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.
Aalto

Numerical Simulations of Microacoustic Resonators and Filters

Tapani Makkonen

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 29th of April, 2005, at 12 o'clock noon.

Overview in PDF format (ISBN 951-22-7636-4)   [1923 KB]
Dissertation is also available in print (ISBN 951-22-7635-6)

Abstract

This dissertation discusses numerical simulations of microwave acoustic resonators and bandpass filters employed in wireless telecommunication systems. In the first part of the dissertation, tailored finite element method (FEM) software with efficient numerical techniques is implemented and applied in the modeling of thin-film bulk-acoustic wave resonators (FBARs). Simulations with 3D FEM models of FBARs are carried out to investigate the effect of the electrode shape on the spurious resonances that often are present in the electrical response. The modeling results are validated through comparison of simulated and measured mechanical vibration amplitudes. The usability of the FEM tool is further demonstrated in simulations of a resonator design that features a clean electrical frequency response, free of spurious resonance peaks caused by anharmonic modes. Additionally, a method is proposed for determination of the elastic constants of a piezoelectric thin-film material. The technique is based on fitting of the computed dispersion curves of Lamb-wave modes to those measured from an FBAR using a scanning laser interferometer.

In the second part of this dissertation, numerical simulations are used to study propagation properties of longitudinal leaky surface acoustic wave (LLSAW) mode under periodic electrode array on YZ-cut lithium niobate (LN). A combined FEM/boundary element method is employed to compute the electric admittance of one-port synchronous LLSAW resonators. Simulations and experiments are used to derive the dependence of the resonator resonance frequencies and Q values on the electrode dimensions. Ladder-type bandpass filters exploiting the LLSAW mode are implemented on YZ-cut LN in the frequency range from 2.5 GHz to 5.2 GHz, with fundamental mode LLSAW resonators as building blocks. The results demonstrate that the high phase velocity of the LLSAW mode on YZ-cut LN allows inexpensive fabrication of wide-band, low-loss filters up to 5 GHz using conventional optical lithography.

The third topic considered is comprehensive modeling of a SAW duplexer, including electromagnetic modeling of the ceramic package. The parasitic capacitive and inductive couplings in the package are obtained using rigorous computation, allowing one to estimate the package effects on the duplexer performance.

This thesis consists of an overview and of the following 6 publications:

  1. T. Makkonen, A. Holappa, J. Ellä, and M. M. Salomaa. 2001. Finite element simulations of thin-film composite BAW resonators. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 48, pages 1241-1258. © 2001 IEEE. By permission.
  2. T. Makkonen, T. Pensala, J. Vartiainen, J. V. Knuuttila, J. Kaitila, and M. M. Salomaa. 2004. Estimating materials parameters in thin-film BAW resonators using measured dispersion curves. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 51, pages 42-51. © 2004 IEEE. By permission.
  3. T. Makkonen, V. P. Plessky, W. Steichen, V. I. Grigorievski, M. Solal, and M. M. Salomaa. Longitudinal leaky SAW resonators and filters on YZ-LiNbO3. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, accepted for publication. © 2005 IEEE. By permission.
  4. T. Makkonen, V. P. Plessky, W. Steichen, and M. M. Salomaa. 2003. Surface-acoustic-wave devices for the 2.5-5 GHz frequency range based on longitudinal leaky waves. Applied Physics Letters 82, pages 3351-3353. © 2003 American Institute of Physics. By permission.
  5. T. Makkonen, V. P. Plessky, W. Steichen, S. Chamaly, C. Poirel, M. Solal, and M. M. Salomaa. 2003. Fundamental mode 5 GHz surface-acoustic-wave filters using optical lithography. Applied Physics Letters 83, pages 3596-3598. © 2003 American Institute of Physics. By permission.
  6. T. Makkonen, S. Kondratiev, V. P. Plessky, T. Thorvaldsson, J. Koskela, J. V. Knuuttila, and M. M. Salomaa. 2001. Surface acoustic wave impedance element ISM duplexer: modeling and optical analysis. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 48, pages 652-665. © 2001 IEEE. By permission.

Errata of publications 1, 2 and 4

Keywords: finite element method, thin-film bulk acoustic wave resonator, surface acoustic wave, bandpass filter

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© 2005 Helsinki University of Technology

Last update 2011-05-26