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US 5,307,035 AGranted
Low loss surface wave filter
AssigneeThomson-CSF
InventorsPierre Dufilie, Jean-Michel Hode
Life of this patent
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Abstract
A low loss microwave surface acoustic wave filter, comprising input (2, 3) and output (4, 5) transducers, acoustically associated with coupling transducers (6, 7). The relative positions of the transducers 2 to 7) and of their O reflectors are chosen, having regard to the weightings of the coupling transducers (6, 7) in order to obtain the desired transfer function for this filter.
Claims7
A surface wave filter comprising:
- at least one input transducer;
- at least one first coupling transducer acoustically connected to the at least one input transducer;
- at least one second coupling transducer electrically connected to the at least one first coupling transducer;
- at least one output transducer acoustically connected to the at least one second coupling transducer;
- wherein at least one of the at least one input transducer or the at least one output transducer comprises a central transducer element and a coupler surrounding the central transducer element, wherein the central transducer element is offset with respect to an axis of the coupler normal to a direction of propagation of a surface wave by a distance i, where
- i=.lambda./8+N .lambda./2
- where
- .lambda. is a propagation wavelength of the surface wave, and
- N is a non-zero integer.
6 more elements
A surface wave filter comprising:
- two input transducers;
- at least one first coupling transducer acoustically connected to the two input transducers;
- at least one second coupling transducer electrically connected by a metal strip to the at least one first coupling transducer;
- two output transducers acoustically connected to the at least one second coupling transducer;
- wherein the two input transducers and the two output transducers each comprise a central transducer element and a coupler surrounding the central transducer element;
- wherein for at least one of the two input or two output transducers the central transducer element is offset with respect to a central axis of the coupler normal to a direction of propagation of a surface wave by a distance i, where
- i=.lambda./8+N/ .lambda.2
- where
- .lambda. is a propagation wavelength of the surface wave, and
- N is a non-zero integer.
7 more elements
Dependencies are inferred from the claim text.