A dissertation submitted to the faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of science in Engineering Johannesburg 1991 / This dissertation discusses the interaction between shipboard antennas and their environment. The emphasis is on the Use of the Method of Moments to calculate the currents on the structure of the ship. These currents are induced by the antennas mounted on the structure of the ship. The parameters (such as grid spacing and wire radius) to use in creating a wire grid model of the ship is investigated and recommended values given. A sample ship is analyzed and the results obtained compared with measurements done in an unechoic chamber.

However, applying directional antennas to wireless networks can also cause new collisions, such as the new hidden terminal problem and the deafness problem. We study the challenges in the MAC layer design with directional antennas and present the state of the art of current MAC protocols with directional antennas. Then, we propose a novel collision avoidance scheme in terms of BT-DMAC (Busy-Tone based Directional Medium Access Control) to address the new collisions with directional antennas. Both the analytical and simulation results show that transmitting busy tones on a different channel can effectively reduce the hidden nodes and mitigate the deafness problem. Thus, integrating multiple channels with directional antennas can bring numerous benefits. Furthermore, we also explore some techniques in the MAC layer design with directional antennas. Some useful insights are also given. / The capacity of wireless networks are mainly affected by two key factors: the interference among concurrent transmissions and the number of simultaneous transmissions on a single interface. Recent studies have found that, using multiple channels can separate concurrent transmissions and significantly improve network throughput. However, those studies only consider wireless nodes that are only equipped with omni-directional antennas, which cause high collisions. On the other hand, some researchers have found that directional antennas bring more benefits such as the reduced interference and the increased spatial reuse compared with omni-directional antennas. But, they only focused on a single-channel network which only allows finite concurrent transmissions. In this thesis, we propose a novel network architecture, in terms of multi-channel networks using multiple directional antennas ( MC-MDA), which integrates the two technologies of multiple channels and directional antennas together and potentially brings more benefits. / We study the capacity of MC-MDA networks and explore the benefits of such networks. We have found that using directional antennas in multi-channel networks can greatly increase the network capacity. Furthermore, such networks require fewer channels than multi-channels with omni-directional antennas. More specifically, we study the channel assignment problem of such MC-MDA networks. Our results indicate that using directional antennas in wireless networks can significantly reduce the required number of channels. Directional antennas have a better spectrum reuse than omni-directional antennas. / Dai, Hongning. / Adviser: Kam-Wing Ng. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3596. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 173-183). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Yim, Ho Yan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 125-128). / Abstracts in English and Chinese. / Abstract --- p.ii / 論文摘要 --- p.iv / Acknowledgement --- p.vi / Table of Content --- p.vii / List of Figures --- p.x / List of Tables --- p.xiv / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Filter --- p.3 / Chapter 1.2 --- Antenna --- p.4 / Chapter 1.3 --- Outline of the Thesis --- p.6 / Chapter Chapter 2 --- Basic Theories in Filter and Patch Antenna Design --- p.7 / Chapter 2.1 --- Microwave Filter Design --- p.7 / Chapter 2.1.1 --- Transfer Functions --- p.8 / Chapter 2.1.2 --- Lowpass Prototype Filters and Elements --- p.14 / Chapter 2.1.3 --- Filter Transformations --- p.18 / Chapter 2.1.4 --- Admittance Inverter --- p.21 / Chapter 2.2 --- Antenna Concepts --- p.23 / Chapter 2.2.1 --- Microstrip Antenna --- p.23 / Chapter 2.2.2 --- Patch Antenna Design --- p.24 / Chapter 2.2.3 --- Polarization --- p.28 / Chapter Chapter 3 --- Review of Conventional Dual-band Filter Designs --- p.33 / Chapter 3.1 --- Bandstop / bandpass Filters in a Cascade Connection --- p.33 / Chapter 3.2 --- Stepped Impedance Resonator --- p.34 / Chapter 3.3 --- Tunable Transmission Zero for Spurious Responses Suppression --- p.36 / Chapter 3.4 --- Comparison --- p.38 / Chapter Chapter 4 --- Novel Dual-band Filter Design with Equal Bandwidth --- p.39 / Chapter 4.1 --- Introduction --- p.39 / Chapter 4.2 --- Frequency Behavior of Shunt Stubs --- p.39 / Chapter 4.3 --- Dual-band Resonator with Paralleled Stubs --- p.42 / Chapter 4.4 --- Dual-band Admittance Inverter --- p.47 / Chapter 4.5 --- Dual-band Filter Realization --- p.51 / Chapter 4.5.1 --- Simulation Examples --- p.54 / Chapter 4.5.2 --- Comparison of Simulation results --- p.60 / Chapter 4.5.3 --- Experimental Results --- p.64 / Chapter Chapter 5 --- Novel Dual-band Filter Design with Unequal Bandwidth --- p.70 / Chapter 5.1 --- Introduction --- p.70 / Chapter 5.2 --- Dual-band Resonator using Step-Impedance Line --- p.70 / Chapter 5.3 --- Dual-band Admittance Inverter --- p.74 / Chapter 5.4 --- Dual-band Filter Realization --- p.75 / Chapter 5.4.1 --- Comparison of Simulation Results --- p.81 / Chapter 5.4.2 --- Experimental Results --- p.85 / Chapter Chapter 6 --- Review of Conventional CP Antenna Designs --- p.91 / Chapter 6.1 --- Degenerated Mode Patch --- p.91 / Chapter 6.2 --- CP Stacked Microstrip Patch Antenna Array --- p.92 / Chapter 6.3 --- Coplanar Waveguide-fed Slot Antenna --- p.93 / Chapter 6.4 --- Dual-band CP antenna fed by 2 different 90° hybrid couplers --- p.95 / Chapter Chapter 7 --- Novel New Dual-band CP Antenna Design --- p.96 / Chapter 7.1 --- Introduction --- p.96 / Chapter 7.2 --- Dual-band CP Patch Antenna --- p.96 / Chapter 7.2.1 --- Slotted Square Patch Antenna --- p.96 / Chapter 7.2.2 --- Slotted Cross Patch Antenna --- p.99 / Chapter 7.2.3 --- Simulation Results: Slotted Cross Patch Antenna --- p.101 / Chapter 7.3 --- Dual-band Quadrature Hybrid --- p.104 / Chapter 7.3.1 --- Simulation Results: Dual-band Hybrid Coupler --- p.107 / Chapter 7.4 --- Dual-band CP Antenna Realization --- p.113 / Chapter 7.4.1 --- Antenna Configuration --- p.113 / Chapter 7.4.2 --- Measurement Setup --- p.114 / Chapter 7.4.3 --- Experimental Results --- p.115 / Chapter Chapter 8 --- Conclusions and Recommendations for Future Work --- p.123 / Chapter 8.1 --- Filter --- p.123 / Chapter 8.2 --- Antenna --- p.123 / Chapter 8.3 --- Recommendations for future work --- p.124 / References --- p.125 / Author's Publications --- p.128 / Acronyms and Abbreviations --- p.129

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 153-156).

The explosive growth of the biosensors and health-related wearable monitoring devices has accentuated the need for miniaturized, high-efficiency conformal bio-modules that can operate over a wide range of frequencies, while they can be integrated in wearable and lightweight configurations. One of the major issue for the implementation of Wireless Body Area Networks (WBAN) is the very limited range of commonly used metal antennas. Due to the high dielectric constant between the metal antenna material (as well as the metal-based circuitry) and the mostly "ionized-water" human body parts, the near-field gets significantly disturbed, while local reflections due to the dielectric mismatch further shorten the operation range. Even wearable bracelet-like sensing devices have a very low range due to this reason. Thus, there are two major aspects that are going to be addressed in this Thesis: enhanced-range wearable antennas for wireless biosensors and compact "rugged-polarization" wireless sensor readers.

Thesis (Ph. D.)--University of Queensland, 2001. / Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 68-72). Also available in electronic version. Access restricted to campus users.

Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, March 2003. / Thesis advisor(s): Tri T. Ha, Jovan Lebaric. Includes bibliographical references (p. 77-78). Also available online.

Wireless communication continues to make a profound impact upon our daily lives. The oft-touted benefits of high data rates and improved reliability via wireless communication are limited by its inherent drawbacks, including path loss, fading and interference. One promising strategy for overcoming these problems is to deploy nodes in the region between a transmitter and its intended receiver. These intermediate nodes can improve communication for this transmitter-receiver pair by receiving a transmitted message, processing it and relaying the processed output to the receiver. This transmission strategy, known as relay-assisted communication, can be especially beneficial when the transmitter-receiver pair are either separated by a large distance or when a large obstruction blocks the path between them. In a reasonably dense network, several relays may be available to assist a particular transmitter-receiver pair. Deciding which relays should forward the transmitted message is actually quite difficult. For example, the relay with the best physical-layer channel gain to the destination may also be running low on battery power. Another relay may have a good physical-layer channel gain to the destination and a reasonable amount of remaining battery power, but its queue may be full of messages from other transmitters, so it cannot forward a newly arrived message within a given delay constraint. Thus, optimal relay selection entails carefully balancing all system parameters, which is prohibitively complex in current wireless systems. This dissertation provides novel results for dealing with the relay selection problem in two distinct types of wireless systems. First, several selection algorithms are designed for single-antenna wireless networks, including a decentralized random access-based strategy and centralized methods that are based on throughput maximization and downlink user scheduling. Second, selection algorithms based on transmission hop length are designed for multipleantenna wireless networks. The presented strategies for both single-antenna and multiple-antenna relaying are highly intuitive, as they allow for concise descriptions, making them amenable to practical implementation. Also, the presented strategies illustrate the importance of application-specific design, since each of them yields good performance by focusing on a small set of system parameters. For example, observed latency is of paramount importance for wireless networks that support a significant level of video traffic. / text