An Angular Displacement Microwave Sensor With 360° Dynamic Range Using Multi-Mode Resonator

This article presents the application of a novel multi-mode resonator (MMR) named rotational cross-shaped resonator (RCSR) to the design of a planar angular displacement microwave sensor. This MMR developed by four connected stubs with short and open terminations. Since the generated transmission zeros of the RCSR vary linearly with changes in stub lengths, the RCSR structure that makes use of this principle is proposed for implementing angular displacement sensing. The sensor consists of an open-ended stub of RCSR housed by a circular rotor and the rest of the RCSR on the stator. As the position of the stub of RCSR is modified by rotating the rotor, the generated transmission zeros will drift accordingly. Based on the multiple zeros, the proposed angular displacement sensor can provide distinctive direction of rotation detection in addition to dual-sensing measures output. A sensor prototype at 1.95 GHz is designed and experimentally characterized, which reports that both the angle and direction of rotation detections can be realized. The average frequency sensitivity in terms of the variation of a single transmission zero is 1.22 MHz/degree for the dynamic range from -180° to 180°, as well as the average bandwidth sensitivity in terms of the frequency difference between two zeros is 2.61 MHz/degree for the dynamic range from 0° to 180°.