A Wireless Metamaterial-Inspired Passive Rotation Sensor With Submilliradian Resolution

A novel passive wireless rotation sensing system with high levels of sensitivity and resolution is proposed and demonstrated for measuring elastic-region bending in materials such as steel. This system is composed of a transceiver antenna and a double-plate sensor in the form of an inter-digital configuration, which does not incorporate any active component. The sensor exhibits a large rotation resolution of <inline-formula> <tex-math notation="LaTeX">$20~\mu $ </tex-math></inline-formula>-rad, an excellent sensitivity of 28 MHz/° in average, and a large linear dynamic range of approximately 40°. In operation, as a result of the relative rotation between the plates of the sensor, the operating resonance frequency of the system is shifted. This is read out and tracked in the <inline-formula> <tex-math notation="LaTeX">$S_{11}$ </tex-math></inline-formula> response of the transceiver antenna from which the rotation angle is determined. The prototype is designed for microwave regime and it is suitable for measuring very small angles (10⁻⁴ ~ 10⁻⁵ rad). Critical figures-of-merit of the sensor including sensitivity, dynamic range, and resolution are assessed via systematic measurements, and the validity of resolution experiment is verified by employing digital image correlation method for 2-D measurements.