Frequency-temperature effects in three-dimensional surface acoustic wave periodic structures

Numerical results on the resonant frequencies and their frequency-temperature behavior in a three-dimensional surface acoustic wave (SAW) periodic structure are presented. These results are compared with those of the quartz SAW resonator. The 3D FEM models of SAW periodic structures are useful in the analyses of IDT geometry and crystal cuts of SAW resonators which have power flows transverse to the SAW phase velocity. They are also useful for analyzing transversely coupled SAW resonators. Piezoelectric, Lagrangian equations for the frequency-temperature behavior of quartz are presented. Three-dimensional finite element results for a half wavelength SAW periodic structure are compared with measured data from a SAW resonator. The frequency characteristics of the fundamental SAW mode and its transverse overtones as a function of the electrode length W in the transverse direction are studied. Generally good results are obtained with the 3D FEM models when compared with measured values. Their frequency-temperature behavior are also studied and are reasonably well predicted by the 3D SAW periodic structure. The 2D FEM models are shown to yield results consistent with the 3D FEM models.