共享铁塔基站天线对在线监测设备的电磁干扰及防护

Electromagnetic Interference of Base Station Antenna to On-line Monitoring Equipment on Shared Tower and Protection

共享铁塔将电力和通信设备集成一体,其新增的基站天线与铁塔上原有的输电线路在线监测设备近距离架设,不可避免地会对在线监测设备产生电磁干扰。根据现有在线监测设备的电磁兼容标准,分析了基站天线对在线监测设备的干扰机理,建议以射频辐射抗扰度10V/m为抗干扰设计限值。结合天线原理,推导了基站天线场源的数学表征式,进而提出了多基站天线辐射下,电大尺寸金属散射体在空间任一点处散射场求解的数学模型。采用PO-MoM混合算法对提出的数学模型进行求解,并通过电波暗室实验对其进行验证,结果表明,数学模型的全局最大相对偏差值随频率的增加而增大,在2 600 MHz时为8.33%。以山东共享铁塔为算例,分析了铁塔塔头型式、天线功率、天线倾角3种工况下在线监测设备处电场强度变化规律,并以此为依据,建议将天线与在线监测设备之间的防护间距定为4 m。

A shared tower integrates power and communication equipment, and its new base station antenna is erected close to the online monitoring equipment for original transmission lines on the tower, which will inevitably produce electromagnetic interference to the online monitoring equipment. According to the EMC standard of existing on-line monitoring equipment, the interference mechanism of base station antenna to on-line monitoring equipment is analyzed, and it is suggested to take the immunity of RF radiation 10 V/m as the design limit of anti-interference. Based on the principle of antenna, a mathematical expression of the field source of base station antenna is derived, and a mathematical model for solving the scattering field of electrically large metal scatterer at any point in space under the radiation of multi-base-station antenna is proposed. The PO-Mo M hybrid algorithm is used to solve the mathematical model, which is verified by anechoic chamber experiments. The results show that the global maximum relative deviation of the mathematical model increases with the increase of frequency, which is 8.33% at 2 600 MHz. Moreover, a Shandong shared tower is taken as an example to analyze the variation rule of electric field intensity at the on-line monitoring equipment under three working conditions of tower head type, antenna power, and antenna inclination. Based on this, it is suggested that the protection distance between the antenna and on-line monitoring equipment be set as 4 m.