Temperature compensated acoustic surface wave device

Claim 2

A temperature compensated surface wave device comprising: a substrate capable of supporting surface waves of at least a predetermined frequency; means for reducing the temperature coefficient of delay time of said device comprising an overlay layer having a predetermined thickness and contacting said substrate; and an electrode structure contacting said substrate and/or said layer for intercoupling electrical signals and said surface waves.

Claim 3

A temperature compensated surface wave device in accordance with claim 1 wherein said temperature coefficient of delay is substantially zero at said frequency.

Claim 4

A temperature compensated surface wave device in accordance with claim 1 wherein said temperature coefficient of delay is within a predetermined range of values.

Claim 5

A temperature compensated surface wave device in accordance with claim 1 wherein said electrode structure comprises at least a transmitting and a receiving array of interdigital electrodes.

Claim 6

A temperature compensated surface wave device in accordance with claim 4 wherein said overlay layer comprises a piezoelectric material which overlays substantially all of said substrate.

Claim 7

A temperature compensated surface wave device in accordance with claim 4 wherein said overlay layer overlays only said electrode arrays.

Claim 8

A temperature compensated surface wave device in accordance with claim 5 wherein said piezoelectric material is ZnO.

Claim 9

A temperature compensated surface wave device comprising: a substrate capable of supporting surface waves of at least a predetermined frequency; an electrode structure deposited on said substrate and responsive to said surface waves; means for reducing the thermal coefficient of delay of said device comprising an overlay structure deposited upon said substrate and said electrode structure; said electrode structure comprising at least a transmitting and a receiving array of interdigital electrodes; said overlay layer comprising ZnO piezoelectric material which overlays substantially all of said substrate; and the ratio of the thickness of said ZnO layer to the wavelength of said predetermined frequency being approximately 0.27.

Claim 10

A temperature compensated surface wave device comprising: a substrate capable of supporting surface waves of at least a predetermined frequency; an electrode structure deposited on said substrate and responsive to said surface waves; means for reducing the thermal coefficient of delay of said device comprising an overlay structure deposited upon said substrate and said electrode structure; said electrode structure comprising at least a transmitting and a receiving array of interdigital electrodes; said overlay layer comprising ZnO piezoelectric material which overlays substantially all of said substrate; and the ratio of the thickness of said ZnO layer to the wavelength of said predetermined frequency being approximately 0.27.

Claim 11

A temperature compensated surface wave delay line in accordance with claim 5 wherein said piezoelectric material is CdS.

Claim 12

A temperature compensated surface wave device in accordance with claim 7 wherein said substrate is fused silica.

Claim 13

A temperature compensated surface wave device in accordance with claim 5 wherein said substrate includes a curved surface; and wherein said electrodes are deposited between said substrate and said overlay layer at an angle to the axis of said surface such that launched acoustic waves spiral around said curved surface from said transmitting electrode array to said receiving electrode array.

Claim 14

A temperature compensated surface wave device in accordance with claim 11 wherein said curved surface is the surface of a cylinder.

Claim 15

A temperature compensated surface wave device in accordance with claim 6 wherein said overlay layer comprises 2 portions, one of which overlays said transmitting array and one of which overlays said receiving array; and wherein said two portions of said overlay layer are tapered at a predetermined angle such that distortion of propagated acoustic waves between said transmitting array and said receiving array is reduced.

Claim 16

A temperature compensated surface wave device in accordance with claiM 6 further comprising: a piezoelectric substrate; and wherein said overlay layer is non-piezoelectric.

Claim 17

A temperature compensated surface wave device in accordance with claim 4 wherein the locus of the midpoints of the interdigital fingers of said transmitting and receiving arrays lie at an angle with respect to the transmitted acoustic surface wave.

Claim 18

A temperature compensated surface wave delay line comprising: a non-piezoelectric substrate capable of supporting launched surface electroacoustic waves; an electrode structure including a transmitting and a receiving array of interdigital electrodes for transmitting and receiving a predetermined bandwidth centered around a predetermined frequency; and means for reducing the temperature coefficient of delay of said line comprising at said frequency a piezoelectric overlay film deposited upon said electrode structure.

Claim 19

A temperature compensated surface wave delay line comprising: a non-piezoelectric substrate capable of supporting launched surface electroacoustic waves; an electrode structure including a transmitting and a receiving array of interdigital electrodes for transmitting and receiving a predetermined bandwidth centered around a predetermined frequency; and means for reducing the temperature coefficient of delay of said line comprising at said frequency a piezoelectric overlay film deposited upon said electrode structure.

Claim 20

A temperature compensated surface wave delay line in accordance with claim 16 wherein the thickness of said substrate is large with respect to the wavelength of said predetermined frequency.

Claim 21

In combination: first and second layers of material capable of supporting surface acoustic waves of predetermined wavelength; an electrode array deposited upon said first layer and in contact with said second layer for launching surface acoustic waves between said first and second layers; and the thickness of said second layer being sufficiently less than the thickness of said first layer to substantially reduce the temperature coefficient of delay time of said combination.

Claim 22

In combination: first and second layers of material capable of supporting surface acoustic waves of predetermined wavelength; an electrode array deposited upon said first layer and in contact with said second layer for launching surface acoustic waves between said first and second layers; and the thickness of said second layer being sufficiently less than the thickness of said first layer to substantially reduce the temperature coefficient of delay time of said combination.

Claim 23

A combination in accordance with claim 18 wherein said first layer is a non-piezoelectric substrate and wherein said second layer is a piezoelectric overlay film.

Claim 24

A combination in accordance with claim 18 wherein said first and said second layers are piezoelectric material.

Claim 25

A combination in accordance with claim 19 wherein said piezoelectric material is zinc oxide and wherein said substrate is fused silica.

Claim 26

A combination in accordance with claim 19 wherein said electrode array is in contact only with said second layer.

Claim 27

A temperature compensated surface wave delay device comprising: a non-piezoelectric substrate having deposited thereon at least a transmitting interdigital electrode array and a receiving interdigital electrode array, said substrate having a thermal expansion coefficient Alpha ; a piezoelectric substrate in contact with said non-piezoelectric substrate, said piezoelectric substrate having a surface acoustic wave temperature coefficient of velocity Tv; and wherein Alpha Tv .

Claim 28

A temperature compensated surface wave delay device comprising: a non-piezoelectric substrate having deposited thereon at least a transmitting interdigital electrode array and a receiving interdigital electrode array, said substrate having a thermal expansion coefficient Alpha ; a piezoelectric substrate in contact with said non-piezoelectric substrate, said piezoelectric substrate having a surface acoustic wave temperature coefficient of velocity Tv; and wherein Alpha Tv .

Claim 29

A temperature compensated surface wave delay device comprising: at least two non-piezoelectric substrates having deposited thereon at least a transmitting interdigital electrode array and a receiving interdigital electrode array, said substrates having thermal expansion coefficients Alpha 1, and Alpha 2; a piezoelectric substrate in contact with said non-piezoelectric substrates, said piezoelectric substrate having a thermal expansion coefficient Alpha 3 such that Alpha 3 is less than Alpha 1 and such that Alpha 3 is less than Alpha 2, said piezoelectric substrate having a surface acoustic wave temperature coefficient Tv; means for maintaining separation of said non-piezoelectric substrates such that pressure is exerted on said piezoelectric substrate; and wherein said surface wave device has an effective temperature coefficient 1/l dl/dT where l is the separation between said transmitting and receiving electrode arrays and T is temperature and wherein 1/l dl/dT Tv .

Claim 30

A temperature compensated surface wave delay device comprising: at least two non-piezoelectric substrates having deposited thereon at least a transmitting interdigital electrode array and a receiving interdigital electrode array, said substrates having thermal expansion coefficients Alpha 1, and Alpha 2; a piezoelectric substrate in contact with said non-piezoelectric substrates, said piezoelectric substrate having a thermal expansion coefficient Alpha 3 such that Alpha 3 is less than Alpha 1 and such that Alpha 3 is less than Alpha 2, said piezoelectric substrate having a surface acoustic wave temperature coefficient Tv; means for maintaining separation of said non-piezoelectric substrates such that pressure is exerted on said piezoelectric substrate; and wherein said surface wave device has an effective temperature coefficient 1/l dl/dT where l is the separation between said transmitting and receiving electrode arrays and T is temperature and wherein 1/l dl/dT Tv .

Claim 31

A temperature compensated surface wave delay device in accordance with claim 24 wherein: Alpha 1 Alpha 2 .