BAW Microwave temperature sensor

This work is aimed at the study of a potential possibilities of microwave Bulk Acoustic Wave resonators for temperature measurements. The resonators under study had nonstandard high overtone BAW resonator configuration: a thin piezoelectric film ZnO with electrodes was deposited onto the surface of the substrate made of the (100) oriented YAG plate with the thickness 480... 980 mum. The new technical solution was that resonator was acoustically isolated and protected from the ambient mechanical influence. For this purpose the bottom side of the plate and the top electrode of the resonator structure were isolated from ambient by a nine-layer Bragg Ti-W quarter-wave length thin film reflectors. Due to the isolation it can become no sensitive even to liquids getting on the surfaces of the resonator. Total thickness of all deposited layers was less than 12mum. The resonator aperture was less than 600mum.