Modeling of in-plane diffraction in a surface acoustic wave resonator based on coupling-of-mode theory

Abstract This paper discusses modeling of the in-plane diffraction in surface acoustic wave (SAW) resonators. The theory is based on the simple conventional one-dimensional coupling-of-modes theory, and its result is used to estimate power leakage caused by the in-plane SAW diffraction. TC-SAW resonators on the SiO 2 /131°YX-LN structure and I.H.P. SAW resonators on the 42°YX-LT/SiO 2 /Si structure are used for the discussions. First, the parameters required for the analysis are determined by fitting with the simple periodic 2D FEM results. Then, the impact of the in-plane diffraction is estimated by the proposed model. The numerical results can explain the variation of the Bode Q with N I and W obtained by the full 3D FEM well. It is also shown that the Bode Q of the I.H.P. SAW resonators decreases with the frequency much slower than that of the TC SAW resonators. This is due to the difference in the SAW slowness shape in these configurations, and this explains the reason why I.H.P. SAW resonators offer larger anti-resonance Q than TC SAW resonators.