Acoustic wave devices employing surface skimming bulk waves

Abstract

An acoustic wave device employing surfaces skimming bulk waves comprises a piezo electric substrate having a flat surface which carries an input transducer and an output transducer for respectively lanuching and receiving acoustic waves into and from the bulk of the substrate. The substrate may be of quartz, lithium tantalate, or lithium niobate and has the flat surface orientated so that a surface skimming bulk wave is launched without generation of surface acoustic waves.

I claim: 
     
       1. An acoustic wave device employing surface skimming bulk waves, comprising a piezo electric substrate having a flat surface and an input transducer and an output transducer mounted on said flat surface for respectively launching acoustic waves in and receiving acoustic waves from the substrate, the substrate having an orientation of said flat surface which is a rotated, about the crystalline X axis, Y cut material, said substrate and its associated transducers being selected from one of the following groups: (a) a quartz substrate with the rotation of cut about the X axis being in the range -60° to -45° and 30° to 40°, and with said transducers being so arranged on said surface that propagation of the acoustic wave vector is perpendicular to the X axis; and   (b) a lithium tantalate substrate with the rotation of cut about the X axis being in the ranges 33° to 39° and -51° to -57°, and with said transducers being so arranged on said surface that propagation of the acoustic wave vector is parallel to the Y axis.   
     
     
       2. A device according to claim 1 wherein the substrate is quartz and the rotation of cut is in the range -55° to -48° inclusive. 
     
     
       3. A device according to claim 1 wherein the substrate is quartz and the rotation of cut is in the range -51° to -49° inclusive. 
     
     
       4. A device according to claim 1 wherein the substrate has a face opposite said flat surface which is not parallel to said flat surface. 
     
     
       5. A device according to claim 1 wherein the transducers are interdigital finger comb transducers. .Iadd. 
     
     
       6.  An acoustic wave device employing surface skimming bulk waves, comprising a piezo electric substrate having a flat surface and an input transducer and an output transducer mounted on said flat surface for respectively launching acoustic waves in and receiving acoustic waves from the substrate, the substrate having an orientation of said flat surface which is rotated, about the crystalline X axis, Y-cut material, said substrate and its associated transducers is a lithium substrate with the rotation of cut about the X axis being approximately 36°, and with said transducers being so arranged on said surface that propagation of the acoustic wave vector is parallel to the X axis. .Iaddend. .Iadd.7. A device according to claim 6, wherein the substrate has a face opposite said flat surface which is not parallel to said flat surface. .Iaddend. .Iadd.8. A device according to claim 6, wherein the transducers are interdigital finger comb transducers. .Iaddend. .Iadd.9. An acoustic wave device employing surface skimming bulk waves, comprising a piezo electric substrate having a flat surface and an input transducer and an output transducer mounted on said flat surface for respectively launching acoustic waves in and receiving acoustic waves from the substrate, the substrate having an orientation of said flat surface which is rotated, about the crystalline X axis, Y-cut material, said substrate and its associated transducers is a lithium tantalate substrate with the rotation of cut about the X axis being 36° and with said transducers being so arranged on said surface that propagation of the acoustic wave vector 
     
     
        is parallel to the X axis. .Iaddend. .Iadd.10.  A device according to claim 9, wherein the substrate has a face opposite said flat surface which is not parallel to said flat surface. .Iaddend. .Iadd.11. A device according to claim 9, wherein the transducers are interdigital finger comb transducers. .Iaddend. .Iadd.12. An acoustic wave device employing surface skimming bulk waves, comprising a piezo electric substrate having a flat surface and an input transducer and an output transducer mounted on said flat surface for respectively launching acoustic waves in and receiving acoustic waves from the substrate, the substrate having an orientation of said flat surface which is rotated, about the crystalline X axis, Y-cut material, said substrate and its associated transducers in a lithium tantalate substrate with the rotation of cut about the X axis being approxiomately 36° i.e. from 33° to 39° and with said transducers being so arranged on said surface that propagation of the acoustic wave vector is parallel to the X axis. .Iaddend. .Iadd.13. A device according to claim 12, wherein the substrate has a face opposite said flat surface which is not parallel to said flat surface. .Iaddend. .Iadd.14. A device according to claim 13, wherein the transducers are interdigital finger comb transducers. .Iaddend.