Displacement Sensor With High Sensitivity and Linearity Based on a Half-Wavelength SIR for Crack Width Measurement

In this work, a displacement sensor designed for measuring crack width is proposed. The sensor is based on a half-wavelength stepped impedance resonator (SIR) consisting of a fixed transmission line and a movable patch. The sensor was analyzed using a full-wave simulator (HFSS) and experimentally measured using a vector network analyzer (VNA). The sensor’s experimental sensitivity is 0.121 GHz/mm, with linearity, assessed by the coefficient of determination, of 0.998. Both sensitivity and linearity were measured within a measurement range from 0 to 8.5 mm, with an initial resonance frequency of 2.701 GHz. Additionally, the sensor’s resolution is 0.06 mm. The proposed sensor demonstrates high sensitivity and linearity, along with low distortion within the test measurement range.