Nonlinear modeling of the temperature coefficient of frequency of microacoustic resonators

Abstract

Surface acoustic wave (SAW) filters play an essential role in radio frequency communications. To meet the demands of narrow guard bands, the temperature coefficient of frequency (TCF) of the filters must be deliberately controlled, which is closely related to the increasingly complex material system and boundary conditions. Consequently, modeling and accurate prediction of TCFs with previous theories has become a significant challenge. This research follows continuum mechanics to analyze the finite deformation in complex SAW resonator structures. Thermoelastic constitutive relations containing high-order nonlinear terms are developed for an accurate solution of the thermally induced finite deformation. A model for precise simulation of resonator TCF is developed, with the material and geometric nonlinearity effects from the finite deformation included in the effective material constants and field equation. Results from the developed model are compared against the experimental results for structures including temperature compensated SAW and wafer bonded SAW, thereby showing the accuracy of the model. Additionally, an improved piezoelectric-on-insulator (POI) based structure for SAW resonators is proposed with its performance comparable to commercialized thin film SAW (TF-SAW) technologies while resonant and anti-resonant TCFs differing lower than 10 ppm/^∘C.