The Propagation Characteristics of Surface Acoustic Waves on Singly and Doubly Rotated Cuts of Quartz

Abstract

The temperature variation of surface acoustic wave (SAW) propagation characteristics on doubly rotated cutsofalphaquartz are discussed. Extensive numerical calculations were used previously to identify families of doubly rotated cuts on which surface acoustic waves exhibit a greater delay time temperature stability than previously reported. Second order temperature coefficients of frequency (TCF) as low as -1.3 x 10-8and zero first order temperature coefficients of frequency were calculated for these families of cuts. In this paper, experimental measurementsof the temperature coefficients of the frequency of selected members of these families of doubly rotated cuts of quartz are presented. Theexperimental measurementsof the temperaturecoefficientsof frequency are compared with the previously calculated values. Phase-temperature plots, coupling coefficients and velocities for these cuts are also presented. In addition, numerical calculations of the temperaturedependence of the surface acoustic wave power flow angle and of the anisotropy parameter Y , which is related to the diffraction effects of the surface acoustic wave, are presented. Power flow variations of 3 degrees and variations of the anisotropy parameter Y of 10 percent (5 percent for the ST-cut) over the temperature range -50°C to 150°C are typical. Experimental measurements of the temperature variation of the surface acoustic wave power flow angle (PFA) are shown to be in close agreement with the calculated variation. The effect of the temperature dependence of the power flow angle and the anisotropy parameter Y on surface wave filters, reflective array devices, and delay lines are discussed both for doubly rotated and the more popular singly rotated Orientations. Techniques for utilizing the temperature dependence of the surface acoustic wave power flow angle to produce temperature stable delay lines are presented. Choice of optimum doubly rotated cuts of quartz for this purpose is discussed, and experimental results are presented.