A Planar Microwave Angular Displacement Sensor Based on Microstrip Line Loaded Split Ring Resonators

In this paper, a planar microwave angular displacement sensor based on microstrip line loaded split ring resonators (SRRs) is designed. The main body of the sensor is a stator formed by two overlapping layers of FR-4 substrates, consisting of a primary SRR (PSRR) coupled with a $\Omega$-shaped microstrip on the lower layer substrate, and a circular window opened on the upper layer substrate to fix a rotor. The rotor is a rotatable SRR (RSRR) designed on a circular substrate, capable of being embedded in the circular window of the stator to couple with the PSRR. Simulation results show that the operating frequency range of the sensor is from 0.95 GHz to 1.75 GHz, and the sensor can achieve a dynamic detection range from 0° to 180° with an absolute sensitivity of 1.44 MHz/°. After analyzing rotor positioning error, it has been confirmed that the sensor's detection ambiguity is limited to within a 5-degree range, indicating promising potential for diverse applications in various industries.