A High-Linearity Planar Angular Displacement Sensor Based on Dual-Mode Tapered RingResonator

A microwave angular displacement sensor with a 120° dynamic range (DR) and high linearity is designed and fabricated. The sensor employs a dual-mode tapered ring resonator (TRR) as the stator, integrated with a rotatable rotor. The sensor implements real-time rotation angle measurement by simultaneously monitoring both the resonance frequency difference and the resonance depth variation to resolve the ambiguity caused by the non-monotonic response. Measurement results demonstrate two distinct operational regimes: 1) for rotation angles between 0° and30°, the resonant frequencies converge, causing their difference to decrease from 1.9 to 1.23 GHz; and 2) for rotation angles between 30° and 120°, the resonant frequencies diverge, resulting in an increase in the frequency difference from 1.23 to 2.03 GHz. The sensor exhibits excellent linearity ( $\le 4.68$ % full scale) within the 120° measurement range and achieves a high sensitivity of 22.33 MHz/° within the 0°–30° range and 8.89MHz/° within the 30°–120° range.