Compact Microwave Displacement Sensor

A microwave displacement sensor is reported, which is based on the concept of resonator perturbation. A half-wavelength resonator made of a modified stripline, resonating around 6 GHz, is shorted at both ends. The line’s center capacitance is variably loaded with a metal, or dielectric, sphere mounted on a plunger. The uniaxial displacement of the plunger translates into resonance frequency variation of, in average, about 0.2 MHz/μm. A peak responsivity of 0.3 MHz/μm is observed. The usable displacement range is more than 1.5 mm. The sensor structure is compact, simple and is designed with the aim of low sensitivity regarding potential movement of the plunger in transverse directions.