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.
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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 Large Seminar Hall of Micronova at Helsinki University of Technology (Espoo, Finland) on the 1st of November, 2006, at 12 o'clock noon.
Overview in PDF format (ISBN 951-38-6866-4) [846 KB]
VTT Publications 616, ISSN 1455-0849
Dissertation is also available in print (ISBN 951-38-6865-6)
Copyright © 2006 VTT Technical Research Centre of Finland
VTT Publications 616, ISSN 1235-0621
VTT-PUBS-616
TKK-DISS-2202
Starting in the early 1960's, when the integrated-circuit (IC) technology was developed, micromachining and microelectromechanical systems (MEMS) have grown into a broad research field with several commercial successes. Typical applications of MEMS are in physical, chemical and biochemical sensors, as well as in optical systems such as the digital micromirror device of Texas Instruments. From the 1990's, the advances in the processing technologies and the tremendous growth of the wireless-communication market have drawn much interest into radio-frequency MEMS devices (RF MEMS) such as filters, oscillators, switches and tunable capacitors. These are now beginning to penetrate the market.
This thesis considers electrostatically-actuated RF-MEMS filters and delay lines. For filters, the work concentrates on nonlinear distortion and filter design. The intermodulation properties of capacitively-coupled MEMS filters are analytically solved in closed form and the theory is verified in numerical simulations as well as in measurements with MEMS resonators. The analysis is more generally valid than the previously published results. The theory is utilized to formulate a design procedure for MEMS filters that, for the first time, takes systems speci-fications for tolerable intermodulation distortion and insertion-loss into account. For delay lines, capacitive actuation of bulk-acoustic waves in a solid rod is analyzed. In particular, challenges in impedance matching due to the weakness of the electrostatic coupling are quantified. Finally, a new kind of resonator-chain delay line for high-frequency (HF) signals is introduced. This delay line is characterized by extremely slow signal group velocity (∼ 10-100 m/s), narrow-band response, and much lower characteristic impedance than found for the solid-rod waveguide enabling efficient signal coupling. Properties of the resonator-chain waveguide are theoretically analyzed and the results are verified in measurements of fabricated devices.
This thesis consists of an overview and of the following 6 publications:
Keywords: MEMS, radio-frequency MEMS, microelectromechanical filters, microelectromechanical resonators, components, transducers, wireless communication, transmission lines, acoustic wave propagation, intermodulation
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© 2006 Helsinki University of Technology