In this paper, we present an approach to studying the mode coupling vibrations in two-port thin-film bulk acoustic wave resonator (FBAR) devices with two pairs of electrodes deposited on the zinc oxide film. The two-dimensional plate theory established in our previous work is employed, which takes into account the coupling of the operating thickness-extensional mode with the extensional, flexural, fundamental and second-order thickness-shear modes. The propagation of straight-crested waves in the plate is studied, and the state-vector approach is successfully used to simplify the derivation process. For a structurally symmetric device, the modes are separated into quasi symmetric and antisymmetric ones. Frequency spectra and corresponding mode shapes are obtained under the stress-free boundary conditions, respectively, and then coupling effects and energy trapping phenomenon are discussed in detail. Some results for structures with asymmetric electrode distributions are also shown. It is found that the choice of aspect ratio has a great effect on mode couplings of FBAR devices. This study will be useful for the design of FBAR filters and sensors.

中文翻译：

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横向声耦合两端口薄膜体声谐振器的二维耦合振动分析

在本文中，我们提出了一种方法，用于研究在氧化锌膜上沉积两对电极的两端口薄膜体声波谐振器（FBAR）器件中的模式耦合振动。我们在先前的工作中建立了二维板理论，该模型考虑了工作厚度-拉伸模式与拉伸，弯曲，基本和二阶厚度-剪切模式的耦合。研究了板波在波板中的传播，并成功地使用状态矢量方法简化了推导过程。对于结构对称的设备，将模式分为准对称模式和反对称模式。分别在无应力边界条件下获得频谱和相应的模式形状，然后详细讨论了耦合效应和能量俘获现象。还显示了具有不对称电极分布的结构的一些结果。发现纵横比的选择对FBAR器件的模式耦合有很大影响。这项研究对于FBAR滤波器和传感器的设计将是有用的。