Decoupled stacked bulk acoustic resonator band-pass filter with controllable pass bandwith
First Claim
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1. A band-pass filter characterized by a center frequency, the 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 single layer of acoustic decoupling material, the layer of acoustic decoupling material having a nominal thickness equal to an odd integral multiple of 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 comprising at least one of polyimide, poly(para-xylylene) and a crosslinked polyphenylene polymer.
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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.
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Citations
9 Claims
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1. 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 element between the electrodes; and between the FBARs, an acoustic decoupler comprising a single layer of acoustic decoupling material, the layer of acoustic decoupling material having a nominal thickness equal to an odd integral multiple of 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 comprising at least one of polyimide, poly(para-xylylene) and a crosslinked polyphenylene polymer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification