High temperature packaging for surface acoustic wave transducers acting as passive wireless sensors

Numerous developments have been dedicated these passed years to demonstrate the use of surface acoustic wave (SAW) devices as passive sensors probed through a wireless radio-frequency link. Giving access to physical parameter variations without embedded power supply, recent works have shown that SAW sensors can be used under harsh environments such as temperatures in excess of 300 °C and much more. The purpose of this paper is to present a new packaging process for SAW sensors operating under temperature environments up to 600 °C. The robustness of this packaging process is first validated at the above-mentioned temperature using a classical temperature probe via wired connection. The reliability of this process applied to differential SAW sensors then is demonstrated by wireless interrogation of a quartz-based SAW differential sensor from room temperature to 480 °C. The sensor operation has been validated for several tens of hours without major failure nor significant deviation, although the measurement distance dynamic range is observed to be dramatically reduced with operating on such a wide temperature range.