| Summary: | Since the release by the Federal Communications Commission (FCC) of a bandwidth of 7.5GHz (from 3.1GHz to 10.6GHz) for ultra wideband (UWB) wireless communications, UWB is rapidly advancing as a high data rate wireless communication technology. As is the case in conventional wireless communication systems, an antenna also plays a very crucial role in UWB systems. However, there are more challenges in designing a UWB antenna than a narrow band one. A suitable UWB antenna should be capable of operating over an ultra wide bandwidth as allocated by the FCC. At the same time, satisfactory radiation properties over the entire frequency range are also necessary. Another primary requirement of the UWB antenna is a good time domain performance, i. e. a good impulse response with minimal distortion. This thesis focuses on UWB antenna design and analysis. Studies have been undertaken covering the areas of UWB fundamentals and antenna theory. Extensive investigations were also carried out on two different types of UWB antennas. The first type of antenna studied in this thesis is circular disc monopole antenna. The vertical disc monopole originates from conventional straight wire monopole by replacing the wire element with a disc plate to enhance the operating bandwidth substantially. Based on the understanding of vertical disc monopole, two more compact versions featuring low-profile and compatibility to printed circuit board are proposed and studied. Both of them are printed circular disc monopoles, one fed by a micro-strip line, while the other fed by a co-planar waveguide (CPW). The second type of UWB antenna is elliptical/circular slot antenna, which can also be fed by either micro-strip line or CPW. The performances and characteristics of UWB disc monopole and elliptical/circular slot antenna are investigated in both frequency domain and time domain. The design parameters for achieving optimal operation of the antennas are also analyzed extensively in order to understand the antenna operations. It has been demonstrated numerically and experimentally that both types of antennas are suitable for UWB applications.
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