Serially connected strip-type acoustic wave resonator using X-40°Y LiNbO₃ (XSAR)—feasibility study using macro model

Abstract

This work presents a new serially connected strip-type acoustic resonator using X40°Y-LiNbO3 (LN) (XSAR). The proposed design is composed of a serial of strip-type bulk acoustic wave (BAW) resonators connected together. The volume between two strips is penetrated through to eliminate the spurious response and enhance quality (Q) factor. The Euler angle (90°, 90°, 40°) of LN is optimized to obtain the maximal piezoelectric constant e34, which determines the coupling factor of shear mode of the resonator. Simulation results show that the new design is superior in terms of impedance ratio (Z-ratio) and bandwidth (BW) and exhibits the largest BW of 32% ever reported. The slow shear mode spurious response is successfully removed by the proposed penetrated structure combined with narrow strip. Furthermore, the device was prototyped in macro scale using 350 μm thick LN, by which the ultra-wide BW and potentially good performance in high frequency were confirmed.