Conceptual Designs of a High Q, 3.4 GHz Thin Film Quartz Resonator

Abstract

Theoretical analyses and designs of high Q, quartz thin film resonators are presented. The resonators operate at an ultra-high frequency (UHF) of 3.4 GHz for application to high frequency timing devices such as cesium chip-scale atomic clocks. The frequency spectra for the 3.4 GHz thin film quartz resonators which serve as a design aid in selecting the resonator dimensions/configurations for the simple electrode, and ring electrode mesa designs are presented here for the first time. The thin film aluminum electrodes are found to play a major role in the resonators because the electrodes are as much as one third the thickness and mass of the active areas of the plate resonator. Hence, in addition to the material properties of quartz, the elastic, viscoelastic and thermal properties of the electrodes are included in the models. The frequency-temperature behavior is obtained for the best resonator designs. In order to improve the frequency-temperature behavior of the resonators, new quartz cuts are proposed to compensate for the thermal stresses caused by the aluminum electrodes and the mounting supports. Frequency response analyses are performed to determine the Q, motional resistance, capacitance ratio, and other figures of merit. The resonators have Q's of about 3800, resistance of about 1300 to 1400 ohms, and capacitance ratios of 1100 to 2800.