P2M-4 Optimization of STW Resonator by Using FEM/BEM

STW (surface transverse wave) resonators on quartz have been widely used in temperature stable oscillator as frequency source applications. In this paper, we use the software FEMSAW based on the FEM/BEM theory to study STW resonator. To simulate the STW resonator with enough accuracy, the FEM/BEM is modified by introducing two parameters to include the propagation attenuation due to material itself in substrate and the loss in Al electrode. By numerical experiment, we found that for the synchronous resonator there exists an optimum thickness of Al electrode, and the optimum thickness depends on center frequency of resonator. We also found that there is an optimum ratio of pitches of reflector and IDT, at which maximum Q-factor can be achieved