A Fin-Mounted A5-Mode Lithium Niobate Resonator at 27.58 GHz with k2 of 4.4%, Q of 448, and FoM of 19.7

This work presents a fin-mounted A5-mode Lamb wave acoustic resonator based on Y128°-cut thin film lithium niobite for millimeter wave frequencies. By using a new fin-mounted structure and optimized electrode geometry, we designed and fabricated a spurious-free A5-mode resonator at 27.58 GHz with k2 of 4.4% and Qp of 448 to achieve a Figure of Merit (FoM) of 19.7, which is the highest in this frequency band. In addition, a ladder-type filter for 3GPP Band n261 with a center frequency of 28.13 GHz based on the fin-mounted resonators was simulated. This demonstration provides a viable solution to the commercial promotion of high-frequency lithium niobate acoustic resonators in the 5G FR2 frequency band.