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Abstract
Wire antennas are of spread use in the HF, VHF and UHF frequency ranges. They are most widely used antennas for wireless mobile communication systems. Arrays of dipoles, the famous form of the wire antennas, are commonly used as base-station antennas in mobile systems. They have attractive features such as simple construction, relatively broadband characteristics and small dimensions at high frequencies. Also loop antenna, a form of wire antennas, feature simplicity, low cost, versatility and have various shapes e.g. circular, triangular, square, elliptical, eh.
This thesis focuses on the analysis of wire antennas. The method of moments (MoM) is used to solve for the currents on these antennas. The thin wire approximation is used throughout the analysis.. Commercial software based on the MoM (NEC-win Professional) is used to obtain the numerical results and evaluation.
Chapter I of this thesis discusses the background theory of straight wire antennas. The electric field integral equation is derived and the MoM is then used to convert the integral equation into a system of linear equations which can be solved by various techniques.
Chapter 2 discusses and presents several resonant wire antennas such as, thin wire antenna, monopole antenna, folded dipole, Yagi-Uda antenna and the loop antenna in addition to broadband antennas: helical and traveling-wave wire antennas.
Chapter 3 presents a new wire antenna namely Ladder antenna. The radiation characteristics with and without infinite grounded plane are investigated. The change of the dimensions of this antenna and their affects on the radiation characteristics are obtained.
Chapters 4 and 5 also present another wire antenna namely the Figure-Eight and Double-Sided Isosceles Triangular antenna. The field patterns and gains in the principal planes over a range of frequencies are obtained for these antennas.