Investigation of Lithium Niobate (LN) and Lithium Tantalate (LT) for ultra-high frequency (UHF) monolithic BAW filter applications

A theoretical study has been carried out for a 1.0 3.0 GHz rectangular monolithic BAW filter configuration for different Y-cut angles of LN and LT using 3-D finite element (FEM) models. The frequency-temperature characteristics for cut angles varying from 0 deg to 180 deg for Y-cut LN and Y cut LT is evaluated using 3-D FE analysis. The performance of the monolithic filters as a function of resonator geometry, and acoustic gap is studied. FEM results for different Y-cut angles of LT and LN are obtained with respect to the optimal resonator geometry. FEM results show that Y-cut LN has a higher band-width as compared to that of the Y-cut LT, however LT shows a better TCF and a lower loss as compared to that of LN. Based on the 3D-FEM analysis cut angle in the range of 170 to 178 deg for Y-cut LN and 158 to 165 deg for Y cut LT are identified as the promising cut angles for possible UHF applications.