No description available.

A frequency selective surface (FSS) based on switchable slots in the ground plane is presented. The switching is done using an actuating MEMS bridge over the slot. The intent is to demonstrate the control of the resonance frequency of the FSS by deflecting the bridge. It is shown that by applying a voltage between the bridge and the ground plane, the bridge displaces and changes the system capacitance which in turn changes the resonance frequency. Two analyses are presented; (1) Electromechanical analysis to show how the bridge deflects by the voltage, (2) Electromagnetic analysis to show how the resonance frequency changes by the bridge deflection. The device was fabricated and tested. The measurement results are presented for two up and down positions of the MEMS bridge to verify the correctness of the theory and design.

No description available.

The design of emergent wireless sensor networks operating near the ground requires channel models that account for previously unconsidered propagation phenomena. Most models used for link planning and radio design of the last century were designed for use in situations where the transmitters were at least tens of meters above the earth surface. However, near the earth surface, the specifics of the ground composition and atmospheric effects have been postulated to play a significant role. This dissertation describes the first set of investigations in this emergent environment. A novel computational electromagnetics model is presented that can calculate electromagnetic fields of a dipole embedded in planar-stratified propagation medium that represents the ground and near-surface atmosphere. It is the first available electromagnetic model to efficiently combine a spectral-domain solution in arbitrary multilayers of lossy-dielectric media with high-order quadrature routines to synthesize the fields of an impressed dipole. For the first time, high-order asymptotic quadrature is used to efficiently obtain solutions at arbitrary ranges from the dipole source. A measurements-based model of the near-ground atmosphere is derived, and results of modeling the atmosphere are used to predict the performance of an ultra-high-frequency radio system operating near the ground surface. Finally, a study is conducted to determine the effects of varying key parameters in the near ground channel, including atmospheric conditions, ground conditions, and frequency. The primary result is that ultra-high-frequency near-earth narrowband channels are largely insensitive to large-scale refractive effects that occur naturally on Earth; however, as the transmitter frequency increases into the super-high-frequency and millimeter wave regimes, refractive effects have significant effects on the radio propagation environment.

xii, 186 leaves : ill., graphs, tables ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.1979) from the Dept. of Electrical Engineering, University of Adelaide

Thesis (M.S.)--University of Texas at Dallas, 2007. / Includes vita. Includes bibliographical references (leaves 84-85)

Thesis (Ph. D.)--University of Hong Kong, 2008. / Includes bibliographical references (leaf 87-98) Also available in print.

Thesis (Ph.D.)--University of Texas at Dallas, 2008. / Includes vita. Includes bibliographical references (leaves 93-98)

Thesis (M.S.)--Rochester Institute of Technology, 1991. / Typescript. Includes bibliographical references (leaves 59-60).

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 92-93). Also available via the Internet.