WIRELESS SAW-BASED TAGS WITH TEMPERATURE SENSORS THAT UTILIZE HIGH-RESOLUTION DELAY-TIME MEASUREMENTS

Surface acoustic wave (SAW) devices are widely used in commercial products as filters and resonators. SAW devices are also applied as passive, wireless radio frequency identification (RFID) tags and sensors, which can be used in harsh environments and consume no batteries. In this study, we designed and fabricated an SAW-based RFID tag with the added function of a high-resolution temperature sensor. A coupling of modes model was adopted to design 433MHz SAW-based tags/sensors. An improved signal processing method was used to increase the resolution of time-domain signals, enabling the slight change of delay time caused by temperature variation to be detected. Subsequently, the SAW tags/sensors were fabricated on 128. Y-cut lithium niobate and used to detect temperature shifts. The results revealed that high-resolution delay-time SAW devices are feasible for measuring temperatures precisely and can be applied to other SAW-based sensors.