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Approved for public release; distribution is unlimited / This thesis addresses the prototyping, measurement, and validation of two circularly polarized microstrip patch antennas designed by LTJG Mahmut Erel for the NPSAT-1. The antenna system (receive and transmit), consisting of two antennas on a ground plane and their feed systems, was field-tested. The results were compared to the CSTʼ Microwave Studio. Finite Difference Time Domain (FDTD) software package predictions in order to verify that this design satisfies the NPSAT-1 requirements for bandwidth, free-space radiation pattern and low-profile shape. / Lieutenant Junior Grade, Turkish Navy

Research on multiple antenna systems has been a hot topic in recent years due to the demands for higher transmission rate and more reliable link in rich scattering environment in wireless communications. Using multiple antennas at both the transmitter side and the receiver side increases the channel capacity without additional frequency spectrum and transmitted power. However, due to the limited space at the size-limited terminal devices, the most critical problem in designing multiple antennas is the severe mutual coupling among them. The aim of this thesis is to provide compact, decoupled and efficient multiple antenna designs for terminal devices. At the same time, we propose a simple and cost effective method in multiple antenna measurement. All these efforts contribute to the development of terminal devices for the fourth generation wireless communication. The background and theory of multiple antenna systems are introduced first, in which three operating schemes of multiple antenna systems are discussed. Critical factors influencing the performance of multiple antenna systems are also analyzed in details. To design efficient multiple antenna systems in compact terminals, several decoupling methods, including defected ground plane, current localization, orthogonal polarization and decoupling networks, are proposed. The working mechanism and design procedure of each method are introduced, and their effectiveness is compared. Those methods can be applied to most of the terminal antennas, reducing the mutual coupling by at least 6dB. In some special cases, especially for low frequency bands below 1GHz, the chassis of the device itself radiates like an antenna, which complicates the antenna decoupling. Thus, we extend the general decoupling methods to the cases when the chassis is excited. Based on the characteristic mode analysis, three different solutions are provided, i.e., optimizing antenna locations, localizing antenna currents and creating orthogonal modes. These methods are applied to mobile phones, providing a more reliable link and a higher transmission rate, which are evaluated by diversity gain and channel capacity, respectively. In order to measure the performance of multiple antenna systems, it is necessary to obtain the correlation coefficients. However, the traditional measurement technique, which requires the phase and polarization information of the radiation patterns, is very expensive and time consuming. In this thesis, a more practical and convenient method is proposed. Fairly good accuracy is achieved when it is applied to various kinds of antennas. To design a compact and efficient multiple antenna system, besides the reduction of mutual coupling, the performance of each single antenna is also important. The techniques for antenna reconfiguration are demonstrated. Frequency and pattern reconfigurable antennas are constructed, providing more flexibility to multiple antenna systems. / QC 20120604

For laptop computers, the conventional internal antennas are usually used to operate in the WLAN system only, which can not provide sufficient and seamless services for wireless users. In order to overcome this problem, we propose some internal antennas having dual-/multi-network operation capability in this dissertation. Firstly, we present a combo antenna, which combines two shorted monopole antennas for operating in the WWAN/WLAN dual-network system. Secondly, we introduce a shorted monopole antenna through adding a parasitic element to enhance the impedance bandwidth for operating in the WLAN/WiMAX dual-network system. Thirdly, for achieving the compact-size antenna, we present a composite antenna which is composed of a ceramic chip and a printed radiating portion. Fourthly, we introduce a wideband shorted monopole antenna which can provide a wide bandwidth to cover the WPAN, WLAN, and WiMAX operations, and apply it to the MIMO system. Finally, we propose a coupling-type monopole antenna having multi-network operation capability and a compact size, which is about the smallest antenna for wideband operation in the laptop computer so far.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

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One of the fundamental properties of an antenna is its ability to radiate or receive more energy in one given direction over all the others. This property is called the directivity. The optimization of the directivity usually requires a great deal of attention when an antenna is being designed. There are a number of iterative analytical and experimental procedures available for the optimization of the directivity, however they can be manually intensive, and very time consuming when computer simulation is employed. / Optimization of antenna parameters has been hindered by the need of techniques that prove to be reliable, robust and can search and find a global maximum. Past efforts have focused on techniques confined to small search volumes due to the time overheads of searching. With the increasing utility of the personal computer, techniques have emerged which can search large volumes efficiently and economically. Genetic Algorithms are one such technique. / Genetic Algorithms are an optimization technique based on the mechanics of natural selection, which combines the biological concepts of survival of the fittest among string structures. They operate on a population of candidate solutions and are able to change a number of parameters simultaneously while testing the solutions for goodness-of-fit. They also possess memory so that a good solution can be saved and tested from generation to generation. In this way they are able to quickly find and maintain the best solution to the problem. / A Genetic Algorithm is used to optimize the directivity of a linear array of dipole radiators. Mutual and self-coupling is taken into consideration through the use of the Method of Moments. The inter-element spacing as well as the radiator length are allowed to vary. This gives the optimization many degrees of freedom. The arrays so optimized are verified using a standard industrial antenna software simulation program. The optimized array achieves a directivity of approximately 1.5 dB better than published data for a uniform array of the same size. There is an overall reduction in the length of the array of one wavelength and the currents on the radiating elements are realisable. The final product is a basic computer aided design package capable of optimizing the directivity of a linear antenna array with the only inputs needed being the frequency of operation and the number of dipole elements. / Thesis (MEng(ElectronicsEngineering))--University of South Australia, 2005.