2026-09-21T23:12:11Zhttps://bura.brunel.ac.uk/oai/request

oai:bura.brunel.ac.uk:2438/59272014-11-01T12:50:59Zcom_2438_23com_2438_58com_2438_8621com_2438_8620col_2438_3672col_2438_186col_2438_8623

Nilavalan, R Spasos, Michail N 2011-10-24T15:44:27Z 2011-10-24T15:44:27Z 2011 http://bura.brunel.ac.uk/handle/2438/5927 This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University. Reconfigurable antennas are attractive for many military and commercial applications where it is required to have a single antenna that can be dynamically reconfigured to transmit or receive on multiple frequency bands and patterns. RF-MEMS is a promising technology that has the potential to revolutionize RF and microwave system implementation for next generation telecommunication applications. Despite the efforts of top industrial and academic labs, commercialization of RFMEMS switches has lagged expectations. These problems are connected with switch design (high actuation voltage, low restoring force, low power handling), packaging (contamination layers) and actuation control (high impact force, wear, fatique). This Thesis focuses on the design and control of a novel ohmic RF-MEMS switch specified for reconfigurable antennas applications. This new switch design focuses on the failure mechanisms restriction, the simplicity in fabrication, the power handling and consumption, as well as controllability. Finally, significant attention has been paid in the switch’s electromagnetic characteristics. Efficient switch control implies increased reliability. Towards this target three novel control modes are presented. 1) Optimization of a tailored pulse under Taguchi’s statistical method, which produces promising results but is also sensitive to fabrication tolerances. 2) Quantification of resistive damping control mode, which produces better results only during the pull-down phase of the switch while it is possible to be implemented successfully in very stiff devices. 3) The “Hybrid” control mode, which includes both aforementioned techniques, offering outstanding switching control, as well as immunity to fabrication tolerances, allowing an ensemble of switches rendering an antenna reconfigurable, to be used. Another issue that has been addressed throughout this work is the design and optimization of a reconfigurable, in pattern and frequency, three element Yagi-Uda antenna. The optimization of the antenna’s dimensions has been accomplished through the implementation of a novel technique based on Taguchi’s method, capable of systematically searching wider areas, named as “Grid-Taguchi” method. Submitted by Lesh Gowreesunker (lesh.gowreesunker@brunel.ac.uk) on 2011-10-24T15:44:04Z No. of bitstreams: 1 Fulltext.pdf: 3602946 bytes, checksum: 2bb9f3b18c9297552823ae006a353258 (MD5) Approved for entry into archive by Lesh Gowreesunker(lesh.gowreesunker@brunel.ac.uk) on 2011-10-24T15:44:27Z (GMT) No. of bitstreams: 1 Fulltext.pdf: 3602946 bytes, checksum: 2bb9f3b18c9297552823ae006a353258 (MD5) Made available in DSpace on 2011-10-24T15:44:27Z (GMT). No. of bitstreams: 1 Fulltext.pdf: 3602946 bytes, checksum: 2bb9f3b18c9297552823ae006a353258 (MD5) en Brunel University School of Engineering and Design PhD Theses http://bura.brunel.ac.uk/bitstream/2438/5927/1/FulltextThesis.pdf Hammerhead switch Taguchi optimisation technique Resistive damping Hybrid control Grid Taguchi RF-MEMS switches for reconfigurable antennas Thesis