Ku频段卫星通信链路计算

卫星通信具有容量大、成本低、抗干扰性能强、覆盖面积广和通信距离远等优势,已成为舰船通信的重要手段。针对Ku频段卫星通信的特点,提出了一种链路计算方法,并给出了岸基发送站、卫星转发器和接收系统的参数,通过实例分析,计算上行发送站的EIRP、接收站天线的方位、链路降雨衰减、链路载噪比及链路余量等,从而设计出合理的链路预算。     

Ka频段卫星通信地空链路的大气衰减

在卫星通信系统的设计中,设计人员往往更关心降雨对电波传播造成的降雨衰减,而易忽略在一般情况下晴空大气对卫星通信地空链路微波传播的影响。但是当系统的链路余度较小、天线仰角较低的情况下,应考虑晴空大气造成的衰减。论述了 Ka 频段卫星通信链路大气衰减的计算方法,给出了计算结果,可供从事类似工作的相关人员参考。     

降雨对卫星链路的影响分析

Ku 频段的卫星通信系统在我国已经普遍使用，目前正朝着更高的 Ka 频段发展。随着 频率的提高，降雨对卫星通信链路的影响会更加严重，是系统设计必须考虑的重要因素之一。针对降雨 带来的信号衰减、地球站天线 G/T 值的变化以及对卫星通信上/下行链路载噪比的影响进行了分析，并 利用 ITU-R 最新给出的雨衰减预报模式，给出了定量计算方法。     

三亚Ka波段卫星遥感信号降雨衰减的研究

Ka波段卫星下行遥感信号受降雨衰减影响严重,在设计信道链路和执行遥感数据接收任务时,需要考虑Ka波段雨衰问题。基于国际电信联盟无线电通信部门(ITU-R)提供的雨衰模型,结合三亚某地面站Ka波段卫星遥感数据接收设备,利用Matlab处理时间概率0.01%的降雨量数据,模拟三亚Ka波段卫星下行信号的降雨衰减率,分析降雨衰减值随天线接收仰角的变化,为设计三亚Ka波段下行信道抗雨衰余量提供了参考。同时结合自动气象站降雨观测数据,研究不同等级降雨量时的雨衰情况,为制定三亚Ka波段卫星遥感信号应对雨衰的措施提供了依据。     

移动通信平台Ku/C双波段自动切换卫星通信系统设计

本文对双波段车载卫星通信系统的研究背景及气象系统现有的车载卫星通信系统的现状进行了介绍．并对车载Ku／C双波段卫星通信系统的可行性进行了深入的分析,然后对车载卫星通信天线的选型．Ku／C双波段车载卫星通信系统中天线部分、馈源部分和射频部分的设计行了分析和测试．提出卫星链路上几种影响数据传输效率的因素及解决办法．实现了车载卫星通信系统的Ku／C双波段切换．并对卫星通信系统各项性能指标测试的方法进行了介绍。实际测试各项性能指标达到了卫星公司的入网测试要求．验证7Ku／C双波段车载卫星通信系统的设计是可行的。     

一种LEO-S频段星地链路传输体制研究

由于低轨卫星系统(LEO)具有传输时延短、传输损耗低等优点，对于实现宽带业务、终端的小型化非常有利；另外，S 频段抗雨衰能力强，天线尺寸小造价低，使其很适合卫星移动电话、区域内多用户间数据等业务通信场合。本文针对目前低轨卫星通信需求提出了一种 LEO_S 频段星地链路传输体制，结合用户数量及传输速率要求，对上下行链路的传输体制进行了研究，计算了上下行链路的余量，并有针对性地提出了星地链路抗干扰措施。     

下行链路雨衰对卫星地面接收系统噪声温度和噪声功率的影响

卫星下行链路降雨除了导致信号受到衰减外,还会升高卫星地面接收机的噪声温度,从而进一步恶化卫星信道的通信质量、本文就下行链路雨衰对卫星地面接收系统噪声的影响进行了研究,并基于ITU—R推荐的降雨衰减预测模型,对一个实例进行了仿真、分析,得到了雨中噪声温度、噪声功率与极化方式、工作频率、接收天线仰角、降雨强度之间的变化关系．     

卫星转发器增益衰减对转发式卫星导航通信系统入站链路性能影响分析

在卫星通信系统中,卫星是一个很重要的环节,卫星转发器的参数在一定程度上决定着整个系统的性能.转发式卫星导航系统是一个导航通信一体化的系统,通信系统中的微小卫星终端由于其发射天线波束宽,从邻星干扰方面考虑,远区卫星还处在微小卫星终端的主瓣内,因此发射功率受到了限制,是一个很明显的上行功率受限的系统.为了缓解对发射终端的压力,文中对卫星转发器的增益表减档对整个通信系统的性能影响进行了分析,得到的结果显示,在转发器增益衰减档减小时,整个系统的性能可以得到提高,试验结果也表明,对于微小卫星终端系统,卫星转发器的增益档设置在2dB左右比较适宜.     

Ka频段卫星通信系统降雨衰减分析

Ka频段卫星通信因其具有可提供的带宽大(3.5GHz)、通信容量大、波束窄、终端尺寸小,轨道平面内可容纳的卫星多和抗干扰能力强等优势成为未来卫星通信的必然趋势。Ka频段卫星通信面临的一个巨大挑战在于它受气象因素的影响大,这一度使研究人员认为Ka频段卫星通信是不可能实现的。降雨、闪烁、大气吸收等因素都会导致Ka频段地空链路信道质量的恶化。根据Ka频段卫星通信的特点,分析了降雨衰减的特性,提出了几种抗雨衰的办法。     

CAPS地面站天线跟踪卫星

地面站是卫星导航通信系统中必不可少的重要组成部分,具备接收、发射信号,监控卫星以及与地面通信网络通信交换等功能,地面站的大天线对星跟踪是卫星通信开展的基础。针对卫星地面站的重要性,介绍了CAPS(中国区域定位系统)位于北京的卫星通信地面站天线对星跟踪系统,利用该天线对准亚太I号卫星时的方位角、俯仰角以及系统AGC电平值分析了亚太I号卫星的运动轨迹,亚太I号卫星的漂移幅度在不断的增大。     

海上云层和降水对船载高频段卫星通信的影响

介绍了海洋云层和降水的特点以及云层和降水对电波吸收的影响;描述了海洋层状雨和对流雨的降雨空间结构状态以及对高频段卫星通信雨衰的影响;分析了高频段卫星通信雨衰原因,指出了电磁波吸收、热噪声和去极化是影响高频段雨衰的重要方面,并针对海上工作环境特点提出了上行功率控制、频率分集、速率分集、自适应调制等抗雨衰方法.     

30/20 GHz Band SCPC Satellite Communication Using Small Earth Stations

This paper presents a domestic satellite communication system accommodating numerous 30/20 GHz band small earth stations emphasizing the system outline, the use of multiple-access (MA) techniques. It also describes associated earth station configurations, equipment performance, and experimental results using the Japanese CS (medium capacity communications satellite for experimental purposes). Two kinds of earth stations are employed in this system, a small earth terminal (SET) and a master earth station (MES). The SET, which has an antenna about 2 m in diameter, is placed near a subscriber. The MES, which has an 11.5 m diameter antenna, is connected to the terrestrial telephone network through a satellite telephone switching center (STC). There are about 50 two-way channels with bit rates of 32 kbits/s which are achieved through the use of a 30/20 GHz band transponder whose EIRP is about 71.5 dBm, aG/Tof about 2.7 dB/K and an SET's antenna diameter of 1.8 m. This results in a system availability of 99.5 percent under typical Japanese statistical rain attenuation data. To enable a demand-assigned MA technique to be employed in this system, a single channel per carrier (SCPC) is selected, taking into consideration power efficiency of the SET, flexibility of system configurations, and the adaptability of the adaptive power control during rainy periods.     

星地激光通信中多光束发射的最优发送

在多光束发射系统中,发送天线获得信道状态信息能够提高信道增益,有效克服大气湍流对星地激光通信的影响,提高系统的误码率性能。文章提出一种基于信道互易理论让发送天线获得信道状态信息的方法,然后根据信道状态信息,对发送光束进行最优选择,提高发射功率的利用率,改善信噪比,降低误码率。仿真结果表明,在发送端对发送天线进行最优选择,能够降低星地激光通信的误码率,提高通信系统的性能。     

Rain compensation algorithm for ACTS mobile terminal

The initial advanced communication technology satellite (ACTS) mobile terminal (AMT) demonstrations will involve two-way communications between the high-bit-rate link evaluation terminal (HBR-LET), which is a fixed terminal (FT), and a van-housed mobile terminal (MT). The HBR-LET has the capability of adjusting its transmitted uplink power over an approximately 10 dB range to compensate for forward uplink rain attenuation. However, because of size and weight limitations, the MET cannot use power control as a rain compensation technique. Consequently, the AMT rain compensation algorithm (RCA) is based on a formula for varying the transmitted data rate in either direction to maintain link performance within acceptable limits. The objective of the AMT RCA is to ensure reliable operation in both the forward and return directions despite the possibility of uplink or downlink fading due to rain events in the vicinity of the FT or MT. In particular, the RCA must maintain at least a 3 dB link margin at the highest possible transmission rate (AMT can operate at 9.6, 4.8, or 2.4 kb/s) permitted by the prevailing channel conditions. The 3 dB minimum link margin is a system design safety factor to accommodate conceivable implementation losses     

Uplink power control based on receiver noise measurements insatellite communication systems

The authors describe a novel procedure for uplink power control in a multicarrier satellite communication system. The purpose of uplink power control is to compensate for rain attenuation so that all carriers are at the same power level at the input of the satellite nonlinear amplifier. The presence and amount of rain attenuation is predicted by continuous monitoring of the receiver noise power. Attractive features of the proposed scheme include its conceptual simplicity, ease of implementation, applicability to a wide variety of scenarios and avoidance of the undesirable overhead coordination, and delay requirements associated with previously used methods     

The role of rain in satellite communications

The most fundamental obstacle encountered in design of satellite communication systems at frequencies above 10 GHz is attenuation by rain. The microwave power radiated toward an earth station, being limited by factors such as available primary power and size of antenna on the satellite, is insufficient, with present technology, to overcome the large attenuation produced by intense rain cells on the earth-space path. The resultant loss of signal makes for unreliable transmission. In what follows, methods of measurement of this attenuation at various frequencies and a technique called path diversity that substantially improves the reliability are presented. Other degradations produced by rain, such as depolarization, interference, increase in earth-station noise, and deterioration of earth-station antenna performance, are also discussed.     

30/20-GHz domestic satellite communication system in the public communication network of Japan: Design and operation

Nippon Telegraph and Telephone Public Corporation (NTT) initiated the world's first 30/20-GHz domestic satellite communication system for commercial use, using CS-2s launched from Japan in 1983. This system utilizes TDMA digital communication in the trunk transmission route of the public communication network, which includes interregional-center routes and main-island-to-remoteisland routes. Small transportable earth stations enable easy access to the public communication network from any place in Japan. The adoption of the 30/20-GHz band enables use of a compact on-board antenna that has a shaped beam that effectively covers the main islands of Japan. It also enables the use of high-performance, compact antennas at the earth stations. These antennas can easily be installed on the roof of telephone offices or set on motor vehicles. One apparent disadvantage of using the 30/20-GHz band is rain attenuation. However, NTT has realized a commercial system that is affected very little by rain attenuation. This was accomplished by utilizing high-performance radio equipment and by concentrating on appropriate system design. Adoption of the 30/20-GHz band is quite significant because the wide bandwidth available enables construction of high-capacity economical transmission systems. It also enables use of small antennas, which allow construction of high-speed digital direct-to-user transmission systems using small earth stations. These expand the application of the domestic satellite communication system to even small service areas. Therefore, NTT considers satellite communication to be of primary importance for its proposed digital communication network, and has begun research on a high-capacity, economical, multibeam communication satellite system using the 30/20-GHz band. This paper describes the 30/20-GHz band radio technology, digital communication technology utilizing high-speed TDMA, and operational technology in the public communication network.     

Ku频段卫星雨衰计算及自动观测系统设计

随着Ku频段卫星通信系统的使用,雨衰对卫星传输链路的影响已经成为卫星通信系统设计与使用过程中的重要影响因素。针对雨衰对Ku频段卫星通信系统可用性的影响,首先对雨衰的产生原因及其对卫星传输链路的影响进行了简要介绍,其次对国际电信联盟推荐的雨衰估算方法进行了分析,最后提出了Ku频段卫星链路传输特性自动观测系统的设计方案。