Embodiments of an acoustically-coupled transformer have a first stacked bulk acoustic resonator (SBAR) and a second SBAR. Each of the SBARs has a lower film bulk acoustic resonator (FBAR) and an upper FBAR, and an acoustic decoupler between the FBARs. The upper FBAR is stacked atop the lower FBAR. Each FBAR has opposed planar electrodes and a piezoelectric element between the electrodes. The piezoelectric element is characterized by a c-axis. 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. The transformer additionally has 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.