Zhao Zinan, Pang Xiangnan, Qian Zhenghua, Kuznetsova Iren, Ma Tingfeng, Yong Yook-Kong
IEEE Trans Ultrason Ferroelectr Freq Control. 2020 Aug;67(8):1647-1655. doi: 10.1109/TUFFC.2020.2981645. Epub 2020 Mar 18.
Mode-coupled vibrations in an ultra-high frequency (UHF) ZnO thin film bulk acoustic resonator (FBAR) operating at thickness-extensional (TE) mode are studied by employing weak boundary conditions (WBCs), constructed based on Saint-Venant's principle and mixed variational principle in the piezoelectric theory. The frequency spectra, describing the lateral size-dependence of mode couplings between the main mode (TE) and undesirable eigen-modes, for clamped lateral edges are compared with the existing frequency spectra for free lateral edges to illustrate the boundary influence. The displacement and stress variations in FBAR volume are also presented to intuitionally understand and distinguish the difference of frequency spectra between these two different lateral edges, and then we discuss how to select outstanding lateral sizes to weaken the mounting effect. The frequency spectra predicted from our approximate WBCs are also compared with and agree well with those predicted by the finite element method (FEM) using COMSOL, which proves the correctness and accuracy of our theoretical method. These results indicate that the WBCs could have potentials in the valid predictions of lateral size-dependence of mode couplings in piezoelectric acoustic wave devices.
通过采用基于圣维南原理和压电理论中的混合变分原理构建的弱边界条件（WBCs），研究了在厚度伸缩（TE）模式下工作的超高频（UHF）ZnO薄膜体声波谐振器（FBAR）中的模式耦合振动。将描述夹紧侧边时主模式（TE）与不良本征模式之间模式耦合的横向尺寸依赖性的频谱，与自由侧边的现有频谱进行比较，以说明边界影响。还给出了FBAR体积中的位移和应力变化，以便直观地理解和区分这两种不同侧边频谱的差异，然后我们讨论如何选择合适的横向尺寸以减弱安装效应。由我们的近似WBCs预测的频谱也与使用COMSOL的有限元方法（FEM）预测的频谱进行了比较，并且两者吻合良好，这证明了我们理论方法的正确性和准确性。这些结果表明，WBCs在有效预测压电声波器件中模式耦合的横向尺寸依赖性方面具有潜力。
