A Fixed-Frequency Angular Displacement Sensor Based on Dielectric-Loaded Metal Strip Resonator

A fixed-frequency angular displacement sensor using a dielectric-loaded metal strip resonator is proposed. The dielectric body on which the strip resonator is attached is a cylinder having a high dielectric constant ( \varepsilon _{\mathbf {r}} \gg ~1 ). The resulting resonator operates at the half-wave resonant frequency of the quasi-TEM mode of the loaded strip, which is much lower than the nominal resonant frequency of the strip. To enable angle sensing, the resonator is placed symmetrically between two 50~\Omega , open-ended microstrip lines, so that the magnitude of the transmission coefficient ( \vert \text{S}_{\mathbf {21}} \vert ) between the lines varies with the strip angle, i.e., 0^{\mathbf {0}} \le \theta \le 90^{\mathbf {0}} . Also, this configuration ensures constant resonant frequency operation for all angles. Simulations show that although the \vert \text{S}_{\mathbf {21}} \vert versus angle curve varies exponentially in the range of 0^{\mathbf {0}} \le \theta \le 90^{\mathbf {0}} , the corresponding coupling coefficient varies quasi-linearly in 10^{\mathbf {0}} \le \theta \le 80^{\mathbf {0}} . A laboratory prototype for ~ 2.4 GHz resonant peak is fabricated and the simulation results are verified through prototype measurement. The advantages of the proposed sensor are that it is compact, has a simple design, and operates at a fixed frequency, enabling a low-cost, robust angular sensor.