Suppression of Transverse Mode Responses in Ultra-Wideband SAW Resonators Fabricated on a Cu-Grating/15°YX-LiNbO₃ Structure

Abstract

This paper discusses a technique to suppress spurious transverse mode responses appearing in ultra-wideband SAW resonators fabricated on a Cu-grating/15 degrees YX-LiNbO3 structure. The basic idea of the technique is inserting length- and width-weighted dummy electrodes between a bus-bar and interdigital electrodes. For practical device design, an analysis was made to show how the profile (field distribution) of both dominant and spurious transverse modes depends on the length and width (equivalent to SAW velocity) of the dummy electrodes. IDT-type SAW resonators were fabricated on a Cu-grating/15 degrees YX-LiNbO3 structure using the length- and width-weighted dummy electrodes. The experimental results were in good agreement with the theoretical analysis and prediction, showing that the proposed technique is effective in suppressing the spurious responses caused by the transverse modes.