Temperature compensated surface acoustic wave devices
AssigneeRaytheon Company
InventorsCharles B. Willingham, Thomas E. Parker, Frank H. Spooner
Life of this patent
Estimating the term…
Abstract
A temperature compensated surface acoustic wave device having an SiO.sub.2 film layer upon a substrate of piezoelectric material. The positive temperature coefficient of delay of the piezoelectric substrate is counterbalanced by the negative temperature coefficient of the SiO.sub.2 layer. The thickness and shape of the SiO.sub.2 layer are chosen to give a zero first order temperature coefficient for the composite device. Lithium niobate and lithium tantalate are preferred piezoelectric materials for the substrate. A high degree of temperature stability is thereby obtained with coupling coefficients much greater than were previously obtained by prior temperature compensated surface acoustic wave devices.
Claims39
In combination:
- a substrate of lithium tantalate piezoelectric material;
- and
- a layer of silicon dioxide disposed upon a surface of said substrate, the thickness of said layer being determined such that the temperature coefficient of delay for surface waves on said substrate is within a predetermined range of values.
A surface acoustic wave device comprising in combination:
- a substrate of lithium tantalate;
- one or more transducer means coupled to said substrate upon a surface thereof;
- and
- a layer of silicon dioxide disposed upon said surface of said substrate, the thickness of said layer being determined such that the temperature coefficient of delay for surface waves on said substrate is a minimum.
A surface acoustic wave device comprising in combination:
- a substrate of lithium niobate;
- one or more transducer means coupled to said substrate upon a surface thereof;
- and
- a layer of silicon dioxide disposed upon said surface of said substrate, the thickness of said layer being determined such that the temperature coefficient of delay for surface waves on said substrate is a minimum.
In combination:
- a substrate of piezoelectric material;
- input and output transducer means coupled to a surface of said substrate, said input and output transducer means each comprising a plurality of interleaved conductive fingers, the propagation time of surface waves between said input and output transducer means being dependent upon the frequency of said waves;
- a layer of silicon dioxide covering said surface and said transducer means, the thickness of said layer being determined such that the temperature coefficient of delay of said surface waves is a minimum.
In combination:
- a substrate of piezoelectric material;
- means for reflecting surface waves, said reflecting means being located upon a surface of said substrate;
- a plurality of input and output transducer means coupled to said surface and located between said reflecting means;
- and
- a layer of silicon dioxide covering said surface, said reflecting means, and said transducer means, the thickness of said layer being determined such that the temperature coefficient of delay of said surface waves is a minimum.
The method comprising the steps of:
- providing a substrate of piezoelectric material;
- fabricating one or more transducer means upon a surface of said substrate depositing a layer of silicon dioxide over said surface of said substrate and said transducer means, the thickness of said layer being determined such that the temperature coefficient of delay for acoustic waves on said surface is a minimum.
An oscillator comprising in combination:
- a substrate of piezoelectric material;
- a plurality of transducer means coupled to a surface of said substrate;
- a layer of silicon dioxide covering said surface and said transducer means, the thickness of said layer being determined such that the temperature coefficient of delay of surface waves upon said substrate is a minimum;
- and
- amplifying means, inputs of said amplifying means being coupled to one or more of said transducer means and outputs of said amplifying means being coupled to one or more other ones of said transducer means.
In combination:
- a substrate of piezoelectric material;
- and
- a layer of silicon dioxide disposed upon a surface of said substrate, the thickness of said layer being determined such that the first order temperature coefficient of delay for surface waves on said substrate is substantially zero.
In combination:
- a substrate of lithium niobate piezoelectric material;
- and
- a layer of silicon dioxide disposed upon a surface of said substrate, the thickness of said layer being determined such that the first order temperature coefficient of delay for surface waves on said substrate is substantially zero.
Dependencies are inferred from the claim text.