发表机构
École Polytechnique Fédérale de Lausanne (EPFL)（洛桑联邦理工学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文提出双层X切铌酸锂厚度剪切体声波谐振器，利用对称性工程抑制杂散模式，在6 GHz实现约35%的k2eff和18.6%分数带宽，适用于下一代宽带射频滤波器。
AI 中文摘要
无线通信标准向更高频率和更宽带宽的演进对声学滤波器技术提出了日益增长的需求。传统谐振器在5 GHz以上面临缩放限制，其中光刻约束、降低的机电耦合系数（k2eff）以及杂散模式激励阻碍了实际滤波器的实现。在此，我们介绍一种双层X切铌酸锂（LiNbO3）厚度剪切体声波谐振器架构，该架构利用对称性工程作为新的设计自由度。通过垂直堆叠两个压电薄膜并采用定制键合角度，可选择性地激励二阶厚度剪切模式（SH2，慢波）。此外，X切LiNbO3固有的快厚度剪切模式被抑制，从而产生无杂散的带内响应。工作在6 GHz附近的器件展示了约35%的k2eff，与有限元模拟结果紧密吻合，证实了对称性驱动的模式选择机制。概念验证的梯形滤波器展示了18.6%的分数带宽，突显了所提出架构的宽带能力。所提出的配置实现了厚度定义的频率缩放，同时保持高耦合和频谱纯度，为下一代无线系统中的宽带射频滤波器提供了一个有前景的平台。
英文摘要
The evolution of wireless communication standards toward higher frequencies and wider bandwidths places increasing demands on acoustic filter technologies. Conventional resonators face scaling limitations above 5 GHz, where lithographic constraints, reduced electromechanical coupling coefficient (k2eff), and spurious mode excitation hinder practical filter implementation. Here, we introduce a bilayer X-cut lithium niobate (LiNbO3) thickness-shear bulk acoustic resonator architecture that leverages symmetry engineering as a new design degree of freedom. By vertically stacking two piezoelectric thin films with a tailored bonding angle, the second-order thickness-shear mode (SH2, slow) is selectively excited. Furthermore, the fast thickness-shear modes inherent to X-cut LiNbO3 are suppressed, yielding a spurious-free in-band response. Devices operating around 6 GHz demonstrate a k2eff of approximately 35%, in close agreement with finite-element simulations and confirming the symmetry-driven mode selection mechanism. Proof-of-concept ladder filters demonstrate a fractional bandwidth of 18.6%, highlighting the wideband capabilities of the proposed architecture. The proposed configuration enables thickness-defined frequency scaling while maintaining high coupling and spectral purity, offering a promising platform for wideband radiofrequency filters in next-generation wireless systems.
Comments17 pages, 4 figures
