Research On Ultra-Wide Band Antenna And Dual-band Shared-Aperture Antenna

Nowadays,the wireless system terminals have been developed to the compact,multi-functional and smart trend.Antenna plays an essential role in the terminals,and it usually occupies a large space,particularly in the HF/VHF and multiband radio systems.Because of all these,this thesis concentrates on the applications of ultra-wide band(UWB)antenna and dual-band antenna.We have researched the compact reconfigurable UWB VHF/UHF antenna,the UWB dual-polarized wide beam antenna and the shared-aperture dual-band antenna for terrestrial trunked radio(TETRA)and wireless local area network(WLAN)communication.The details involve three aspects,listed as follows:Firstly,for the UWB(30 MHz?3 GHz)VHF/UHF antenna,this thesis explained the detailed design processings of the antenna from principles and simulations.We proposed the mechanical folding structure with the passive matching networks to design the UWB antenna,to make it work in separate frequency band.This is to say,the antenna can cover 100:1 impedance bandwidth by using the different structure mode with the different matching networks.In addition,the antenna can be used in mobile travel.Because of the folding structure,it is compact and easy to carry.Secondly,for the broadband dual-polarized antenna used in communication,we have designed an improved dual-polarized dipole antenna to broaden the bandwidth and beam width of antenna by using a trapezoidal ground.The simulation results indicate that the-10 dB bandwidth covers from 1.405 GHz to 4.05 GHz,and it also has a wide beam,good isolation and low cross polarization performance.Thirdly,for the TETRA/WLAN communication,we have researched a TETRA/WLAN multi-antenna terminal used shared-aperture technology.The TETRA antenna worked on 806?866 MHz,while the three WLAN antennas which used multiple-input multiple-output(MIMO)technology worked on 5.15?5.825 GHz.The measured and simulated results indicate that the antenna can cover TETRA 800 MHz and WLAN 5 GHz perfectly.Moreover,the antenna terminal has good isolations,envelope correlation coefficient(ECCs)and radiation performance.