Thesis (M.S.)--Oregon State University, 2004. / Printout. Includes bibliographical references (leaves 47-50). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2004. / Printout. Includes bibliographical references (leaves 41-43). Also available on the World Wide Web.

Thesis (M.S.)--Rutgers University, 2008. / "Graduate Program in Electrical and Computer Engineering." Includes bibliographical references (p. 63-66).

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2005. / Includes bibliographical references (leaves 62-65). Also available in electronic version.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 191-196).

Antennas design procedure, especially in portable devices, has been influenced by the growing demand for development of modern wireless communications. Hence, antennas that are wideband, compact, low profile, low cost, and easy to integrate into printed circuits are required. The research described in this dissertation focuses on optimally design and analysis of compact, low profile, and planar wideband patch antennas for modern wireless communications, namely, an open slot wideband planar antenna, a dielectric loaded wideband antenna, a planar antenna with ultra-wideband performance, and an E-shaped patch antenna. A novel very compact planar antenna with wideband performance is proposed and investigated. The proposed antenna has a size of only 9.2 mm x 9.8 mm x 1.52 mm. The size miniaturization is achieved by inserting an open slot in the ground plane to reduce the phase velocity. The antenna has achieved an impedance bandwidth of 52.16% and a stable radiation patterns over a wider bandwidth with a size reduction about 88%. Optimization of a dielectric loaded antenna by using Covariance Matrix Adaptation Evolutionary Strategy (CMA-ES) technique to achieve wideband and ii symmetrical broadside radiation performance is presented. Simulation is used to investigate the frequency-domain performance, regarding return loss, gain, and radiation pattern. Experimental measurements have also been performed to validate the performance of the proposed antenna. The obtained results show that the proposed dielectric loaded antenna achieves a good impedance matching and radiation characteristics in the entire band of WLAN IEEE 802.11a. A new ultra-wideband low profile microstrip antenna is presented for wireless applications. The proposed antenna has a compact size of 20x16 mm2 and an impedance bandwidth of 134.88% (3.5 GHz to 18 GHz). With the compact, ultra-wideband, and low profile, the proposed antenna can be a very good candidate for a wide range of communication applications. Spider Monkey Optimization (SMO) method is introduced for the first time for solving electromagnetic problems. The SMO is a new swarm intelligence technique which models the foraging behavior of spider monkeys. To show the efficiency of the SMO, different examples are presented and the results are compared with the results obtained using other popular optimization techniques. The optimization procedure is used to synthesis the array factor of a linear antenna array and to optimally design a rectangular and an E-shaped patch antenna for wireless applications. By comparing to traditional optimization techniques that reported in the literature, it is evident that SMO is efficient in reaching the optimum solutions with less number of experiments. The performance results obtained from study of these antennas show that these antennas can be an excellent choice for a wide range of wireless communication applications.

This master thesis is as a final project in the Division of Computer Engineering at the Department of Electrical Engineering, Linköpings University, Sweden. The purpose of the project is to design a wide frequency range programmable frequency divider used in a PLL circuit for ultra wide band system. 0.18 um tsmc CMOS technology is used in this project. A brief introduction of PLL circuits and UWB specifications are given in the report and the circuit design issue is presented. Post-layout simulation results are shown in the later part of the report. The focus of this project is to make the frequency divider work well in wide range and high speed. Therefore, how to shorten feedback circuits’ latency and how to reduce complexity of the circuits are the main problems. Logic gate merged technique is used to reduce transistor number and carefully drawing layout makes the circuit work well in post-layout simulation.

The principal contributions of this study include the development of a new capacitive feeding mechanism for wideband probe-fed microstrip patch antennas as well as the implementation of a spectral-domain moment-method formulation for the efficient analysis of large, but finite arrays of these elements. Such antenna configurations are very useful in the wireless communications industry, but extremely difficult to analyse with commercially available software. Probe-fed microstrip patch antennas have always been a popular candidate for a variety of antenna systems. Due to their many salient features, they are well suited for modern wireless communication systems. However, these systems often require antennas with wideband properties, while an inherent limitation of probe-fed microstrip patch antennas is its narrow impedance bandwidth. This can be overcome by manufacturing the antenna on a thick low-loss substrate, but at the same time it also complicates things by rendering the input impedance of the antenna very inductive. In this thesis, a new capacitive feeding mechanism is introduced that can be used for probe-fed microstrip patch antennas on thick substrates. It consists of a small probe-fed capacitor patch that is situated next to the resonant patch. The benefits of this configuration include the fact that only one substrate layer is required to support the antenna. It is also very easy to design and optimise. The use of full-wave methods for an accurate analysis of microstrip antennas, has basically become standard practice. These methods can become very demanding in terms of computational resources, especially when large antenna arrays have to be analysed. As such, this thesis includes a spectral-domain moment-method formulation, which was developed for the analysis of probe-fed microstrip patch antennas or antenna arrays that comprise of the new capacitive feeding mechanism. Here, entire-domain and subdomain basis functions are combined in a unique way so as to minimise the computational requirements, most notably computer memory. It is shown that, for general antenna array configurations, memory savings of more than 2500 times can be achieved when compared with typical commercial software packages where only subdomain basis functions are used. Some of the numerical complexities that are dealt with, include various methods to evaluate the spectral integrals as well as special algorithms to eliminate the recalculation of duplicate interactions. The thesis also contains a quantitative comparison of various attachment modes that are often used in the moment-method modelling of probe-to-patch transitions. Various numerical and experimental results are included in order to verify the spectral-domain moment-method formulation, to characterise the new feeding mechanism and to illustrate its use for various applications. These results show that, in terms of accuracy, the spectral-domain moment-method formulation compares well with commercial codes, while by comparison, it demands very little computer memory. The characterisation results show that the input impedance of the antenna can be fully controlled by only adjusting the size of the capacitor patch as well as the width of the gap between the capacitor patch and the resonant patch. In terms of applications, it is shown how the new antenna element can effectively be employed in linear arrays with vertical polarisation, horizontal polarisation or dual slant-polarisation. These represent some widely-used configurations for modern base-station antennas. / Thesis (PhD (Electronic Engineering))--University of Pretoria, 2005. / Electrical, Electronic and Computer Engineering / unrestricted

In recent years, ultra-wideband (UWB) communications has gained tremendous popularity in both research community and industry. The large bandwidth of UWB systems raises new wireless channel effects and consequently unique advantages as well as challenges to be dealt with, compared to conventional wireless systems. One of these advantages is the ability to resolve dense multipath components and use Rake combining at the receiver in order to significantly reduce the negative effects of fading. However, implementing a Rake receiver with a sufficiently large number of fingers to make use of this advantage is an evident challenge for most UWB devices with limited signal processing capabilities. A possible approach to overcome this problem is to move computational complexity from the receiver to the more powerful transmitter, which is the main focus of the present work. In this thesis, we propose two novel pre-equalization schemes for multiple- input single-output (MISO) direct-sequence ultra-wideband (DS-UWB) systems with pre-Rake combining and symbol-by-symbol detection. The first pre-equalization filter (PEF) scheme employs one PEF per transmit antenna, whereas in the second, simplified PEF (S-PEF) scheme all transmit antennas share the same PEF. For both schemes the optimum finite impulse response (FIR) and infinite impulse response (IIR) PEFs are calculated based on the minimum mean squared error (MMSE) criterion. We show that in contrast to previously proposed schemes for DS-UWB, both our proposed PEF schemes efficiently exploit the channel shortening properties of the pre-Rake filter. In particular, our proposed PEF schemes operate at the symbol level. We also show that under certain conditions the S-PEF scheme achieves the same performance as the more complex PEF scheme. Finally, we demonstrate that a single-input multiple-output (SIMO) DS-UWB system with post-Rake combining and MMSE post-equalization is the dual system to the considered MISO DS–UWB system with pre-Rake combining and MMSE pre-equalization. This uplink-downlink duality can be exploited for efficient calculation of the PEFs and for complexity reduction. Our simulation results show that the proposed PEF schemes achieve significant performance gains over pre-Rake combining without equalization even if only short PEFs are employed, and this is the case even for long UWB channel impulse responses. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate