5 GHz Acoustic Delay Lines using Antisymmetric Mode in Lithium Niobate Thin Film

This paper demonstrates the first group of acoustic delay lines (ADLs) at 5 GHz, using the first-order antisymmetric (A1) mode in Z-cut lithium niobate thin films. Thanks to the fast phase velocity, large coupling coefficient, and low-loss of A1 waves, the implemented ADLs significantly surpass the operation frequency of precious works with similar feature sizes. The impact of the key design parameters on the device performance is first discussed. The implemented ADLs at 5 GHz show a minimum insertion loss of 7.9 dB, and delays ranging between 15 ns and 109 ns over a fractional bandwidth around 4%. The propagation characteristics of A1 mode acoustic waves have also been extracted for the first time. The A1 ADLs can potentially enable wideband high-frequency passive signal processing functions for future 5G applications in the sub-6 GHz spectrum bands.