Analysis of frequency-temperature behavior of X-cut LiTaO3 strip resonators

We numerically studied the f-T behavior of the fundamental TS fast mode in a partially plated X-cut LiTaO₃ strip resonator. Using the material constants measured by Smith and Welsh [1971], the f-T curves were calculated as a function of the electrode-length and the plate-length direction ψ. The results confirmed that the turnover temperature of f-T curve decreases with increasing the electrode length. Furthermore we found out that the turnover temperature changes according to the coupling between TS and TF modes through c₅₆, and that it therefore depends on the plate-length direction ψ. An angle ψ=40° that yields the turnover temperature in the range of 33~6.5°C is optimal for the material constants of Smith and Welsh because c₅₆ is zero. We also showed that the external loading of both series and parallel capacitances can make the adjustment of turnover temperature very flexible