Design Of Narrow Beam High Gain Dual-frequency Antenna For High-speed Railway

The rapid development of high-speed railway has brought new opportunities for mobile communications and also imposed serve challenges on the communication systems. Due to the high-speed and complex geographic conditions, and the influences of multipath effect and Doppler shift, the signals of the wireless channels are greatly influenced and declined sharply. Thus, the area coverage along the high-speed train should be reasonably planned to ensure the reliability of communication. Base station antennas are the key component of mobile communication system, and with the continuous improvements in network capacity and quality of the high-speed railway network, more requirements are put forward for the base station antenna.In this paper the microwave propagation characteristics under high-speed environment are analyzed and the common ways of high-speed network coverage are also researched. In order to reduce the switching frequencies, the use of remote fiber-optic technique is introduced and the coverage can be enhanced.This paper mainly focuses on the realize of the narrow-beam, high-gain and dual-band antenna. Firstly, the solution feasibilities are discussed from the point of array arrangement and several array forms are proposed including diamond from, dual-listed form, nested form and other forms. Then the above forms are modeled, simulated and analyzed by EM simulation software CST. After many simulation comparisons and comprehensive analysis, it is found that dual-row nested form has the most satisfactory features. And an antenna prototype is fabricated based on the optimization results. During the fabrication, the beam-forming operation is realized by adjusting the phase of the antenna element and the antenna down tilt is adjusted by the phase shifters. In the end, details of measured results are given and analyzed, the differences between measured and simulated results are also discussed through theoretical analysis.