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US 6,054,794 AGranted
Optimal cut for wave propagation surface on langanite substrate
AssigneeSawtek, Inc.
InventorsNatalya F. Naumenko, Leland P. Solie
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AssigneeSawtek, Inc.
InventorsNatalya F. Naumenko, Leland P. Solie
Estimating the term…
A lanthanum gallium niobate single crystal substrate, referred to as langanite, has a prescribed range of Euler angles for substrate and crystal orientation for improving signal processing for a surface acoustic wave (SAW) device. When a voltage is applied to an input interdigital transducer (IDT) of the SAW device, a surface acoustic wave is generated in the langanite piezoelectric substrate. The surface acoustic wave propagates in a direction generally perpendicular to electrodes of the IDT. The langanite crystal cut and wave propagation directions are defined which reduce insertion loss and frequency response distortion due to SAW transduction, diffraction, and beam steering, while achieving improved temperature stability SAW device as compared to other commonly used crystal substrates. A low power flow angle and reduced level of diffraction is also achieved.
A lanthanum gallium niobate (langanite) substrate comprising a planar surface formed from a cut of the substrate, wherein a direction of propagation of a wave along the planar surface of the substrate is defined to be along an X' axis, a Z' axis is defined as being normal to the propagation surface, and a Y' axis is defined to be along the propagation surface and perpendicular to the X' axis, and wherein a crystal orientation for the substrate is defined by crystal axes X, Y, and Z, having a relative orientation to X', Y', and Z' substrate axes defined by Euler angles .PHI. and .THETA., with .PHI. having a value ranging from -5.degree. to 5.degree., and .theta. having a value ranging from 130.degree. to 150.degree..
A surface acoustic wave device substrate formed from a lanthanum gallium niobate (langanite) single crystal, the substrate comprising a planar surface for receiving one or more interdigital transducers having a plurality of electrodes, the interdigital transducers operable for launching and detecting surface acoustic waves propagating generally perpendicular to the electrodes, wherein the substrate comprises a crystal orientation cut for forming the planar surface, the crystal orientation defined by Euler angles .PHI. and .theta., where .PHI. and .theta. define a surface which is crystallographically equivalent to the surface defined by .PHI. having a value ranging from approximately -5.degree. to approximately 5.degree. and .theta. having a value ranging from approximately 130.degree. to approximately 150.degree..
A method for forming a surface acoustic wave device substrate comprising the steps of providing a lanthanum gallium niobate (langanite) single crystal, orientating the crystal for cutting a planar surface, the crystal orientating defined by Euler angles .PHI., .theta., and .psi., and cutting the crystal for forming the planar surface with a defined direction of propagation, the cut defined by the Euler angles, wherein .PHI. has a value ranging from approximately -5.degree. to approximately 5.degree., and .theta. has a value ranging from approximately 130.degree. to approximately 150.degree..
Dependencies are inferred from the claim text.