SAW filter operable in a piston mode
AssigneeTriQuint Semiconductor, Inc.
InventorMarc Solal
Life of this patent
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Abstract
A SAW transducer includes a pair of opposing bus bars formed on a surface of a piezoelectric substrate with a plurality of interdigital electrodes extending from each of the opposing bus bars. A center region and opposing edge regions are formed, wherein each edge region is proximate each bus bar and includes free end portions of the electrodes such that a wave velocity in each edge region is substantially lower than a wave velocity in the bus bars and in the center region, and wherein electro-acoustic sources extend into the edge regions for providing a SAW transducer having the piezoelectrically excited strongest mode is a piston mode with an amplitude distribution generally flat across most of the resonator area.
Claims18
A SAW transducer comprising;
- a piezoelectric substrate;
- a pair of opposing bus bars formed on a surface of the substrate;
- and
- a plurality of interdigital electrodes extending from each of the opposing bus bars, wherein a center region and opposing edge regions including portions of the electrodes are formed along a wave propagation axis,
- wherein each edge region is formed proximate each bus bar and includes portions of the electrodes within the edge region such that a wave velocity in each edge region is substantially lower than a wave velocity in the bus bars and in the center region, and wherein electro-acoustic sources extend from the center region into the edge regions, thus defining a source aperture of the transducer.
A SAW transducer according to 1, wherein a metal thickness of the electrode portions in the edge region is greater than the metal thickness of the electrodes in the center region so as to result in the substantially lower velocity in the edge region.
A SAW transducer comprising;
- a piezoelectric substrate;
- a pair of opposing bus bars formed on a surface of the substrate;
- and
- a plurality of interdigital electrodes extending from each of the opposing bus bars, at least a portion of the plurality of interdigital electrodes having ends attached to the opposing bus bars and free ends displaced from the opposing bus bars,
- wherein an edge region of the electrodes is formed along a wave propagation axis proximate each of the opposing bus bars and a center region thereof is formed between the edge regions,
- wherein electrode portions within each edge region comprise at least one of a metal thickness greater than the metal thickness of the electrode portion within the center region, a width greater than the width of the electrode portion within the center region, and a dielectric layer thereon and not on the electrode portion within the center region, and
- wherein the electrode portions within the edge regions support a wave velocity in each edge region substantially lower than a wave velocity in the opposing bus bars and within the center region.
Dependencies are inferred from the claim text.