Ultra-Large-Coupling and Spurious-Free SH₀ Plate Acoustic Wave Resonators Based on Thin LiNbO₃

This study lays a foundation for the design of the SH₀ plate acoustic wave (PAW) resonators based on LiNbO₃ plate, and are applicable to the ultra-wideband filters and next-generation tunable filters. The coupling coefficient ( k² ) of SH₀ mode is optimized to as high as 55% and wideband spurious are well controlled by analyzing the propagation characteristics of plate modes in LiNbO₃. The SH₀ mode is demonstrated to be slowly dispersive and features the superiority of interdigital transducer (IDT)-defining frequency over most other plate modes. On the device level, the transducer types and electrode materials are investigated and compared. In addition, for edge-reflected SH₀ resonators, stopband dispersion analysis is provided and the longitudinal ripples are suppressed. For edge-reflected SH₀ resonators, a novel perfect edge reflector is proposed with elimination of longitudinal spurious ripples.