The Study Of Ultra Wide Band Antennas

Ultra-Wide Band (UWB) is finding wide application in many areas, including wireless communication, microwave imaging, electronic countermeasure and so on, owing to its advantages such as high transmission rate, reasonable image resolution and good security. UWB antenna, affecting the performance of the whole system significantly, is considered to be one of the key components of UWB communication system.At first, UWB communication system and the development of UWB antennas are related briefly in this paper. Then, several kinds of traditional UWB antennas are introduced. Next, the methods of analyzing microstrip antenna, that is transmission line model theory, cavity model theory and full wave, are recommended. Finally, two compact UWB antennas with simple construction, which operate covering the band 3.1-10.6GHz and have dual band-notched function in the WLAN 5.2-5.8GHz band and ITU 8.025-8.4GHz band, are presented by applying several methods of broadening bandwidth, basing on theoretical analysis and considering the request of UWB system.Based on the stripline slot antenna shown in a reference, the UWB antenna with novel patch has a U-shaped structure between feed line and rectangle patch for ultra wide impedance matching. Two lying L-shaped splits in the patch are applied to obtain dual band-notched function. Compared with referred one, the proposed antenna reduced 31.1% in size, keeps the fractional bandwidth invariant and realizes dual band-notched function. Improved on the microstrip antenna with partial ground plane, the UWB antenna with novel ground plane realizes ultra wide impedance matching by adding balanced stubs in ground plane. Two concentric ring splits with gap are etched in the patch to obtain dual band-notched function. During the antenna design process, the influence of various structure parameters on antenna performance is discussed and analyzed. Both the proposed antennas are very good in property observing the simulated results. The UWB antenna with novel ground plane is constructed, and the measured results are in good agreement with the simulated ones.