Radio frequency microelectromechanical systems (RF-MEMS) systems design

• Main Author: Chan, Winston Qingyao.
• Other Authors: Wang Hong
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Microelectromechanical systems; DRNTU::Engineering::Electrical and electronic engineering::Antennas, wave guides, microwaves, radar, radio
• Online Access: http://hdl.handle.net/10356/15801
• Institution: Nanyang Technological University

Radio-frequency Microelectromechanical Systems (RFMEMs) are collections of micro-scaled components such as filters and oscillators that generate electrical activity via mechanical movement and electrical excitation, composed of inductors and capacitors and widely applied in communication systems which occupy the upper end of the RF spectrum. They introduce reconfigurability and fast, accurate switching which enhances frequency selectivity. Generally, RFMEMs are classified according to their figures of merit (=1 / (2π x Ron x Coff)) and performance indicators like power handling, insertion loss, life cycle, switching speed and isolation. Various actuation mechanisms were compared, and electrostatic scheme was chosen because of the criticality of low power consumption in large-scaled systems. Previous work on RFMEMs was reviewed, and switching speed was selected as the focus of this project because of fewer works done in this aspect. Mechanical dynamics of RFMEMs such as stiffness, Young’s Modulus, poisson ratio and residual stress were examined. Failure mechanisms were scrutinized and fast-switching concepts were studied. Design was commenced based on a boat-like geometry for the RFMEMs bridge that boosts the spring constant and implemented in a co-planar wave electromagnetic configuration. The fabrication process which manipulates baking parameters to reflow and form the angled edges was described. Computation of capacitances and simulations of mechanical resonance and scattering parameters for each switch state were performed using various software programs and analysed. Due to glitches in mask fabrication and restrictions levied on EEE undergraduates regarding clean-room equipment usage, the switch has not yet been fabricated and thus measurement testing cannot be done. Based on results of mechanical and electromagnetic behaviour from simulation, the project goal of attaining faster switching speeds was achieved, whereas the scattering parameters indicated a low capacitance ratio. Therefore, it is preferable to use the switch as a varactor rather than a switch. But the geometry can be applied to metal-contact switches to improve the capacitance ratio.