NDLI: FEM/BEM impedance and power analysis for measured LGS SH-SAW devices

Content Provider	IEEE Xplore Digital Library
Author	Kenny, T.D. Pollard, T.B. Berkenpas, E.J. da Cunha, M.P.
Copyright Year	2005
Description	Author affiliation: Dept. of Electr. & Comput. Eng., Maine Univ., Orono, ME, USA (Kenny, T.D.; Pollard, T.B.; Berkenpas, E.J.; da Cunha, M.P.)
Abstract	Pure shear horizontal surface acoustic waves (SH-SAW) exist on rotated Y-cuts, Euler angles (0/spl deg/, 0, 90/spl deg/), of trigonal class 32 group crystals, which include quartz and the LGX family of crystals (langasite, langatate, and langanite). This pure SH-SAW mode has a number of interesting propagation characteristics. Along selected LGX orientations, interdigital transducers (IDTs) used to generate the SH-SAW also excite a significant amount of shear horizontal bulk acoustic wave (SH-BAW) that propagates almost parallel to the surface, with a slightly different phase velocity. We use combined finite and boundary element methods (FEM/BEM) to calculate IDT admittance, while considering both the SH-SAW and SH-BAW contribution. The ratio of transduced SH-SAW power to total input power is analyzed as a function of device geometry and IDT metallization material and thickness. Typically, for a 20/spl lambda/ IDT, the FEM/BEM simulations indicate that about 40% of input power is converted to the SH-SAW when the area outside of the IDT is coated with an infinitesimally thin conducting film. Both our simulations and experimental results consistently indicate that the ratio of SH-SAW to total input power strongly depends on metal type and thickness. The SH-BAW angular plots obtained with the FEM/BEM analysis confirm that the mode excited by the IDTs propagates nearly parallel to the surface. Measured device impedances agree extremely well (within 5%) with the FEM/BEM IDT impedance calculations accounting for both SH-SAW and SH-BAW generation.
Starting Page	1371
Ending Page	1374
File Size	662974
Page Count	4
File Format	PDF
ISBN	0780384121
ISSN	10510117
DOI	10.1109/ULTSYM.2004.1418051
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2004-08-23
Publisher Place	Canada
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Impedance measurement Power measurement Surface impedance Surface acoustic wave devices Acoustic waves Crystals Acoustic propagation Acoustic measurements Acoustic transducers Boundary element methods
Content Type	Text
Resource Type	Article

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