Devices having a tunable acoustic path length and methods for making same

Abstract

A tunable acoustic resonator device. The device has a piezoelectric medium as a first thin film layer and a tunable crystal medium as a second thin film layer. The tunable crystal medium has a first acoustic behavior over an operating temperature range under a condition of relatively low applied stress and a second acoustic behavior under a condition of relatively high applied stress. The acoustic behaviors are substantially different. The tunable crystal medium has a highly field-polarizable and lattice-deformable, substantially centrosymmetric structure over an operating temperature range under a condition of relatively low applied stress. The tunable crystal medium has a substantially non-centrosymmetric structure over said operating temperature range under a condition of relatively high applied stress. The dielectric permittivity of the tunable crystal medium is at least 100 at the relatively low applied stress. The tunable crystal medium is close to its ferroelectric instability but remains paraelectric throughout the operating temperature range of the device. The phase transition temperature of the tunable crystal medium from paraelectric to ferroelectric state is just below the operating temperature range.

Dependencies are inferred from the claim text.