Transverse Mode Suppression of Thickness Shear Bulk Acoustic Resonators on Lithium Niobate Using Standard and Broadband Piston Mode Designs

This paper describes complete suppression of transverse modes in thickness shear bulk acoustic resonators (TSBARs) using the lithium niobate plate. Previously, the authors conjected from the experiment that cut-off edges with crystal X-plane serve as ideal reflectors for the piston mode operation, and complete suppression is possible by adding the standard piston mode design to the other edges normal to the X-axis. Following to this conjecture, the traditional piston mode structure was designed using two-dimensional finite element method, and the TSBAR was fabricated following to the design. The experiment showed complete suppression of the transverse mode resonances, and the conjecture was verified.