Impedance matching and parasitic capacitor resonance of FBAR resonators and coupled filters

摘要

A film acoustically-coupled transformer (FACT) has a first and a second stacked bulk acoustic resonator (SBAR 1, SBAR 2). Each SBAR has a stacked pair of film bulk acoustic resonators (FBARs) and an acoustic decoupler between the FBARs. Each FBAR has opposed planar electrodes and a layer of piezoelectric material between the electrodes. A first electrical circuit connecting one of the FBARs of SBAR1 to one of the FBARs of SBAR 2 and a second electrical circuit connecting the other of the FBARs of SBAR 1 to the other of the FBARs of SBAR 2. The first electrical circuit connects the respective FBARs in parallel and second electrical circuit connects the respective FBARs in series. A shunt inductor is included from the reception path to ground.