Resonance Spectrum Characteristics of Effective Electromechanical Coupling Coefficient of High-Overtone Bulk Acoustic
Jian Li1,2, Mengwei Liu3, Chenghao Wang4
1Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China. lijian212@mails.ucas.ac.cn.
Abstract:
A high-overtone bulk acoustic resonator (HBAR) consisting of a piezoelectric film with two electrodes on a substrate exhibits a high quality factor (Q) and multi-mode resonance spectrum. By analyzing the influences of each layer's material and structure (thickness) parameters on the effective electromechanical coupling coefficient (Keff²), the resonance spectrum characteristics of Keff² have been investigated systematically, and the optimal design of HBAR has been provided. Besides, a device, corresponding to one of the theoretical cases studied, is fabricated and evaluated. The experimental results are basically consistent with the theoretical results. Finally, the effects of Keff² on the function of the crystal oscillators constructed with HBARs are proposed. The crystal oscillators can operate in more modes and have a larger frequency hopping bandwidth by using the HBARs with a larger Keff²·Q.
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