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 20μ -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 S11 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.