Study Of Narrow Beam Base Station Antenna Based On Imt-Advanced Systems For High Speed Railway Communication

IMT-Advanced systems, also called4G, are the fourth generation mobile communication systems, which possess bigger system capacity and higher data rate. The peak rate of1Gbps is achieved in low speed condition or the hotspot coverage place.100Mbps is realized in high speed condition or the wide area coverage scene. At that time, IMT-Advanced systems can support a wider range of business applications, and provide higher quality communications service.The environment high speed train running in is a special communication field. Higher requirements for communication system are put forward because of the high-speed movement of the train. In order to solve the problems of dropping calls and failed calls in the communication system, the narrow beam antenna was usually installed along the railway. This can improve the quality of communication with covering in chain along the railway. Thus, the narrow beam base station antenna is an integral part of high-speed rail communication.So the study of the narrow beam base station antenna based on IMT-Advanced system is very important.This paper summarizes the common unit forms used in the base station antenna.Then the printed dipole antenna is used as a high-speed rail antenna unit. The antenna is simulated and analyzed with the electromagnetic simulation software, which is based on FEM. Following that, the project of entire base station antenna design is determined. The antenna’s bandwidth is expanded by cutting corner, bending and changing the balun’s width. The simulation results show that the dual-polarized antenna element owns the performance:in the1.71-2.69GHz frequency ranges VSWR less than1.5, isolation level more than28dB.The performance meets the communication industry standard. Then the antenna radiation pattern is analyzed. The results show that the antenna has a good horizontal plane radiation characteristic.Two methods realized narrow beam width are analyzed:using reflector with parabolic cylinder and arraying in the horizontal plane. The way arraying in horizontal plane is used to achieve the desired pattern at last. According to the desired gain and vertical beam width, six units are used to meet the vertical plane radiation. The simulation results show that the array owns good radiation performance in the vertical and horizontal plane.The array meets the design requirements.Finally, taking into the VSWR, port isolation, beam width, antenna gain, cross-polarization ratio, front to back ratio of the base antenna, the optimal parameters of the array is determined with simulating, the design and research of the entire dual polarized base station antenna is completed.