Patent ID: 7362198

Claim:
A decoupled stacked bulk acoustic resonator (DSBAR) device, comprising: a lower film bulk acoustic resonator (FBAR) and an upper FBAR stacked on the lower FBAR, each FBAR comprising opposed planar electrodes and a piezoelectric element between the electrodes; and an acoustic decoupler between the FBARs, the acoustic decoupler comprising a first acoustic decoupling layer of a first acoustic decoupling material and a second acoustic decoupling layer of a second acoustic decoupling material, the first acoustic decoupling material having an acoustic impedance different from the second acoustic decoupling material, wherein one of the first acoustic decoupling material and the second acoustic decoupling material have an acoustic impedance of about 2 Mrayl, in which the DSBAR device is characterized by a center frequency and the acoustic impedances and thicknesses of the acoustic decoupling layers are chosen to cause the acoustic decoupler to impose a nominal phase change of an odd integral multiple of π/2 on an acoustic signal equal in frequency to the center frequency.