  This work presents a new class of micro-electro-mechanical system (MEMS)
resonators toward Ka band (26.5-40GHz) for fifth-generation (5G) wireless
communication. Resonant frequencies of 21.4 and 29.9 GHz have been achieved
using the fifth and seventh order asymmetric (A5 and A7) Lamb-wave modes in a
suspended Z-cut lithium niobate (LiNbO3) thin film. The fabricated device has
demonstrated an electromechanical coupling (kt2) of 1.5% and 0.94% and
extracted mechanical Qs of 406 and 474 for A5 and A7 respectively. The quality
factors are the highest reported for piezoelectric MEMS resonators operating at
this frequency range. The demonstrated performance has shown the strong
potential of LiNbO3 asymmetric mode devices to meet the front-end filtering
requirements of 5G.
