This paper proposes a displacement sensor using a cylindrical dielectric resonator (DR) coupled to a pair of parallel, open- ended microstrip lines. This circuit enables displacement sensing through the measurement of the transmission coefficient (S-21-parameter) between the microstrip lines. The sensor operates at a fixed frequency of similar to 3.7 GHz, which is the resonant frequency of the DR, excited in the TE011+delta mode, by the coupling circuit. The displacement of the DR relative to the open ends of the microstrip lines changes the coupling coefficient (k) between the DR and the lines, resulting a change in the measured S-21-parameter. In simulations, the variation of k with displacement is found to be nearly linear in the range of 1-10 mm. To demonstrate the sensor operation, a laboratory prototype of the sensor is fabricated and experimentally characterized using two different setups. The first setup uses a standard vector network analyzer (VNA), while the second setup has a less costly system comprising a signal generator and a power meter. Sensitivity plots (k vs displacement) generated from both the methods show good agreement with the simulated plot, demonstrating a linear range of 2-8 mm.
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