In this research, a wireless and passive relative displacement sensor structure is designed based on a backscatter communication system, providing a flexible and cost-efficient option for Structure Health Monitoring (SHM) application. The proposed sensor arranges a pair of Copper-Clad Laminates (CCL) in parallel with adjustable distance as a RF resonator. To wirelessly detect the frequency characteristic of proposed RF resonator, a backscatter communication system is employed, and the system transmission loss (S21) is measured. According to the results from both simulation and experiments, a consistent relationship is established between S21 peak frequency shifting and the distance between paralleled laminates. In relative displacement experiments, a resolution of under 0.01 mm within a 0.6 mm sensing range is achieved. Compared to the previous research, the proposed sensor structure enables vertical relative displacement sensing between paralleled laminates, which increases the flexibility in sensor deployment within confined structures.
