Design And Research Of Novel Multi-Band Antenna For Mobile Communications

With the rapid development of the mobile communications system,it is foreseeable that the second-generation mobile telecommunication system(2G),3G and wireless LAN systems(WLAN) will coexist for a long period in China's mobile communication market in the future.Therefore,the multi-frequency band repeater antennas or broadband base station antennas are needed to be able to cover 2G/3G/WLAN,in order to meet the needs of compatibility of different mobile communications wireless networks.In this dissertation,a bow-tie antenna working in the 2G/3G/WLAN bands synchronously is presented and designed,the antenna also covers WIMAX band(2.5GHz-2.69GHz) which is a new standard for 3G..The power divider and the phase shifter of the base station feeding network and the electrical downtilt of the base station array antenna are also analyzed and researched. Firstly,a double-sided printing new bow-tie antenna with asymmetric overlapped double arms is presented and designed,on the bases of analysis of known broadband bow-tie antennas.Two different feed modes,microstrip feed and coaxial feed are considered for the design,and the corresponding feed matching network is designed. Simulations show that the antenna exhibits good performances on impedance characteristics and radiation patterns at the 2G band(824～960MHz),3G band (1.7GHz～2.2GHz),WLAN band(2.4～2.5GHz)and WIMAX band(2.5GHz-2.69GHz).Secondly,a new bow-tie antenna which covers both the high band and the low band of WLAN are analyzed and designed by changing the configuration and dimension of the bow-tie antenna.We also design a bow-tie antenna for GPS,3G and WLAN.A cylindrical bow-tie antenna which covers 2G,3G,WLAN and WIMAX is analyzed and designed based on the printed plane antenna,the impedance characteristics and the radiation patterns of the cylindrical antenna meets the needs of mobile communications.The impact of arms overlapping on the work-band,the impedance conversion and arms asymmetric on the beam tilt are studied detailed,and such antenna design methodology is also given.Finally,the 3G base station feeding network is researched in this paper,and power divider and phase shifter are designed and simulated.A one-six T-power divider is designed firstly,and then analyze a six elements repeater antenna arrays with fastness downtilt combining the T-power divider.We analyze the speculative knowledge of phase shifter and design a stripline dielectric phase shifter,then we study beam electrical downtilt by combining the simulated results of phase shifter with the base station antenna arrays.