A miniaturized and high Q-factor wireless passive frequency selective surface temperature sensor based on stacking coupling structure

Metamaterial temperature sensors are gaining increasing attention due to their wireless passive operation. Most metamaterial temperature sensors are single-layer resonance structure, which are limited in terms of miniaturization and high quality factor (Q factor). In order to alleviate these issues, a frequency selective surface (FSS) temperature sensor based on stacking coupled inductive and capacitive layers is proposed in this work. By stacking metal layers in three dimensions, the equivalent inductance or capacitance can be adjusted independently at each layer. In addition, the equivalent capacitance has significantly increased with the proposed new wide strip and interdigital patch structures. The size of the FSS unit cell is as compact as 0.09λ0. The measured results show that the Q-factor of the FSS sensor is about 1383 at 16.797 GHz and the resonance frequency of the FSS sensor decreases from 16.732 GHz to 15.609 GHz when temperatures increase from 25°C to 900°C. The average sensitivity of the sensor is 1.29 MHz/°C. Being wireless, passive and miniaturized, the proposed high-temperature sensor can be used for various industrial systems.