Thesis (M.S.)--Ohio University, August, 1998. / Title from PDF t.p.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 226-230). Also available via the Internet.

Thesis (Ph.D.)--Syracuse University, 2008. / "Publication number: AAT 3333567."

The primary focus of this dissertation is on the analyses of self-resonant bent antennas. The need for the accurate characterization of such antennas due to their growing importance in present day wireless communications is the motivation for this work. To this end, several self-resonant bent antennas are analyzed which includes an inverted-L antenna (ILA), a meander-line dipole (MLD) antenna, a meander-line bow-tie (MLBT) antenna, a dual meander antenna, and a printed meander antenna. A simple analytical model, based on the induced EMF method, is presented to compute the input impedance of the ILA. First, a sinusoidal distribution of current on the antenna, with zero current at the end is assumed, and then an expression for the input impedance is derived using the near-fields of the antenna. The accuracy of the formulation is verified by comparing the results computed using it with that from NEC [1] computation. Unlike the analytical solutions available in the literature, our proposed solution is not restricted to antennas that are electrically small. In addition the new formulation can be extended to treat other antennas, such as the T-antenna, the folded unipole antenna, and the loop-loaded monopole antenna. The input impedance, radiation pattern, and gain of the MLD and MLBT antennas are computed and correlated with their parameters. Input impedances of both antennas are computed using NEC. Simple analytical models are presented to compute the radiation patterns of the MLD and the MLBT antennas. For each antenna, a sinusoidal distribution of current is assumed and closed-form expressions for the radiation fields are derived. The results computed using the analytical models are verified by comparing them with the results from the NEC computation. Since in each model the radiation pattern of an antenna is expressed in terms of ready to evaluate algebraic expressions, the computation of such pattern is fast and easy. The input impedance and radiation characteristics of a dual meander antenna are computed using NEC. Similarly as before the input impedance, radiation pattern, and gain of this antenna are also correlated with its parameters. The input impedance and radiation pattern of a planar printed meander antenna are investigated using the Finite-Difference Time-Domain (FDTD) technique. The antenna is modeled on a dielectric substrate both in the presence and absence of a metallic ground plane. Characteristics of the antenna are examined as function of dielectric constant, and substrate thickness. New results of input impedance, radiation pattern, and gain are presented which are vital for the design of such antennas. Several novel applications of self-resonant bent antennas are described. First, a wide-band dual meander-sleeve antenna is designed, manufactured, and measured for application in dual frequency vehicular personal communication. The antenna can operate simultaneously in the 824-894 MHz and 1850-1990 MHz bands of the PCS system. Second, an MLBT dipole is introduced as a feed for plane sheet reflectors. Numerical results computed using NEC show that the feed when used in front of a plane sheet reflector, results in superior radiation characteristics than a conventional dipole feed, namely, it reduces the reflector dimension by 46% for the same front to back ratio, beam width and gain. Finally, a compact plane sheet reflector antenna is described that uses an MLBT monopole feed. Since the antenna uses a monopole, a balun is not required. This antenna has a gain and half-power beam width of 8.4 dBi and 94° respectively. / Graduate

A thesis submitted to the Faculty of Engineering,University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree or Doctor of Philosophy. / The aim of the thesis is to develop techniques for the analysis of antennas composed of dipoles and folded dipoles,that are efficient relative to the method-of-moments. (Abbreviation abstract) / AC2017

Wireless communication is part of our daily life in several applications, such as cell phones, wireless printers, sensors, etc. Each wireless device requires at least one antenna to communicate with other devices. In 2002, Federal Communications Commission (FCC) assigned a frequency spectrum from 3.1 GHz to 10.6 GHz for ultra-wideband communications. Several narrowband antennas require to cover the entire range. Unlike narrowband antennas, ultra-wideband antennas need to cover the wide frequency band. This research mainly focuses on physically small antenna designs. The first antenna discussed in this dissertation is a dual, triple trident antenna with dimensions 24 mm × 28 mm × 0.785 mm, which will operate from 3 GHz to 12.15 GHz [58]. The first antenna consists of six tridents symmetrical along the vertical direction. The second antenna design is a novel rectangular ring ultra-wideband antenna [59]. Large antennas operate for low frequency, and small antennas work for high frequency. The number of rings increased in wideband antenna to 9 from 4 to check the design methodology. The rectangular ring ultra-wideband antenna has dimensions 24 mm × 26 mm × 1.52 mm. This antenna operates from 3.12 GHz to 12.85 GHz. The third antenna design is an ultra-wideband dual square trident planar antenna. This antenna’s overall size is 26 mm × 24 mm × 1.56 mm [60]. This antenna has impedance bandwidth from 3.65 GHz to 12.50 GHz. The fourth antenna design is an ultra-wideband antenna with a band notch from 5.05 GHz to 5.9 GHz [61]. This antenna consists of two tridents and two split-ring resonators along the microstrip feed line. The overall size of this antenna 26 mm ×24 mm × 1.53mm. Simulations are carried out using the CST microwave studios® to analyze the antenna performance. Experiments are conducted to verify the simulated results using vector network analyzers for impedance and anechoic antenna chamber for radiation characteristics of the antenna. All four antennas are excellent for the wireless device due to their compact size and planar designs.

The wireless network design problem (WNDP) considers how best to place a set of antennas so the antennas can send and receive the maximum possible amount of data subject to network-performance constraints (e.g., channel-availability constraints). To date, little research has considered how to choose the network-antenna layout that maximizes throughput under these conditions. Also, past research has mainly investigated networks with omnidirectional antennas only, not other types of antennas. A bi-level mixed-integer program is constructed to solve this problem using a cutting-plane approach. The data produced from this model demonstrate an extension of the WNDP under more realistic conditions than have been simulated previously. The questions answered by this research are as follows: (1) what are the effects on network throughput of utilizing directional or sectored antennas instead of omnidirectional antennas, and (2) what is the maximum possible throughput when imposing constraints related to differing interference types and channel availability?

No description available.

yes / A compact dual U-shaped slot PIFA antenna with Electromagnetic Bandgap (EBG) material on a relatively low dielectric constant substrate is presented. Periodic structures have found to reduce mutual coupling and decrease the separation of antenna and ground plane. A design with EGB material suitable for a small terminal mobile handset operating at 2.4 GHz was studied. Simulated and measured scattering parameters are compared for U-shaped slot PIFA antenna with and without EBG structures. An evaluation of MIMO antennas is presented, with analysis of the mutual coupling, correlation coefficient, total active reflection coefficient (TARC), channel capacity and capacity loss. The proposed antenna meets the requirements for practical application within a mobile handset. / Electronics and Telecommunications

Millimeter waves, corresponding to the frequency range 30 to 300 GHz, have characteristics which make them ideal for many applications. Antennas at these frequencies have the advantage of reduced size and weight and can be fabricated as an integral part of the system they are used in. Millimeter wave microstrip antennas have been extensively researched over the past decade. The purposed of this report was to build and test 35 GHz microstrip antennas as well as put into operation a high voltage klystron power supply, Micro-Now Model 756. The antennas were fabricated and tested in the lab and the results obtained are reported. The operation of the Model 756 power supply is also outlined in detail.