Title page for ETD etd-11132007-105835


Type of Document Master's Thesis
Author Park, Seunghoon
Author's Email Address spark7@lsu.edu
URN etd-11132007-105835
Title A Study on Buckled-Beam Actuators for RF MEMS Applications
Degree Master of Science in Electrical Engineering (M.S.E.E.)
Department Electrical & Computer Engineering
Advisory Committee
Advisor Name Title
Dooyoung Hah Committee Chair
Martin Feldman Committee Member
Pratul K. Ajmera Committee Member
Keywords
  • Electromagnetic actuator
  • SU-8 LIGA
  • electroplating
Date of Defense 2007-11-06
Availability unrestricted
Abstract
When combined with MEMS actuators, a mechanical lock is a useful device for various applications including memory cells, micro-relays, micro-valves, optical switches, and digital micro-mirrors. It allows removal of actuation force during idle periods without affecting an actuated state of a device, which makes standing power consumption completely unnecessary. In this thesis, a bistable buckled-beam actuator for RF MEMS switch applications has been examined. The buckled-beam geometry was designed based upon theoretical analysis. It was fabricated by SU-8 lithography and copper pulse electroplating. It was actuated by the Lorentz force using external magnet and current flow through the beam. Measured switching currents (10 to 200 mA) agree well with theoretical values. Required actuation voltage was less than 0.4 V for 20 to 60 μm displacement.

The developed buckled-beams were incorporated into a RF MEMS switch design. The basic structure of the proposed switch is a combination of a coplanar waveguide and two buckled-beam actuators. The coplanar waveguide has a ground-signal-ground (GSG) configuration and its dimensions were designed for 50 ohm characteristic impedance over broad RF band. The proposed switch has several advantages compared to the conventional capacitive-type RF MEMS switches. First, since the electromagnetic actuation mechanism is adopted in the proposed switch, required actuation voltage is much lower than the electrostatic actuation mechanism. Second, all the structures can be made from the same layer so that only one mask is necessary for the entire process. Third, the trapped charge issue is dramatically diminished because the actuators are separated from the coplanar waveguide, very low voltage is applied to the actuators, and the polarity of voltage on the actuators is continuously toggled.

The proposed RF MEMS switch finds a variety of usefulness in RF circuits and systems, including wireless communication devices – antenna switching, T/R (transmitter/receiver) switching, band selection, adjustable gain amplifiers; radar systems for military applications – phase shifters, phased array antennas; measurement equipments – impedance matching circuits, etc.

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