Relation Between Electrode Thickness and Optimal Tilted Angle for Suppressing Transverse Modes in TF-SAW Resonators

TF-SAW resonators based on the POI substrate are attracting intensive research due to the outstanding Q factors which are highly important for filters’ insertion loss. However, the presence of transverse modes causes severe pass-band ripples and out-of-band spurs in filter characteristics. Since the cut-off frequency of each transverse mode depends on the aperture of the IDTs and the bus-bar width, their adjustment allows suppression of the transverse modes possible. Tilted IDTs have been reported to suppress the unwanted transverse modes, without deteriorating the Q or adding process complexities. In this work, we investigated the relation between normalized electrode thickness and optimal tilted angle for suppressing transverse modes.