Impedance transforming bulk acoustic wave baluns

摘要

A bulk acoustic wave device includes an acoustic decoupler between first and second film bulk acoustic resonators (FBARs). The first FBAR is resonant at a resonant frequency of the device and includes first and second planar electrodes abutting opposite sides of a first resonator volume free of any intervening electrodes and containing piezoelectric material disposed for acoustic vibrations parallel to a propagation axis normal to the first and second electrodes. The first FBAR has a first electrical impedance parallel to the propagation axis. The second FBAR is resonant at the resonant frequency and includes third and fourth planar electrodes abutting opposite sides of a second resonator volume free of any intervening electrodes and containing piezoelectric material disposed for acoustic vibrations parallel to the propagation axis. The second FBAR has a second electrical impedance parallel to the propagation axis and different from the first electrical impedance.