Closed-Loop Transmitting Power Control System for K-band Satellite Communications

In order to cope with K-band link loss variations and also to improve link reliability, a new closed-loop satellite access power control system is proposed. This system controls Earth station transmitting power so that the overall satellite link quality, such as S/N or error rate, converges to the stipulated value. Satellite transmitting power is also optimized by this control, enabling a considerable increase in transmission capacity and improvement in link reliability.     

The Tactical Communications Satellite

Early in 1969 the U. S. Air Force placed into synchronous orbit the largest communications satellite built to date. This vehicle, the tactical communications satellite (TACSAT), together with a variety of ground terminals, is designed to test experimentally and develop tactical communications concepts for all military services. This paper describes the spacecraft design focusing on the communications repeater. Measured performance characteristics affecting communications utilization of the spacecraft are presented.     

Communication Subsystem Design Trends for the Defense Satellite Communications Program

The Initial Defense Communication Satellite Program (IDCSP) hasbeen implemented successfully and is handling unique and vital militaryary communications. Tradeoff studies now being made are intended todefine the characteristics of the next phases of the Defense Satellite Communications Program (DSCP). This paper discusses briefly thecommunication subsystem design of the IDCSP for backgroundfor-information, and then discusses the design trends for future phases of the DSCP.The communication subsystem for the IDCSP is characterized bya single hard-limiting, low-power repeater with a toroidal patternantenna. Future trends in design will be toward multiple beams andmultiple repeaters with very wide bandwidths, high-powerquasilinear operation, and highly directive antennas. Several alternatetransponder configurations are evaluated in this paper, and an illustrativeive example is shown. Although long life is essential to future systems,as it was to the IDCSP, the trend will be to adding more complexity inthe satellite to increase the system capacity, while at the same timerequiring less complexity in earth terminals.     

A Note on the Effects of the Ionosphere on Satellite Orbital Corrections in Near-Real Time

The influence of ionospheric irregularities,e.g., sudden increase of electron content, onthe accurate determination of the position ofa satellite is being investigated. In this note amethod is presented whereby these effects areeasily accounted for in near-real time withoutthe need to know their detail structure.     

Overview of Commercial Satellite Communications

The period from Arthur Clarke's 1945 prediction of geosynchronous satellite communications covering the entire planet until satellites were stationed over the Atlantic, Pacific, and Indian Oceans was less than 25 years. In the following 15 year period, satellite communications has affected all of us. Most international calls are carried by satellite. Much of the television that we watch has been relayed, processed, or distributed by satellite. In fact, many of us who live in cabled cities can choose among 50 channels or more for viewing on a particular night, largely brought to us by satellite. Some morning papers, radio programs, and basic weather data appear coast to coast rapidly because of the satellite. Even while we sleep, computers in an increasing number of business offices are talking to each other by satellite. Virtually the whole world, from the busiest urban center to the most remote island, can be interconnected by satellite communications networks capable of providing economical and reliable transmission of communications signals, including voice, data, electronic mail, and video. The satellite's advantages of distance insensitivity, point-to-multipoint capability, and improved quality over long distances are unique. These facts have led Clarke to speculate on the future impact of satellite communications in The View from Serendip (1977): I submit . . . that the eventual impact of the communications satellite upon the whole human race will be at least as great as that of the telephone upon the so-called developed societies.     

System Design for Improved Extra-Terrestrial Communications

This paper describes a proposed system for improved exo-ionospheric communications. The dynamic magneto-ionic character of the channel is considered, in particular, the multipath situation arising therefrom. An ideal matched filter is found, matched to the multipath structure and the dynamics of the exo-ionospheric channel. The improvement in the signal-to-noise ratio through the matched filter is calculated. It is seen to depend on the quotient of the input signal to the bandwidths of the ``measuring' filter and the ``integrating' filter. Further advantages are shown to accrue from signal processing at the transmitter involving both increases in range, and, in particular, secure coding possibilities.     

Military Satellite Communications Using Small Earth Terminals

Satellite communications technology has reached the stage at which it is feasible to develop a reliable military tactical communications system using small transportable Earth terminals. This paper discusses the design considerations involved for a multiple-access system, with particular reference to the Earth terminals.     

Compensators for Bandpass Nonlinearities in Satellite Communications

The characteristics of optimum compensators for bandpass non-linearities are described. A predistortion compensator to reduce the nonlinear phase and envelope distortion at the output of a traveling-wave tube (TWT) is developed, and a possible implementation as a simple network of power law devices in cascade with the input to the TWT is given. The overall compensated characteristic of the TWT approximates that of a piecewise linear limiter with a small phase shift. A computer simulation shows that the compensated system yields 0.3 to 0.5-dB improvement in performance of a 2-phase coherent phase shift keying (CPSK) system over the uncompensated system.     

Artificial Site Shielding for Communications Satellite Earth Stations

A method of reducing the possibilities of interference between earth stations and microwave radio-relay stations by the use of pit shielding has been investigated. A pit was constructed containing a 32-foot diameter antenna. Measurements are reported which indicate a shielding advantage of at least 25 dB. A siting example under actual conditions is given.     

Japan's CS (Sakura) Communications Satellite Experiments

The Japanese Communications Satellite (CS), called Sakura, is a "Medium Capacity Communications Satellite for Experimental Purposes" and is the first experimental communications satellite in which 30/20 GHz bands were adopted and were developed for practical domestic use. Large scale field trials have been carried out for more than three years in order to evaluate 30/20 GHz (Ka-band) and 6/4 GHz (C-band) domestic satellite communications system technologies under actual operational conditions by using the CS Sakura launched in December 1977. Through the various experiments on Kand C-band large fixed and small transportable Earth station systems, satellite control experiments, and Ka-band propagation measurements, it has been verified that the medium capacity satellite communications system meets the design objectives.     

绕飞监测小卫星姿轨联合自适应控制研究

针对小卫星近距操作过程中轨道和姿态控制问题,建立了小卫星相对轨道和姿态的误差动力学模型。采用相对轨道和姿态联合控制策略,并考虑小卫星作业过程中质量和转动惯量的不确定性,设计了自适应输出反馈控制律,并证明了其稳定性。最后以对圆轨道目标星近距离环航为例,根据作业任务和姿态指向要求,设计了小卫星相对轨道和姿态的期望运动,应用所提出的控制策略及相应的控制律进行了数值仿真。结果表明,系统跟踪误差能够较快收敛,说明了控制策略的有效性。     

Optimization of Coverage Pattern for Regional Communications Satellite

An optimization problem of an antenna coverage pattern for a regional communications satellite when an antenna-pointing error exists is discussed. A new performance measure is introduced to evaluate the coverage pattern. This measure is defined as the statistical mean of the ratio between two areas, the full service area and the part of it covered by the antenna. The optimum coverage pattern which maximizes this measure under certain constraint is obtained. The results of numerical calculations are included to demonstrate the technique.     

构建卫星状态诊断系统的一种实现方法

简要分析了卫星状态诊断专家系统在卫星管理工作中的必要性,说明了其应用范围和基本功能,着重介绍了该系统的设计与实现方法,说明了该系统在卫星管理过程中的应用情况。     

Air-Ground, Ground-Air Communications Using Pseudo-Noise Through a Satellite

An air-ground, ground-air communications system that utilizes a satellite and a central control facility is described. The double-hop pseudo-noise system advantages, including equal sharing of power, use of frequency translating repeaters, optimum multipath rejection, and acceptable power densities on the ground are discussed. The selection of code division is presented together with an analysis of signal-to-noise ratios with a varied input. Modulation schemes are discussed, pro and con, and the effective radiated power versus antenna sizes for several combinations are analyzed.     

Satellite Constellation Design with Adaptively Continuous Ant System Algorithm

The ant system algorithm （ASA） has proved to be a novel meta-heuristic algorithm to solve many multivariable problems. In this paper, the earth coverage of satellite constellation is analyzed and a n ＋ 1^ -fold coverage rate is put forward to evaluate the coverage performance of a satellite constellation. An optimization model of constellation parameters is established on the basis of the coverage performance. As a newly developed method, ASA can be applied to optimize the constellation parameters. In order to improve the ASA, a rule for adaptive number of ants is proposed, by which the search range is obviously enlarged and the convergence speed increased. Simulation results have shown that the ASA is more quick and efficient than other methodV211.71s.     

小卫星“微型核”CMOS功率放大器设计

在以往的小卫星设计中,构成卫星的最基本单元大都是由分立的元器件组成。本文采用SMIC 0．18μm Si CMOS工艺,设计了一种用于星载信息电子系统的高效率功率放大器,在3．3V电源电压下,输入功率为0dBm时,输出功率为21．4dBm,附加功率效率为60％,输入端反射系数S11=-35dB,可满足星载信息电子系统要求。     

基于自适应连续蚁群算法的卫星星座设计(英文)

蚁群算法是一种解决多变量问题的新型启发式仿生算法。本文分析了卫星对地面的覆盖条件,提出用——/(n 1)重覆盖率来评价星座的覆盖性能,建立了以覆盖性能为目标函数的卫星星座参数优化模型。采用蚁群算法对卫星星座参数进行优化,为星座优化问题提供了一种新方法。在连续蚁群算法的基础上对算法进行改进,提出蚂蚁种群数量的自适应准则,有效的提高了搜索范围与收敛速度。通过仿真表明,与其他方法相比,蚁群算法在星座参数优化有着明显的效率。     

基于Modbus协议的通信软件设计

分析Modbus协议的ASCII模式通信,设计ASCII信息帧的结构,采用C#语言中的SerialPort控件实现Modbus协议的串口通信软件,经过和C805lF330单片机开发板的多次运行测试,结果表明主-从机通信过程稳定性好,ASCII信息数据传输安全可靠,实现了Modbus协议的主从式通信。     

基于卫星授时控制器的设计与实现

针对一些小型试验场或舰船上的条件局限性,对授时、控制等参试设备提出了更高的要求,希望提供一种功能全面、携带方便的小型化设备,用以满足试验的多种需求.为解决这个问题,研制了新一代时统设备——卫星授时控制器.基于GPS（全球定位系统）/BDS-Ⅱ（“北斗”二代）卫星授时原理,采用功能较强的微控制器和可编程器件产生多种时频信号、控制信号和模拟导航信息,实现了定时、控制、接收和产生等多重功能,提高了设备的集成性、通用性和便携性;同时采用倍频、锁相、驯服等技术,使设备10 MHz频率源的准确度提高2个量级,卫星同步精度优于50 ns.该控制器已成功应用于移动测控站和舰船试验中,效果良好.