Research And Design Of Base Station Antenna For MIMO Applications

The rapid development of such mobile devices as laptop、smartphone、handheld game players and increasing numbers of customers for wireless access bring in great challenge for quality and speed of wireless communications. As an important part of wireless communication systems, properties of base station antenna greatly affect how well communications could be. The adoption of MIMO(multiple input multiple output) scheme can raise communication speed and add to signal capacity with the usage of same frequency sources. The combination of MIMO technology and base station antennas provides feasibility for current need of high speed communications. Thus, it is in great need to design high-performance antenna elements and arrays for base station communications.In the beginning, this thesis introduces concept and practical applications of base station antenna and presents different combinations of MIMO systems and base station antennas.A MIMO antenna array that has high gain、wide impedance bandwidth on the basis of magneto-electric antenna is also introduced. The proposed design is fabricated and tested, in line with which the results satisfy the requirement for bandwidth、gain、antenna elements、maximum power capacity.To lucubrate the magneto-electric antenna, working principle and currency distributions are analyzed with the help of HFSS(High Frequency Structure Simulator). On account of above achievement, a MIMO antenna array with band notch property is designed. It is stressed that this antenna arrays has wide range of frequency adjustment while changing the size of window shaped structure. The measured results agree well with the simulated ones, both of which exhibit excellent operating characteristics.U-shaped slots are adopted to project a dual band base station antenna for WLAN and WIMAX applications. Except for the directional and high gain property for desired frequencies, requirements for various communications bands could be accomplished with the aid of changing U-shaped slots dimensions. The flexible adjustment of operating frequency together with high gain and directional radiation make it a candidate for changeable circumstances of base station communications. It should be mentioned that there exists beam instability for high working band which perhaps restrict its applications for some high demandingness regions. And it may due to the shielding effect of small U-shaped slots that result in the appearance of beam unsteadiness.Sierpinski fractal structure is finally used for avoiding beam instability while maintaining dual-band characteristics. Because of self-symmetrical and multiple bands properties, a base station antenna element that simultaneously works at 2.4GHz and 5.2GHz is designed. And to realize plans for large-capacity communications, dual band and dual linear polarized antenna element and array are made and measured. The measured results greatly satisfy high capacity need for MIMO antenna systems with finite space, which coincides with our original intention of high performance design.