Ultra-wideband Antenna Research And Design

In recent years, with the rapid development of military and civilian communication technology, the UWB antenna has been developing toward the direction of miniature and wideband. Moreover, to avoid the interference resulting from frequency overlap between the UWB system and other systems, the UWB antenna with band-notched characteristics become research hotspots in antenna field. The printed monopole antennas have received considerable attention owing to their attractive merits, such as simple structure, ease of fabrication and properties of wideband. The dissertation will include the following contents:1. Firstly, this thesis introduces the fundamental structure of the planar monopole antenna and discusses its working principles. Then using the round corners and steps on radiating patch separately, two types of the improved monopole antenna fed by microstrip line are presented. The simulated results demonstrate that the two antennas achieve a ratio impedance bandwidth of 19:1. The slot antenna takes advantage of the two types of the improved measures above, and achieves a ratio impedance bandwidth of above 20:1. Then a hollowed monopole antenna fed by CPW feed line is presented, and the simulated results demonstrate that it exhibits a nearly omni-directional radiation pattern over its whole frequency band. Finally, a CPW-fed conformal monopole antenna with the similar radiating patch of the first improved planar antenna is proposed, and it achieves nearly a ratio impedance bandwidth of 20:1.2. In order to realize the miniaturization, a half CPW-fed UWB monopole antenna is proposed. Some improvements on antenna are introduced to further reduce the lowest frequency of operation, and a significant 40% reduction in size is realized. The simulated bandwidth ranges from 1.99GHz to more than 40GHz.3. In order to avoid the interference from overlapping of the frequency band with the WLAN system, the C-shaped slot into the monopole antenna is introduced. The effects of the different dimension and location of the slot are analyzed, and the proposed antenna has reached band-notched characteristics at certain frequency.