Optimal design for an innovative very-high-temperature hybrid SAW sensor

Surface Acoustic Wave sensors are a promising enabling technology to achieve temperature monitoring in extreme conditions, and especially at very high temperature, above 900°C. Applications in the air and space, chemical, steel, and automotive industries are notably expected. Although many of the technical challenges posed by the development of these sensors have been tackled and solved over the years, there is still no SAW sensor able to withstand very high temperatures for a long time on the market (yet). A possible alternative could be to combine a SAW transponder with a thermocouple ('SAW Hybrid'). The thermocouple would be read wirelessly using a SAW transponder, itself located at a place nearby where the temperature doesn't exceed 350°C. The feasibility of this concept was recently demonstrated, using a 400MHz device. However, the obtained sensitivity was very low, and an optimized Design is needed, to increase it. It is notably expected that a higher operating frequency will significantly improve the sensitivity. In this paper, we present an optimal Design of the SAW Hybrid AlN/LN multilayered structure, for operation at 2.45GHz, with buried Pt electrodes.