A 5G n77 Filter Using Shear Bulk Mode Resonator With Crystalline X-cut Lithium Niobate Films

This paper presents the use of a shear bulk acoustic mode resonator made of a membrane of X-cut lithium niobate (LiNbO3) for ultra-wide band filter applications. Aluminum interdigitated (IDT) electrodes are deposited on top of the LiNbO3 thin film as well as a floating electrode made of aluminum deposited on the backside of the membrane. Through vertical field excitation, shear waves are excited with very good performances. The resonator displays more than 40% of electromechanical coupling at 3.3 GHz and 4.2 GHz. We used simulation and characterization results to synthesize and simulate filters and show the potential of this resonator for wideband filtering applications like the n77 band.