Analysis and modeling of surface-acoustic wave resonators
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Doctoral thesis (article-based)
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Helsinki University of Technology publications in engineering physics. A, 804
AbstractThis thesis discusses the analysis and simulation of surface-acoustic wave (SAW) resonators. SAW resonators constitute building blocks for radio-frequency SAW bandpass filters, which are widely employed in modern cordless and cellular telecommunication systems. Theoretical tools for the analysis and simulation of SAWs and SAW resonators are vital in the development of high-performance SAW devices. The carrying theoretical concept is the excitation of acoustic waves in periodic electrode arrays. The first part of the thesis is concerned with the characterization of periodic electrode arrays with rigorous simulations. In this work a structure simulator based on combined finite-element and boundary-element methods has been implemented, and it has been applied to analyze leaky surface-acoustic waves (LSAW) in rotated Y-cut LiNbO3 and LiTaO3 substrates, and surface transverse waves (STW) in langasite. The second part of the thesis consists of contributions to phenomenological modeling. Firstly, it is shown that the parameters used in the phenomenological coupling-of-modes theory, popular in device design, may be efficiently extracted from rigorous simulations of periodic electrode arrays using a novel phase-shift algorithm. Secondly, so-called Plessky's model for the STW dispersion in periodic structures is extended into a simulation model for finite, synchronous LSAW and STW resonators. The third part of the thesis concentrates on acoustic loss mechanisms in LSAW resonators on LiTaO3 substrate. The electric losses due to various mechanisms are estimated and discussed. Most importantly, a recently observed acoustic leakage is identified as parasitic excitation of LSAWs to the busbars of the resonator.
surface-acoustic wave, SAW resonators, SAW filters
J. Koskela, V. P. Plessky, and M. M. Salomaa, Suppression of the leaky SAW attenuation with heavy mechanical loading, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 45, 439-449 (1998).
DOI: 10.1109/58.660154 View at publisher
J. Koskela, S. Lehtonen, V. P. Plessky, and M. M. Salomaa, Surface transverse waves on langasite, Applied Physics Letters 72, 2665-2667 (1998).
DOI: 10.1109/ULTSYM.1998.762118 View at publisher
J. Koskela, V. P. Plessky, and M. M. Salomaa, SAW/LSAW COM parameter extraction from computer experiments with harmonic admittance of a periodic array of electrodes, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 46, 806-816 (1999).
DOI: 10.1109/58.775644 View at publisher
J. Koskela, V. P. Plessky, and M. M. Salomaa, Theory for shear horizontal surface acoustic waves in finite synchronous resonators, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 47, 1550-1560 (2000).
DOI: 10.1109/58.883544 View at publisher
J. Koskela, J. V. Knuuttila, P. T. Tikka, C. S. Hartmann, V. P. Plessky, and M. M. Salomaa, Mechanism for acoustic leakage in surface-acoustic wave resonators on rotated Y-cut lithium tantalate substrate, Applied Physics Letters 75, 2683-2685 (1999).
DOI: 10.1063/1.125117 View at publisher
- J. Koskela, J. V. Knuuttila, T. Makkonen, V. P. Plessky, and M. M. Salomaa, Acoustic loss mechanisms in leaky SAW resonators on lithium tantalate, Report TKK-F-A801, ISBN 951-22-5142-6, submitted to IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control (2000).