Acoustic Surface Wave Resonators and Filters on ST Quartz

摘要

The objective of this program is to maximize the usefulness of surface acoustic wave (SAW) resonators for applications to filter and oscillator circuits. This program focuses on improving fabrication to yield the lowest possible aging rate, designing a 70-MHz resonator to achieve the highest possible Q, and examining the use of resonators at higher frequencies with a 600-MHz filter. The program was divided into three sections: aging studies, high-Q studies, and a high-frequency study. In the area of aging, the results of a previous study with the Office of Naval Research were used to determine the optimum fabrication and mounting procedure for SAW resonators. The goal of this work was to determine the aging rate for resonators made in this manner and to determine the effect of elevated temperatures on this rate. This data would then be used to determine the best preaging cycle to obtain long term stable operation. In addition, the effects of tuning with ZnO and of an arbitrary preaging cycle were measured. In the high-Q studies, the sources of loss in the resonator were analyzed and an approach was identified to achieve the contract goals. The devices built under this contract do not meet the contract goals, but the sources of additional loss have been identified. The devices built under this section have been made into one-pole filters. The high-Q results show that the loss mechanisms in grooved quartz resonators are well understood, but further effort is needed in the area of reflector weighting for bulk scattering suppression and for improved filter out-of-band rejection. The filters built under this study exhibited a maximum Q of 40,000 in vacuum.