As sources of energy are becoming more scarce and expensive, energy harvesting is receiving more global interest and is currently a growing field. Energy harvesting is the process of converting ambient energy, such as vibration, to electrical energy that can power a multitude of applications. Vibration energy is the by-product of everyday life; it is generated from any perceivable activity. While typically viewed as noise, there is a strong potential for harvesting this energy and deploying it to useful applications. The focus of this thesis will be using vibration as the ambient source of energy. Hybrid energy harvesters employ more than one of the harvesting technologies. In this thesis, two hybrid harvesters that utilize piezoelectric, magnetostrictive, and electromagnetic technologies are designed, modelled, and tested. Both of these harvesters have beams that are spiral in shape. The use of the spiral geometry allows the system to have a lower natural frequency as opposed to the traditional cantilever beam, while still maintaining a high volume of active material. The first harvester that is discussed is the P-MSM harvester. It utilizes piezoelectric and magnetostrictive material. Both materials are configured in a spiral beam geometry and allowed to resonate independently. The resonance frequency of these two materials is designed to create wideband energy harvesting. This allows the harvester to be operating efficiently even if the ambient vibration shifts a small amount. The second harvester that is discussed is the P-MAG harvester. It utilizes piezoelectric and electromagnetic technologies. It also incorporates a spiral geometry for the piezoelectric layers and includes a magnet attached at the centre. The magnet is placed in the centre of the spiral to reduce the natural frequency of the system and to also actively contribute to the harvesting. This harvester has two sources operating at the same resonant frequency, which allows it to have a larger power output than if the sources were separated. Finally, finite element analysis was used to model both harvesters. ANSYS was used for the piezoelectric material and COMSOL was used for the electromagnetic material. The results are compared to the experimental and are in good agreement.

Ultra wideband (UWB) systems have the potential for high data rate applications such as high-definition video streaming, high speed data transfer, etc. Recently, WiMedia based UWB evaluation systems and commercial products are available from industry. In order to understand the true performance of the WiMedia UWB system, it is important to study its characteristics from mathematical models and practical measurement tests. One of the key objectives of this thesis is to determine the important parameters in the path loss model based on the measurement results from the intended environments. Our focus is on residential environments including office buildings and houses, where intensive measurements are performed from various layers of a network (e.g. physical layer, packet level and application level). The results show that the WiMedia UWB system is fully capable of handling different high rate applications in residential networks. Another goal of this thesis is to propose a medium access control (MAC) protocol design tailored to high rate residential UWB wireless networks. The proposed multiband distributed MAC design utilizes the unique capabilities of UWB technology and the environment characteristics. We elaborate the design details and build a discrete event simulation program for performance evaluation purpose. By evaluating from both theoretical analysis and simulation, we show that the proposed MAC design has substantial advantage over single channel MAC in a high rate residential UWB wireless network. / Graduate

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An ultra-wideband (UWB) spatial filter is proposed to mitigate multipath effects in a one-way, one-dimensional time-of-arrival (TOA) localization system for use inside a tunnel. The spatial filter is a weighted array of judiciously placed antennas and it exploits the fact that electromagnetic waves propagate as modes in a tunnel by selectively extracting these mode(s). The design of several spatial filters is presented alongside vigorous analyses to characterize the localization performance afforded by them in a noisy environment. The filters are evaluated using data from an analytical equation waveguide model, a ray tracer model and measurements. These spatial filters deliver accurate localization estimates across distance and well-designed filters can operate at higher SNRs and further distances than single sensors. Insights into successful spatial filter design are provided and this spatial filtering technique has created a new branch of multipath-aware localization systems.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references (p. 51-53 ). Also available in electronic version.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (Ph.D.)--University of Central Florida, 2008. / Adviser: Lei Wei. Includes bibliographical references (p. 113-119).

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (Ph.D.)--Tennessee Technological University, 2008. / Bibliography: leaves 106-112.

Thesis (Ph.D.)--Tennessee Technological University, 2008. / Includes bibliographical references.