Spectrum-Clean S-1 Aln Lamb Wave Resonator With Damped Edge Reflectors

A concept for the development of spectrum-clean S-1 Lamb wave resonator (LWR) utilizing an aluminum nitride (AlN) plate with damped edge reflectors is demonstrated. Numerical analysis is performed on the dispersive characteristics of the Lamb modes propagating in AlN plates, and the design parameters to enable zero group velocity (v(g)) for the S-1 mode are identified. The simulation results based on finite element analysis verify that the use of the damped edge reflectors, instead of the conventional edge reflectors, can efficiently de-couple most of the Lamb waves such as the S-0 mode by mode conversion upon edges, but not the S-1 mode characterizing zero v(g). Specifically, the measured frequency response of a 1.38-GHz AlN S-1 LWR with damped edge reflectors yields a clean spectrum up to 6 GHz and excellent resonance passband performance.