Numerical analysis and design of a high-frequency surface acoustic wave transducer: influence of piezoelectric substrates and IDTs configurations

Abstract

The development of SAW transducers requires a series of steps ranging from material selection, geometry design, as well as, the selection of fabrication techniques for their characterization and validation process. Here, we use the finite element method in COMSOL Multiphysics to present a methodology and a detailed analysis of the design of a SAW transducer in a delay line configuration. First, we simulate single-finger and double-finger configurations of IDTs on LiNbO3 in 64°YX and LiNbO3 128°YX orientation, with the objective of 1) comparing the simulation results with the analytical delta model to validate the simulation process, presenting Pearson correlation values ranging from 0. 76 to 0.84. 2) calculate a maximum frequency value obtainable for those configurations from a resolution of 5 microns in the photolithography technique, used for the fabrication of SAW transducers. Next, we extended the analysis to study a specific transducer design made to operate at a resonant frequency of 97 MHz. In order to determine the influence of piezoelectric material and IDT configuration we compared identical designs on 128°YX and 64°YX orientations of LiNbO3 with single and double finger configurations and adding the SPUDT configuration. We observed the best results for the single-finger IDT configuration in 128°YX LiNbO3 orientation compared to the other variants through its insertion loss level of -7.29 dB, its average sidelobe level of 18.63 dB, and its average transition band slope for the main lobe of 119.59 dB/MHz. The results obtained can serve as a guide for new researchers or students to expand the use of numerical tools in the design of SAW transducers and SAW devices.