SAW temperature sensor with mirror topology

One of the main directions for improving surface acoustic wave (SAW) sensors is to increase the range of operation. Besides achieving greater interrogation distances, the aim of this work is to increase the amount of information that can be obtained from the sensor. The design of the sensors with mirror topology assumes that there is a significant difference in variation of SAW propagation velocity with temperature in two different substrates. The search for optimum piezoelectric materials showed that it is preferable to use two different cuts of lithium niobate (Y-Z-cut and 128°Y-X-cut). The achieved measurement distance with a 1.8 μs long interrogation pulse and 10 mW average power exceeded 30 m at 433 MHz. Measurement accuracy in the range of −50 to 50 °C was better than ±5°C.