| UWB(Ultra-wideband technology), as a short-range wireless communications, has abstracted increasing attention. UWB with advantages of high data-rate, good secrecy, low power consumption, good ability to resistance to multipath fading and penetration ability, low system cost and complexity. It has got a very big development in military communications, vehicle radar, digital communication and other fields. As an essential part of the UWB system, the UWB antenna has been drawn heavy attention in recent years. Its characteristics greatly influence the quality of communication system. However, the bandwidth (3.1-10.6GHz) of UWB antenna has covered other system bandwidth and result in interfere with each other. Design of UWB antenna with band-notched function has become a hot spot. This thesis mainly focuses on the design of UWB antenna with notched bands and small size for the UWB system.To avoid the interferences of WiMAX(3.3-3.7GHz) and WLAN(5.15-5.825GHz)systems to UWB systems, a compact coplanar-waveguide-fed monopole UWB antenna with dual band-notched function is firstly presented. The antenna only occupies a volume of25mm×20mm×1mm. Two types of simple slots, L-shaped and semicircular, are cut in the radiating patch to create dual band-notched function in3.2-3.8GHz for WiMAX and5.1-5.8GHz for WLAN. Experimental results show that the VSWR in the work band of3-14GHz less than2. It is shown that the proposed antenna has almost omnidirectional radiation pattern in H plane and a good stable gain except two band-stops over the whole band. Effects of several critical parameters of the antenna on its performance are analyzed by using the CST software. The antenna prototype is manufactured. Simulated and measured results indicate that the antenna meets the UWB system requirements.UWB antennas with triple band-notched based on the coplanar waveguide fed and tunable band-notched characteristics based on the microstrip fed are proposed. By adding two L-shapped and C-shapped on the radiating patch and adding a U-shapped in the feed line, Triple band-notched are achieved. Effects of several critical parameters of the antenna on the frequency ranges of the notched bands are also analyzed. UWB antenna with having tunable band-notched function use edge feed microstrip line. By adding slot and clipped corner on the ground. The characters of Ultra bandwidth and band notched are achieved. Adding two RF switches on the slot. Achieving UWB antenna when closed the switch. Then opening the switch, UWB antenna with band-notched is got. Tunable band-notched is achieved by adding different capacitors. Two antenna prototypes are implemented, the measured results are in good agreement with the simulated results. Finally, some drawbacks of these antennas are pointed out, and the lots of problems remain to be studied further are given. |
