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US 6,650,207 B1Granted
Longitudinally coupled surface acoustic wave filter with linearly weighted reflectors
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorHiroshi Tanaka
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Abstract
In a longitudinally coupled multi-mode surface acoustic wave filter which has an assembly of more than two interdigital transducers formed on a piezoelectric substrate and reflectors composed of shorted grating electrodes different in pitch from the IDTs. The grating electrodes are weighted so that their numbers vary linearly with the position in the direction perpendicular to the direction of propagation of surface acoustic waves.
Claims3
A longitudinally coupled surface acoustic wave filter comprising:
- a piezoelectric substrate;
- at least two interdigital transducers formed over the piezoelectric substrate;
- and
- reflectors disposed on both sides of said at least two interdigital transducers, wherein:
- said reflectors each have at least a weighted portion including electrodes weighted so that a number of said electrodes varies linearly with a position in a direction perpendicular to a direction of propagation of surface acoustic waves, and bus bars for shorting said weighted electrodes, and
- a value of M/L is greater than or equal to 0.3,
- where M denotes a length of the weighted portion of a respective reflector in the direction of propagation of the surface acoustic waves, and L denotes a total length of the respective reflector in the direction of propagation of the surface acoustic waves.
4 more elements
Dependencies are inferred from the claim text.