The Application Of The EBG Structure In Reducing The Profile Height Of The Base Station Antenna Element

The base station antennas are the important part in the mobile communication system,and their performance directly influences the quality of the mobile communication network.With the deepening of the base station antenna applications, the wide band, the electronictilting and the community of different systems trend of the base station antennas bringforward strict demand to the miniaturization of the antennas. The emphasis and difficulty ofthe miniaturization are the reduction of the antenna element height. The electromagneticbandgap (EBG) structure has the in-phase reflection phase characteristic in some frequency,so if it is used as the ground plane, the dipole height can be reduced radically.This paper focuses on the design of the dipole height reduction technique. Firstly, thispaper introduces the history of the EBG structure, the in-phase reflection phase and thesurface wave band gap characteristics and their measured method. Then basing on the classicmushroom type EBG structure, this paper designs a novel EBG structure (DD-EBG) withlarge in-phase reflection phase and designs a method to determine the EBG structure size incase of the best performance of the dipole. Then we reduces the size of the EBG ground plane,redesigns the baluns for the dipole, and optimizes the vias of the EBG structure to improvethe performance of the dipole further. Finally, an EBG structure backed dipole model isdesigned with half height of the original dipole.This paper manufactures the prototype of the EBG structure and the dipole and thenmeasures them. The measured results show: within the1.85-2.5GHz, the VSWR is less than1.6, the isolation is higher than25dB, the gain is higher than7.5dBi, the beam width of thehorizontal and vertical plane is between66.5-76.5degrees, the F/B ratio is between20-27dB,the cross-polarization ratio is higher than13dB.The results can satisfy the demand of the basestation antennas basically. Finally, this paper spreads the technique to other two dipoleelements to reduce the height of the both while keep their performance not worse than theoriginal dipoles. The technique we design can be widely used in the dipole elements in thebase station antennas, and it can instruct the designers in engineering practice.