2.5 GHz Low-Loss and Wideband Surface Acoustic Wave Filter Based on AL/128°YX-LiNbO3

Abstract

A 128°YX-LiNbO₃-based low-insertion-loss and high-frequency surface acoustic wave (SAW) filter was proposed using COMSOL Multiphysics. The spurious response was suppressed by changing the electrode thickness, reflector period, and reflector structure, after optimization. First, the thickness of the electrode was increased to concentrate the SAW energy on the surface of the piezoelectric material to reduce the propagation loss. Next, an interdigital transducer (IDT) reflector was designed to reduce the insertion loss caused by the spurious response and combined with the optimization of the reflector period. Finally, using this reflector structure when the thickness of the electrode was 0.4 μm, a SAW filter with a center frequency of 2520.5 MHz was designed. The results of the finite element method (FEM) revealed that the insertion loss at the center frequency was –0.1356 dB, the out-band suppression was greater than 30 dB, and the –3 dB bandwidth was greater than 97 MHz.