Behaviors of higher-order modes in I.H.P. SAW devices and discussion of their suppression

Abstract

In this work, behaviors of higher-order modes in an I.H.P. SAW device with a layered LiTaO3/SiO2/SiN/Si substrate are investigated, and techniques for their suppression are discussed. First, variation of the higher-order mode responses with structural parameters are analyzed using two-dimensional FEM. Then, on the basis of the calculated data, structural parameters are determined for higher-order modes suppression while retaining the main mode characteristics. In addition, the effectiveness of the optimized structure is confirmed using measured data from a fabricated one-port resonator and filters. In the measured data, it is shown that higher-order modes in a specific frequency range are successfully suppressed, while the main made characteristics, such as Bode-Q, bandwidth, and TCF, are almost equivalent to those of conventional I.H.P. SAW resonators and filters.