Patent ID: 7091649

Claim:
An acoustically-coupled transformer, comprising: a first stacked bulk acoustic resonator (SBAR) and a second SBAR, each SBAR comprising: a lower film bulk acoustic resonator (FBAR) and an upper FBAR, the upper FBAR stacked atop the lower FBAR. each FBAR comprising opposed planar electrodes and a piezoelectric element between the electrodes, the piezoelectric element characterized by a c-axis, an acoustic decoupler between the FBARs, in which the c-axes of the piezoelectric elements of the lower FBARs are opposite in direction and the c-axes of the piezoelectric elements of the upper FBARs are opposite in direction; a first electrical circuit connecting the lower FBAR of the first SBAR to the lower FBAR of the second SBAR; and a second electrical circuit connecting the upper FBAR of the first SBAR to the upper FBARS of the second SBAR.