Patent ID: 6987433

Claim:
An acoustically-coupled transformer, comprising: a first stacked bulk acoustic resonator and a second stacked bulk acoustic resonator (SBAR), each SBAR comprising: a stacked pair of film bulk acoustic resonators (FBARs), each of the FBARs comprising opposed planar electrodes and a layer of piezoelectric material between the electrodes, the piezoelectric material having a c-axis, and an acoustic decoupler between the FBARs; a first electrical circuit connecting one of the FBARs of the first SBAR to one of the FBARs of the second SBAR; and a second electrical circuit connecting the other of the FBARs of the first SBAR to the other of the FBARs of the second SBAR, in which the c-axis of the piezoelectric material of one of the FBARs is opposite in direction to the c-axes of the piezoelectric material of the other three FBARs.