A Dual Resonance Frequency-Selective Surface Temperature Sensor With Linear Frequency–Temperature Behavior

Metamaterial temperature sensors are receiving increasing attention due to the wireless and passive operation. Unfortunately, the frequency response of most metamaterial sensors to temperature is nonlinear, which increases the complexity of signal processing. A dual resonance frequency-selective surface (FSS) temperature sensor with linear frequency–temperature characteristic is proposed in this work. The dual-frequency resonance of the sensor is realized by introducing the circular slot unit cell into the substrate integrated waveguide (SIW) structure. The linear relationship between the temperature and the difference in the two resonance frequencies can be achieved at specific conditions. The proposed sensor was fabricated and measured from room temperature to 120 °C. The measured resonance frequency of the sensor decreases from 12.658 to 12.57 GHz in the SIW cavity resonance mode and from 13.787 to 13.727 GHz in a circular slot resonance mode. The experiment result shows that wireless temperature sensing is feasible and that the difference in resonance frequency has a good linear relationship with temperature. The sensitivity of the sensor is 0.309 MHz/°C. This design method can be extended to a wider temperature range and the sensor can be potentially applied to temperature sensing in industrial systems.