摘要
This work investigates the design trade-offs associated with implementing ultra-wide fractional-bandwidth (FBW) RF filters on a thin-film lithium-niobate-on-insulator (LNOI) platform. By appropriately selecting the wavelength ratio between the series and shunt resonators in a ladder topology, an ultra-wide FBW approaching 40% can be achieved using shear-horizontal surface acoustic wave (SH-SAW) resonators with a large electromechanical coupling coefficient (keff2). The fabricated 2-stage ladder filter achieves a maximum FBW of 37.4% with an insertion loss (IL) of 1.5 dB at 1.2 GHz, in good agreement with the predicted performance. A numerically synthesized 3.5-stage ladder filter further demonstrates an FBW of 36% at 1.2 GHz with sub- 3 dB IL and 25 dB out-of-band rejection, underscoring the promise of acoustic-wave technology for wideband RF filter design. © 2026 IEEE.