美军宽带卫星通信系统发展概况

本文主要介绍了美国军方目前正在使用和即将发射的几个军用宽带卫星通信系统．包括国防卫星通信（DSCS）系统、全球广播业务（GBS）系统、宽带全球卫星（WGS）系统、转型通信卫星（TSAT）系统及先进宽带系统（AWS）的发展概况。     

“转型通信卫星”取消之后——美军事卫星通信的新发展计划

在21世纪大大小小的军事行动中，带宽对作战人员来说将会与子弹同样重要，而转型卫星通信系统（TSAT）曾被认为是实现空中和海上优势的推动力和必要条件。现在，美国国防部取消了转型卫星通信系统计划，它将产生什么样的影响？带宽空缺将如何填补？这是美军在取消TSAT计划后必须考虑的现实问题，现在已有了答案。     

企业平台

波音演示TSAT系统一键启动式卫星地面站11月6日,美国波音公司及其转型卫星通信系统(TSAT)团队演示了一种一键启动式地面站。这种一键启动特性使得地面站技术人员或者远程指挥中心操作人员能够使用控     

美军转型卫星通信系统及其发展

为了跟上"新军事变革"的发展,适应"网络中心战"的要求,美军于21世纪初提出了"通信转型"发展战略。具体说来,就是实现"转型通信体系结构"(TCA)。TCA的目的是提供一套受保护的、类似互联网的安全通信系统,把太空、空气空间、地面及海洋的网络整合为一体,从根本上改善美军的通信能力。这一结构由转型卫星通信系统(TSAT)、全球信息栅格带宽扩展计划(GIG-BE)、战术级作战人员信息网(MN-T)和联合战术无线电系统(JTRS)等四大计划组成。美军认为,TSAT是TCA体系结构的主要推动力量,将发挥重要的组网和通信作用,将提供全球性、高带宽、高安全性、自动化及动态能力。虽然TSAT在2009财年被取消,但美军的信息化进程没有停步,而TSAT的很多思想依然体现在后续的军用卫星上。     

中小型计算机监测系统研究

介绍了计算机监测系统中应用到的一些先进技术．PLC技术、集散控制系统（DCS）、现场总线技术等．并结合各种技术的应用现状对比较分析了它们的优缺点．分析了监测系统的一般设计原则。在此基础上．提出了一种适合中小型监测系统的集散式计算机监测系统架构。     

基于卫星链路水上应急语音融合通信系统设计和实现

本文从目前水上应急通信现状和特点出发．设计了一套以VSAT卫星为链路．融合多种终端的语音通信系统．实现短波（渔业电台．对空电台,单边带）、超短波,Wi—Fi．手机．IP电话等互联互通．着重介绍了卫星链路构建．系统构成,各子模块设备构成及工作原理。     

全台网环境下江苏台播出系统建设全面告捷

为响应国家广电总局的号召．推进网络化数字化建设,江苏电视台作为《中国电视台数字化网络化建设白皮书（2006）、（2007）》的主要起草单位．提出了电视台进行台内资源整合、生产方式转型、业务流程再造的规范化思路,为江苏总台全台网及播出传送系统的建设提供了理论依据。在这一思路的指导下．江苏台播出系统建设取得了突破性进展,经过三个月的试运行．于近日顺利通过了项目系统验收．正式投入使用。     

基于固定电话网的证券交易系统方案设计

提出了一种基于固定电话网（PSTN）短消息的证券电子化系统．为了适应股票交易委托的需要，对PSTN的短消息系统进行系统和协议的扩展：这个系统增加了CTSI服务器的交易模块、业务交易网关和专业CP系统．这些扩展满足了股票交易的实时性．在保障交易安全的问题上，该系统采用了终端ID判别、3DES加密等一系列措施．文中详细介绍了该系统的框架、物理拓扑构、系统功能以及安全性设计．最后对该方案进行了详细的应用上的优缺点分析．     

网站内容推荐

RLM的快速物理设计 http：／／www．ednchina．com／0910-002．aspx 本文首先介绍IBM的专用集成电路（ASIC）设计流程．然后详细介绍层次化模块设计中对子模块进行快速物理设计的可重用设计流程（RLMREDOFLOW）．顶层整合时对子模块的优化处理方法．以及该RLM设计流程的优点。     

运营商“IP专用网络”设计要点

在IP技术发展定位转型的背景下,本文重点对运营商面向承载传统电信业务需求建设其“IP专用网络”的设计要点进行了介绍,其中主要涉及业务定位、层次结构、自治域（AS）组织原则、网络拓扑结构、业务／应用组织方式、QoS解决方案、业务承载及故障恢复解决方案、网络路由组织、应用系统接入解决方案等。此外,本文还对基于“IP专用网络”的移动增值应用承载方案进行了分析描述。希望能对相关网络、应用系统设计提供框架的参考思路。     

Subthreshold behaviour of e.s.f.i.-s.o.s. transistors

Theoretical and experimental results are presented which illustrate the influence of various parameters on the subthreshold behaviour of e.s.f.i.-s.o.s. transistors. The numerical analysis accounts for the thin silicon film and the existence of a second interface. A comparison is made with a corresponding bulk transistor, furthermore, between a two- and a one-dimensional analysis of e.s.f.i.-s.o.s. m.o.s.t. The agreement for real cases is found to be excellent.     

Current-kink noise of n-channel enhancement e.s.f.i.-m.o.s. s.o.s. transistors

An experimental study of the low-frequency-noise properties of n-channel epitaxial silicon films on insulator m.o.s. s.o.s. transistors has been performed. The measurements show an excessive noise contribution at drain voltages corresponding to the current-kink effect for temperatures ranging from 4.2 to 300 K.     

Noise behaviour of the m.o.s.f.e.t. at v.h.f. and u.h.f.

The optimum noise figures of an m.o.s.f.e.t. at u.h.f. and at pinch-off are calculated using a simplified equivalent circuit. The noise parameters are also determined experimentally. Theory and experiment are shown to be in good agreement. Noise parameters of the m.o.s.f.e.t. for the frequency range 0.1?0.8 GHz are given.     

Performance of GaAs power m.e.s.f.e.t.s

Power performance results at 4 GHz are summarised for GaAs m.e.s.f.e.t.s ranging in size from 4 to 16 mm gate periphery. A double-chip 16 mm unit operated at 24 V source-drain bias produced 13.5 W with 3 dB gain and 10.7 W with 8.1 dB gain. Although lack of perfect power and gain scaling is observed, the degradation in output power of the 16 mm devices was only 1 dB compared to the smaller devices.     

Conversion gain of m.e.s.f.e.t. drain mixers

A theoretical analysis of the gain properties of m.e.s.f.e.t. drain mixers is presented. The m.e.s.f.e.t. model includes the nonlinearity of both the transconductance and the drain resistance. For a special case, a simple analytical expression for the gain is given. Numerical results for a typical example are briefly presented as an illustration.     

Analytical realisation of e.v.c.-a.r.c. networks

Consideration is given to the complete analytic solution of 3rd-order equal-valued-capacitor RC (e.v.c.-a.r.c.) networks due to Dutta Roy and Malik, and realisability limits are derived. The practically desirable cases of minimum resistor sum and minimum resistor spread are shown to occur at the same value of amplifier gain.     

Efficient algorithm for determination of a.r. part of a.r.m.a. model

A fast recursive scheme is given for the solution of the Yule-Walker equations to obtain the a.r. part of an a.r.m.a. model. A lattice equivalent to the predictive filter is also included. This new structure requires what is subsequently called an adjoint model. The algorithm can be used in the evaluation of the a.r. and m.a. parsimonious orders.     

Substrate dependence of InP m.e.s.f.e.t. performance

There is evidence to suggest that Fe outdiffuses, during the growth, into the epitaxial films prepared by vapour-phase epitaxy at 650°C. Field-effect transistors on Fe-doped material show substantial looping that was absent on Cr-doped material and exhibit about 2 dB worse noise figure at about 7 GHz. Experiments with low 1015 S-doped InP grown on Sn-, Cr- and Fe-doped substates indicate that such outdiffusion is typically about 5 ?m. Saturation velocity levels in the m.e.s.f.e.t. channel are about 1.7 × 107 cm/s and 1.3 × 107 cm/s, associated with Cr and Fe doped substrates, respectively.     

On-resistance of V-v.m.o.s. power transistors

An expression for the on-resistance of a V-groove vertical-channel m.o.s. (V-v.m.o.s.) transistor is presented. The expression relates the on-resistance to the geometry and resistivity of the drain drift region and is useful in optimising the drift region parameters for minimum on-resistance and maximum drain-source breakdown.     

New structure of enhancement-mode GaAs microwave m.o.s.f.e.t.

This letter proposes a new feasible device structure of an enhancement-mode GaAs deep-depletion m.o.s.f.e.t. as an attractive alternative to the junction-gate f.e.t.s and describes its microwave properties. The device has been fabricated on a high-resistance epitaxial n?-layer by simple readily available technology without requiring the sophisticated control of the channel thickness needed for the conventional junction-gate f.e.t.s. The 'normally-off nature of the device can be explained on the basis of the substrate space-charge region extending over then?-layer. The microwave performance of the device can be favourably compared with that of currently achievable junction-gate normally-off f.e.t.s. Unilateral gain drops to zero at a frequency slightly above 7 GHz.