ACOUSTICALLY-COUPLED TRANSFORMER WITH REVERSE C-AXIS PIEZOELECTRIC MATERIAL

摘要

PROBLEM TO BE SOLVED: To provide an acoustically-coupled transformer more easily manufactured with excellent common mode rejection.

SOLUTION: The acoustically-coupled transformer has first and second stacked bulk acoustic resonators (SBARs), each having a stacked pair of film bulk acoustic resonators (FBARs) with an acoustic decoupler between the FBARs. Each FBAR has opposed planar electrodes with piezoelectric material between the electrodes. A first electrical circuit connects one of the FBARs of the first SBAR to one FBAR of the second SBAR, and a second electrical circuit connects the other FBAR of the first SBAR to the other FBAR of the second SBAR. The c-axis of the piezoelectric material of one of the FBARs is opposite in direction to the c-axes of the piezoelectric materials of the other three FBARs.

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