Analysis and design of wideband monopole antennas

Abstract

Monopole antennas are the simplest and probably the most widely used antenna in wireless communication systems, especially at lower frequencies. However, conventional monopole antennas are restricted in bandwidth. Thus, broadening the limited bandwidth of conventional monopole antennas has long been an attractive research topic. This report presents the analysis and optimization design of a series of monopole variations by using the modal expansion analysis, method of moments and genetic algorithm. The objective of the research work is to explore monopole antennas with a wider input impedance band-width, with a relatively small size, and with a simple structure. The accurate and efficient modal-expansion method (MEM) is used to calculate the electromagnetic fields and in-put impedance of the rotational symmetric structures. The method of moments based Numerical Electromagnetics Code (NEC) is also applied in the simulation. The effective Emperor-Selective genetic algorithm (EMS-GA) is used for automatic optimization. The MEM, NEC and EMS-GA are discussed in detail. A few new monopole antenna models are proposed and studied in this thesis, including the top-cap monopole antenna, the ver-tically corrugated monopole antenna, the horizontally corrugated monopole antenna and a series of sleeve monopole antennas. Finally, the thesis discusses some possible future research work on the analysis and optimization design of broadband monopole antennas.