Ka频段点波束天线指向精度对星地数传链路的影响分析

Analysis of Influence on Satellite-to-earth Date Transmission Link by Directing Precision of Ka-band Spot Beam Antenna

为满足低轨遥感卫星海量数据的高速下传需求,Ka频段双圆极化频率复用数传技术已被逐步应用,而其使用的机械式点波束数传天线对指向精度和极化隔离度有很高的指标要求。文章对Ka频段点波束天线的辐射增益和交叉极化隔离等特性进行了讨论,从工程应用的角度定量研究了交叉极化的产生及其对链路极化损耗、链路余量和链路可用率的影响,重点分析了Ka频段点波束天线在不同指向精度时对不同地面站极化复用数传链路的影响。Ka频段点波束天线指向精度优于1°时,只能满足北京地面站99.0%链路可用率的可靠数据传输,可以满足喀什地面站99.9%链路可用率的可靠数据传输。文章的分析结果可为低轨遥感卫星Ka频段点波束天线的设计与研制提供参考,尤其是可为Ka频段双极化复用数传链路的总体设计和卫星任务规划提供分析依据。

To meet the LEO remote sensing satellites’ demand for mass and high-rate data transmission to ground,the technology of Ka-band dual circular polarization frequency multiplexing has been gradually developed and utilized in engineering design.As an important part,the mechanical spot beam data transmission antenna of satellite should possess good performance in the directing precision and cross polarization discrimination（XPD）.This paper discusses the performance of radiation gain and XPD of the antenna.According to the remote sensing satellite’s engineering applications,the influences on the data transmission link caused by the polarization loss and the different directing errors of antenna are investigated.For the directing precision of antenna better than 1°,the link availability can reach 99.9% when the ground station is locates in droughty area such as Kashi,but less than 99.0%in pluvious area such as Beijing.These results can be utilized in the development of Ka-band spot beam antenna of LEO remote sensing satellites,and especially can provide the scientific references for the system design of the satellite-to-earth data transmission link and the mission planning.