Tuning of a Surface Acoustic Wave Resonator Formed of Lithium Tetraborate Substrate Combined with Piezoelectric Ceramic Element

Abstract

Tuning of resonant characteristics, especially of resonant frequency, was studied on surface acoustic wave resonator, which was formed on a lithium tetraborate substrate and adhered to a poled piezoelectric ceramic element. The resonant frequency was tunable when a electric field (up to 1.5 kV/mm) was applied to the piezoelectric element. The magnitude of resonant frequency tunining was about 600 ppm, so that the temperature coefficient of resonant frequency change could be tuned to be constant or almost zero ppm/°C over the experimental temperature range between 0 and 75°C. The mechanism of tuning is considered to be that the distance between interdigital electrodes on the resonator was changed as the piezoelectric ceramic element was actuated and deformed with the application of electric field.