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

Area of Science:

• Materials Science
• Acoustic Devices
• Filter Technology

Background:

• Lithium Niobate (LiNbO3) is a key material for piezoelectric devices.
• Plate Acoustic Wave (PAW) resonators are crucial for advanced filtering applications.
• Optimizing SH0 mode propagation is essential for high-performance resonators.

Purpose of the Study:

• To establish a design foundation for SH0 mode PAW resonators using LiNbO3.
• To enhance resonator performance for ultra-wideband and tunable filters.
• To investigate and mitigate spurious signal generation in these resonators.

Main Methods:

• Analysis of SH0 mode propagation characteristics in LiNbO3 plates.
• Optimization of the coupling coefficient (k2) for SH0 mode.
• Investigation of transducer types and electrode materials.
• Stopband dispersion analysis for edge-reflected resonators.

Main Results:

• Achieved an optimized coupling coefficient (k2) as high as 55%.
• Successfully controlled wideband spurious signals.
• Demonstrated the slow dispersion and IDT-defining frequency superiority of the SH0 mode.
• Proposed a novel perfect edge reflector to eliminate longitudinal spurious ripples.

Conclusions:

• The SH0 mode in LiNbO3 PAW resonators is highly suitable for ultra-wideband and tunable filters.
• Optimized design and novel reflectors significantly improve resonator performance by suppressing spurious signals.
• This work provides a foundation for next-generation acoustic wave filter design.