  This work reports the procedure for modeling piezoelectric acoustic
resonators and filters at millimeter wave (mmWave). Different from conventional
methods for lower frequency piezoelectric devices, we include both acoustic and
electromagnetic (EM) effects, e.g., self-inductance, in both the circuit-level
fitting and finite element analysis, toward higher accuracy at higher
frequencies. To validate the method, thin-film lithium niobate (LiNbO3)
first-order antisymmetric (A1) mode devices are used as the testbed, achieving
great agreement for both the standalone resonators and a fifth-order ladder
filter. Upon further development, the reported acoustic and EM co-modeling
could guide the future design of compact piezoelectric devices at mmWave and
beyond.
