A Thin-Film CdS-Quartz Composite Resonator

Abstract

A new type of miniature resonator for the 100–1000‐MHz range has been developed which consists of a piezoelectric CdS transducer evaporated onto a single‐crystal quartz wafer. Energy trapping principles have been applied to localize the acoustic energy in the quartz wafer to the volume under and immediately surrounding the electrically driven CdS film. Resistances at resonance of 50 Ω and electrical Q's of 5000 typically have been realized with 279‐MHz devices. Both shear and longitudinal mode resonators have been fabricated, but shear mode operation has the important advantage that devices with a zero frequency‐temperature coefficient are possible.