Wave transmission lines and networks – Coupling networks – Electromechanical filter
Reexamination Certificate
2011-08-30
2011-08-30
Summons, Barbara (Department: 2817)
Wave transmission lines and networks
Coupling networks
Electromechanical filter
C333S189000, C310S312000, C310S326000
Reexamination Certificate
active
08008993
ABSTRACT:
A thin-film bulk acoustic wave (BAW) resonator, such as SBAR or FBAR, for use in RF selectivity filters operating at frequencies of the order of 1 GHz. The BAW resonator comprises a piezoelectric layer (14) having first and second surfaces on opposing sides, a first electrode (16) extending over the first surface, and a second electrode (12) extending over the second surface, the extent of the area of overlap (R1) of the first and second electrodes determining the region of excitation of the fundamental thickness extensional (TE) mode of the resonator. The insertion loss to the resonator is reduced by providing a dielectric material (18) in the same layer as the first electrode (16) and surrounding that electrode. The material constituting the dielectric material (18) has a different mass, typically between 5% and 15%, from the material comprising the first electrode (16) it surrounds. The mass of the dielectric material (18) can be lower or higher than the mass of the first electrode (16). Planarisation of the dielectric material (18) enhances the performance of the device.
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Kaitila, J; et al “Spurious Resonance Free Bulk Acoustic Wave Resonators” IEEE Ultrasonics Symposium 2003, Honolulu, HI, vol. 1, Oct. 2003, pp. 84-87.
Milsom, R. F; et al “Combined Acoustic-Electromagnetic Simulation of Thin-Film Bulk Acoustic Wave Filters” IEEE Ultrasonics Symposium 2002, vol. 1, October 2002, pp. 989-994.
Loebl, H-P; et al “Solidly Mounted Bulk Acoustic Wave (BAW) Filters for the Ghz Frequency Range” IEEE Ultrasonics Symposium 2002, vol. 1, Oct. 2002, pp. 919-923.
Jansman Andreas Bernardus Maria
Loebl Hans-Peter
Milsom Robert Frederick
Ruigrok Jaap
Vanhelmont Frederik Willem Maurits
NXP B.V.
Summons Barbara
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