The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Engineering Physics and Mathematics for public examination and debate in Auditorium F1 at Helsinki University of Technology (Espoo, Finland) on the 12th of January, 2001, at 12 o'clock noon.
Overview in PDF format (ISBN 951-22-5338-0) [1835 KB]
Dissertation is also available in print (ISBN 951-22-5276-7)
This 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.
This thesis consists of an overview and of the following 6 publications:
Keywords: surface-acoustic wave, SAW resonators, SAW filters
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© 2001 Helsinki University of Technology