Digital visions: where the superhighway will lead

The author looks forward to the world of interactivity made possible entirely by digital communications, storage and compression. Digital technology has also expanded the capacity of communications networks, supporting an enormous rate of growth in traffic. Compression has immediate transmission cost benefits for satellite broadcasters, since an analogue PAL transponder covering Europe, say, may cost £4 million per year. A compressed 8 Mbit/s digital service (Filmnet), with four digital channels per transponder, quarters the cost per programme service. For a 2 Mbit/s digital service, costs could fall to around £250 000 per year. As the cost of compression equipment falls, many more services can be delivered direct to homes by satellite or cable systems     

A Method for Transponder Capacity and Link Performance Optimization in Preassigned Multilevel SCPC Systems

An investigation of ways to improve the capacity in a dedicated SCPC transponder has resulted in the development of a method for optimizing the transponder capacity and link performance in preassigned multilevel SCPC systems. The main approach is to form different groups of carriers based on the traffic requirement, and on typical characteristics of the link destinations such as variations in the satellite e.i.r.p. and downlink path loss, and differences in the receive earth station antenna size. The Fletcher-Powell optimization technique is used to determine the set of optimum carrier levels at the transponder TWTA input. Application of the method to a number of preassigned multilevel frequency plans in a global transponder environment clearly indicates that the total carrier-to-noise ratios for all the links can be optimized at any specified CNR value, and that the optimized capacities are substantially higher than that of the basic two-level system. The implementation of multilevel plans is fairly simple if all downlink carrier levels can be monitored at some reference station in the SCPC network to reasonably control the uplink e.i.r.p. levels.     

Dual Video Signals per Transponder for Satellite News Gathering

Transmission of the video signals through a single satellite transponder in a Satellite News Gathering environment is complicated by the short duration of the broadcast feed, large number of uplink sites sequentially. accessing the satellite, equipment cost constraints, and small transmit antenna size. Two impairments to dual video operations are transponder power sharing and the phenomena known as chrominance crosstalk, where the chrominance information of one carrier is superimposed on the other. While several methods have been proposed to reduce the effects of the chrominance crosstalk, no universally applicable, simple solution exists to date.     

基于扩频多址的差转游标测距方法与应用

针对游标测距法在转发测距中无法实现多址测距的问题,提出了一种基于扩频多址的差转游标测距方法。该方法采用游标法实现高精度测距,采用直接序列扩频技术以正交的伪随机码（PN码）区分不同的测距信号,利用不同的差转频率区分不同的转发信标。基于该方法构建了测距系统,系统的测距精度可达亚米级。转发信标使用电池供电和无线通信调度,结构简单,成本低,功耗小,安装简单。该系统非常适用于工业场景的人员定位管理。     

一种基于机器学习的卫星重叠隐蔽通信方法

针对传统卫星重叠通信中单个掩护信号带宽以及功率容限不够的问题,利用卫星转发器频谱环境中多个掩护信号提出了一种频域分割-子谱功率控制联合优化的多掩护信号重叠通信方法,建立了隐蔽通信信号传输性能和隐蔽性能的双目标优化问题,信关站侧采用感知的历史频谱数据训练生成支持向量机回归预测模型,用来预测不同转发器频谱环境下隐蔽信号的通信性能和隐蔽性能,并将训练好的预测模型下载到通信终端;终端侧利用双目标背包算法将支持向量机回归预测模型预测的隐蔽信号的通信性能和隐蔽性能作为价值因素、掩护信号个数作为背包重量来选择转发器频谱环境中的掩护信号,并且求解出隐蔽信号的频域分割和子频谱的功率控制参数,从而实现终端通信信号隐藏在卫星转发器的频谱环境中的目的。     

S频段联试应答机的改进设计

针对S频段联试应答机提出了接收和发射频综共用的改进设计方案,对改进后的应答机频率关系、组合干扰、信号处理单元以及信道单元设计进行了分析、仿真和测试,结果表明其功能和性能指标满足S频段测控系统的系统联试要求.该设计在满足接收和发射载波频率相干转发比的同时节省了一个频综,同以往的S频段联试应答机相比具有硬件电路简单、成本低、可靠性更高的优点.     

Companded single sideband (CSSB) AM/FDMA Performance

The continuing need for increased traffic capacity for telephony over satellite links combined with the availability of low cost and accurate LSI compander chips has caused renewed interest in SSB satellite transmission using companders to reduce the impairments caused by thermal noise, interference and intermodulation encountered on the transmission link. This type of transmission is designated as CSSB/AM and may be operated in a multicarrier per transponder (FDMA) manner. The capacity achieved is a function of the average power during the occurrence of speech and because this value has decreased in modern telephone systems, the advantages to be gained from CSSB/AM are increased. This paper presents the development of expressions for channel capacity of CSSB/AM links as a function of carrier-to-noise ratio and speech power level while active. These are used to estimate the capacity achievable in an INTELSAT IV type transponder.     

Generalized satellite link model and its application to the transmission plan

A generalized model for the satellite link that includes non-linear effects is presented. The transponder is handled as a black box with nominal gain g_s. At a specific operating point each signal in the transponder has its own gain, g_sci, that may be different from g_s. The parameter g_sci depends on the operating point of the transponder, the power of the signal and the distribution of the residual transponder power among the other carriers. The intermodulation between the carriers and between them and the up-link noise is included in the model as well. The generalized model is represented by the conventional traditional equation, modified with correction factors which account for the nonlinear effects. Application of the model to typical transmission plans is given and comparison of the results to field experiments and transponder analysis program is included. Emphasis is placed on the use of the transponder with mixed TV and SCPC operation.     

全频带适应统一应答机的设计

本文论述了Ｓ频段地面测控站全频带适应统一应答机的设计特点，提出了全频带相参应答机的设计思想，该机具有测距，测速，解，调遥控指令副载波和发射遥测副载波的功能，在Ｓ频段带宽大于１００ＭＨｚ的情况下满足地面测控站的标校和联试要求。     

遗传算法在载波排列优化中的应用研究

卫星转发器的固态放大器(Solid State Power Amplifier,SSPA)或行波管放大器(Traveling Wave Tube Amplifier,TWTA)产生的非线性互调噪声会对有用载波进行干扰。为了使非线性互调噪声对有用载波的干扰最小,提高卫星通信质量,提出了基于遗传算法的载波排列优化方法。简述了遗传算法原理,分析了载波排列优化的基本原则,阐述了该方法的实施步骤,进行了仿真实验,同时分析了载波排列规律。     

某型空管应答机高度源模拟器电路设计

介绍了基于FPGA的某型空管应答机高度源信号模拟器的电路设计过程,主要包括飞机高度数据的编码和格式、系统硬件结构和工作流程以及FPGA功能模块设计和VHDL编程实现等,并通过了Active HDL 6.1的仿真验证。提出的数据转换算法节约了FPGA芯片资源,转换速度快,延时小。系统功能改进和升级十分方便,稳定性好、可靠性高、成本低廉。     

Architectures,protocols and design for highly dynamic optical networks

In order for dynamic optical networks to be commercially viable, it will be essential to have signaling protocols that can establish connections quickly and minimize the use of transponders for wavelength conversion and regeneration. Rough estimates indicate that in dynamic optical networks, transponders will comprise a significant component (e.g., 60%–70%) of the cost of the optical networking infrastructure. A key performance metric in dynamic networks is the connection blocking probability, and therefore a dynamic optical network infrastructure must be designed to meet stringent blocking requirements (e.g., <10^?3 blocking probability). A key element in achieving that blocking objective is the ability to design the network to support shared transponder pools at selected network nodes, and have the capability to efficiently size those transponder pools to meet the required blocking probabilities. This paper addresses how to size shared transponder pools once the nodes that support those pools have been determined. The methodology can efficiently design for very small transponder-related blocking probability (e.g., <10^?4) by using simple, straightforward simulation and analysis techniques. We also describe a 3-Way-Handshake (3WHS) signaling protocol that can quickly set up connections (e.g., in <100 ms) and identify available resources (available wavelengths, transponders) so the connection setup process minimizes the use of transponders.     

设备时延测量的新方法

讨论了连续波转发器设备时延 (距离零值 )测量技术 ,重点研究了利用测量副载波调制边带侧音相位完成中频调制转发应答机绝对距离零值测量的工作原理 ,并介绍了适用于各种形式应答机(包含中频调制转发应答机 )的距离零值通用测量方法 ,分析了测量方法误差。     

通信卫星Ka波段转发器技术的研究

本文论述了通信卫星Ｋａ波段转发器的实现方案及技术途径，介绍了国外典型的几个通信卫星Ｋａ波段转发器的研制设计情况，提出了我国研制通信卫星Ｋａ波段转发器的建议方案。     

Ku波段通信卫星模拟转发器设计中的关键问题

转发器是通信卫星中的通信分系统,是通信卫星的核心。模拟转发器作为通信卫星转发器地面测试的专用设备,主要用于模拟该转发器的频率关系及电平关系。在介绍转发器的结构、特点的基础上,对转发器噪声系数、增益分配、电磁兼容等转发器设计中的关键问题进行分析,并给出某一采用一次变频体制方案的Ku波段模拟转发器的系统实现方法。最后得到系统测试结果,证明了设计的可行性和可靠性。     

基于无源标签的远距离射频识别系统

通过RFID阅读器将标签对标签中的信息进行收集,然后将信息传送到操作应用系统中去,从而得知标签内容。虽然有源标签的传输距离要大于无源标签,但是考虑到设计成本及系统的广泛使用,于是文中通过标签依靠阅读器发送过来的载波将存储的信息发送到阅读器,再由内嵌在阅读器中的ZigBee,传送给作为协调器的ZigBee模块后送往应用系统中去,通过无源RFID和ZigBee来建立远距离的模型,达到扩大射频覆盖范围的功能。     

近地卫星GPS接收机降级应用

针对 GPS 接收机发生 SEL 事件后的温度升高问题,在卫星轨道漂移分析基础上, 重点考察卫星应答机的 AGC 电压与载波锁定的温度敏感特性,并确定载波锁定的温度上限,进而提出 GPS 接收机的降级应用方案,关闭轨道电路板。结果表明,应答机载波锁定时的 AGC 电压应在 0.82V 以下,对应卫星应答机温度不超过 26.2°C;轨道电路板断电后,GPS 接收机定位与守时功能正常,工作温度在 20.5°C 以下,发生 SEL 事件的概率降低;GPS 接收机温度对于卫星应答机的影响明显减弱,应答机在原有上行约束下的载波锁定时长优于 150s,满足上行遥控注入时限需求。降级应用方案已施行于大数量卫星集中监控与管理。     

一种在一体化TCAS系统中通信编解码的实现方法

当前的飞机防撞系统是由TCAS和S模式应答机两个独立的子系统及其附属设备构成,这种结构给飞机的空间造成了极大的浪费,使得设计成本大大增加,同时庞大的体积也限制了TCAS在军事方面的应用。为解决这一问题,本文引入了一体化TCAS系统的概念,并设计了一体化TCAS系统中的通信编解码,给出了实验结果。     

Earth-station size Vs. Error-correction coding in the design of ku-band satellite communications systems

A Ku-band satellite transponder capacity is evaluated for a PCM/QPSK/FDMA system in which many carriers are transmitted in an SCPC mode. The capacity depends on earth-station sizes, error-correction coding, required signal-to-noise ratio and required availability in rain; for simplicity all of these parameters are assumed to be the same for all carriers in the transponder. A method of accounting for the effects of rain is developed; it is assumed that the earth-stations do not adjust their output power when it rains. Trade-offs between earth-station sizes and error-correction code rates are examined.     

有源转发器延时对SAR定标测量的影响

该文研究了有源转发器延时对距离向压缩信号、方位向压缩信号幅度和相位的影响;通过数据仿真,分析和讨论了不同分辨率、不同时延长度的情况下,有源转发器延时对点目标成像位置、主瓣及旁瓣的影响,并给出有源转发器时延设置时需要考虑的因素。