Decoupled stacked bulk acoustic resonator band-pass filter with controllable pass bandwidth
First Claim
Patent Images
1. A band-pass filter, comprising:
- a lower film bulk acoustic resonator (FBAR), an upper FBAR stacked on the lower FBAR, each FBAR comprising opposed planar electrodes and a piezoelectric element between the electrodes; and
between the FBARs, an acoustic decoupler comprising a layer of acoustic decoupling material.
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Abstract
The band-pass filter has an upper film bulk acoustic resonator (FBAR), an upper FBAR stacked on the lower FBAR, and, between the FBARs, an acoustic decoupler comprising a layer of acoustic decoupling material. Each of the FBARs has opposed planar electrodes and a piezoelectric element between the electrodes. The acoustic decoupler controls the coupling of acoustic energy between the FBARs. Specifically, the acoustic decoupler couples less acoustic energy between the FBARs than would be coupled by direct contact between the FBARs. The reduced acoustic coupling gives the band-pass filter desirable in-band and out-of-band properties.
185 Citations
25 Claims
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1. A band-pass filter, comprising:
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a lower film bulk acoustic resonator (FBAR), an upper FBAR stacked on the lower FBAR, each FBAR comprising opposed planar electrodes and a piezoelectric element between the electrodes; and
between the FBARs, an acoustic decoupler comprising a layer of acoustic decoupling material. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. The band-pass filter of claim 22, in which the crosslinked polyphenylene polymer is formed from a precursor solution sold by The Dow Chemical Company under the trademark SiLK.
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23. A band-pass filter characterized by a center frequency, the band-pass filter comprising:
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a lower film bulk acoustic resonator (FBAR), an upper FBAR stacked on the lower FBAR, each FBAR comprising opposed planar electrodes and a piezoelectric 5 element between the electrodes; and
between the FBARs, a layer of acoustic decoupling material having a nominal thickness equal to one quarter of the wavelength in the acoustic decoupling material of an acoustic signal equal in frequency to the center frequency, the acoustic decoupling material lower in acoustic impedance than piezoelectric element. - View Dependent Claims (24)
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25. A band-pass filter, comprising:
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a lower film bulk acoustic resonator (FBAR), an upper FBAR stacked on the lower FBAR, each FBAR comprising opposed planar electrodes and a piezoelectric element between the electrodes; and
between the FBARs, an acoustic decoupler comprising an acoustic decoupling layer of an acoustic decoupling material having an acoustic impedance of about 2 Mrayl.
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Specification