for SHM of metal structures.