大跨度天基数据链的TDD时隙调度分析与优化

针对天基数据链系统卫星间的传播时延较大且节点间距离变化较大等特点，提出了一种提高时频资源利用率、提升系统容量、减小时延的方法。在时分多址与空分多址相结合的接入方式下，进行了时隙调度的分析与优化，利用卫星星座的空间复用与大跨度传播时延特性，采用时隙编排、收发状态调整、帧格式优化等手段，将信道利用率和系统容量提升了1倍，将卫星节点在某一方向获得服务的平均等待时间缩短为原来的1/4，提高了天基数据链系统的服务质量。     

罗兰C数据调制技术研究

罗兰C数据链已成为罗兰C系统扩展应用的重要方向，它不仅可以广播卫星导航的差分和完善性信息，而且也可在罗兰C差分和星基，陆基综合导航中应用．本文对罗兰C数据链的调制技术进行了论述，分析了附加调制对罗兰系统的影响，并介绍了调制的实现方法．     

经典Link数据链信道传输模型及特性研究

随着生活节奏不断加快，对通信信息的实时接收要求越来越高，需要各类信息能够快速传递，各个工作节点单元信息的共享、协作、同步已经逐渐成为成功与否的关键因素，而实现这一功能的数据链系统整体性能主要取决于其信道传输的性能。文中主要针对数据链技术中信息传输通道的性能进行研究，给出直接影响整个数据链系统性能的因素，并利用OPNET对Link-16数据链进行传输建模，采用无线信道连接的方式，设计了各种数据链通信环境以检验其性能指标，网络中每个节点的调制方式、带宽、码元传输速率、工作频段设置符合经典Link数据链的标准。仿真结果展示了信道传输的平均延时、错误数据、有效数据和接入节点随时间变化的情况，并给出调制方式对数据量丢包率、平均延时等数据链信道传输性能的影响结果，研究结论对数据链应用的发展具有一定的借鉴意义。     

无人蜂群分布式相干协作通信系统

为了解决无人（UAV）蜂群数据链系统受机载端发射功率及天线口径限制，空地通信距离受限的问题，提出了一种分布式相干协作通信系统的设计方法。基于信道反馈的校正补偿信息，蜂群节点可同时发送通信信号，在地面节点处实现相干协作信号增强。在实验室内搭建原型测试系统，通过理论分析和实测对比，验证了多节点相干协作传输的通信能力。4节点协作时，相干协作能力实测可增加10.58 dB。该方法使得在保持无人蜂群数据链端机及全向天线不变基础上，实现通信距离扩展、抗干扰能力提升变得可行。     

罗兰C组合导航系统的设计与实现

罗兰C数据链已成为罗兰C系统扩展应用的重要方向，它不仅可以广播卫星导航的差分和完善性信息，而且也可在罗兰C差分和星基／陆基综合导航中应用。本文对罗兰C数据链技术在组合导航试验系统中的应用进行了论述，并介绍了“信息发播”功能的实现方法。     

基于星间测距的卫星自主定轨研究与仿真

提出了一种利用星间距离信息和扩展卡尔曼滤波算法确定卫星的位置和速度的方法。利用STK软件建立GPS星座,将1颗目标卫星与3颗参考卫星之间的距离引入一定的误差作为星间观测值,利用扩展卡尔曼滤波算法实现卫星的自主定轨。并对算法进行了改进,利用几何准确度因子GDOP值控制参考卫星的选择,消除了误差峰值。运算结果表明改进后的算法有很好的收敛性,提高了定轨准确度。     

卫星数据链-卫星通信应用的新领域

卫星数据链作为卫星通信的一种新型应用,越来越引起各国的重视。首先介绍了 数据链在现代战争的地位和作用,以及几种传统的无线数据链;然后针对英国、美国开发卫星 数据链进展情况进行了详细的介绍和简单的分析,最后提出利用卫星数据链构建一体化数据 链的构想。     

基于卫星移动通信的网络移动研究

文中研究了利用卫星移动通信支持网络移动的必要性,提出了利用卫星移动通信网扩展地面IP网覆盖范围的设想和实现方案,分析了该方案的特点及需要解决的关键技术问题,重点分析了卫星移动信道对TCP/IP协议的影响及网络移动过程中的连接和路由选择问题,卫星移动信道误码率、往返时延、变化率、信道不对称性及信道频繁通断对TCP/IP协议工作效率的影响,以及提供网络移动应解决的双重隧道问题。     

转发式干扰下卫星数据链效能分析与仿真

针对无人机上卫星数据链的实际应用情况,研究了卫星数据链的常用抗干扰措施,分析了各抗干扰措施的弱点及对抗策略,提出采用相关性干扰对抗卫星数据链,构建了基于时延的转发式干扰模型,对转发式干扰下的卫星数据链效能进行了分析和仿真。仿真结果显示,该方法能够有效对抗卫星数据链,具有一定的可行性。     

基于HARQ机制的数据链通信性能分析

利用JTIDS数据链现有的编码体制提出了一种基于HARQ机制的数据链通信模式,以提高报文传输的可靠性.首先对JTIDS系统的时隙结构进行改进,建立了HARQ机制的反馈信道,以保证该通信模式的实现;然后分析了JTIDS数据链系统在莱斯信道环境下的符号误码率,并在此基础上采用Markov模型对基于HARQ机制的数据链通信模式进行性能分析,评估了在该机制下通信的吞叶量、报文到达率、报文服务率和报文传输服务时延;最后,利用GSPN网对基于HARQ机制的数据链通信模式进行仿真分析,仿真结果表明采用HARQ机制的数据链通信系统能够很好地改善在恶劣信道环境下的报文传输能力,提高报文传输的可靠性.     

Suppression of torsional oscillations in a high-performance speedservo drive

This paper deals with the problem of mechanical resonance in modern servo drive systems having the speed control loop bandwidth and resonance frequency above 100 Hz. To enable the extension of the range of stable gains in the presence of flexible coupling, a simple and straightforward modification of the speed loop controller is proposed in order to augment the performance of present speed controllers and to make them accordant with mechanical structure suffering from the compliance problem. This paper is comprised of the analytical considerations, straightforward design guidelines, and results of experimental verification obtained by an experimental setup with the elastically coupled 7-N m synchronous servo motor and mechanical resonance frequency of 160 Hz     

基于静态链表SCPI解析系统设计

针对传统的SCPI解释方式占用过多内存,制约了在嵌入式系统上的应用,文中设计了一种方便移植和扩展的SCPI语言解析方法。该种方法用静态链表的结构来保存SCPI命令集,通过这种方法建立的SCPI解析模块,占用内存少,且方便移植和扩展。利用文中方法设计的SCPI解析模块可方便应于各种智能程控仪器,并适用在嵌入式系统下工作。     

Multifrequency version of pseudodiagonalisation

An extension of the pseudodiagonalisation technique leads to a minimisation of the off-diagonal terms of the inverse Nyquist array in a way which reflects dominance over an entire frequency range. This new formulation also permits the design of certain types of dynamic compensation for multivariable control systems.     

Birnbaum's measure of component importance for noncoherent systems

Importance analysis of noncoherent systems is limited, and is generally inaccurate because all measures of importance that have been developed are strictly for coherent analysis. This paper considers the probabilistic measure of component importance developed by Birnbaum (1969). An extension of this measure is proposed which enables noncoherent importance analysis. As a result of the proposed extension the average number of system failures in a given interval for noncoherent systems can be calculated more efficiently. Furthermore, because Birnbaum's measure of component importance is central to many other measures of importance; its extension should make the derivation of other measures possible.     

Constraint analysis for extended dynamic fault tree

As a new extension of dynamic fault trees,time delay gate was proposed.This new mechanism can be used to model the time delay on the fault propagation from the lower level subsystems to the higher level system.The dynamic Bayesian networks was extend to solve the dynamic fault trees containing time delay gates.An algorithm based on SMT to support the optimized failure distribution under the nondeterministic range constraint of basic events was also proposed.The effectiveness is shown by comparison with existing tools on analyzing and solving real systems,and the effects of range constraints and gate parameter on the failure distribution of systems is illustrated.     

混沌在数字通信中的应用

随着对混沌理论的深入研究,混沌具有的优良特性必然被人们所认识,并应用到实际工程中来。短短十几年,混沌通信系统得到了充分的发展,目前正从理论分析向实用化转变。混沌通信系统是传统通信系统的扩展,同样可以分为相干通信和非相干通信两大类。文中着重对相干、非相干混沌数字通信系统进行介绍和评价,指出混沌数字通信系统亟待解决的若干问题,最后对混沌在传统通信系统中应用的前景进行了展望。     

Common principles of image acquisition systems and biologicalvision

In this paper we argue that biological vision and electronic image acquisition share common principles despite their vastly different implementations. These shared principles are based on the need to acquire a common set of input stimuli as well as the need to generalize from the acquired images. Two related principles are discussed in detail, namely, multiple parallel image representations and the use of dedicated local memory in various stages of acquisition and processing. We review relevant literature in visual neuroscience and image systems engineering to support our argument. Particularly, the paper discusses multiple capture image acquisition, with applications such as dynamic range, field-of-view, or depth-of-field extension. Finally, as an example, a novel multiple-capture-single-image complementary metal-oxide-semiconductor sensor is presented. This sensor illustrates the principles that are shared among biological vision and image acquisition     

Extended Virtual Boundary and Its Application in Dynamic Spectrum Allocation

This paper presents an efficient dynamic spectrum allocation （DSA） scheme in a flexible spectrum licensing environment where multiple networks coexist and interfere with each other. In particular, an extension of virtual boundary concept in DSA is proposed, which is spectrally efficient than the previous virtual boundary concept applied to donor systems only. Here, the same technique is applied to both donor and rental systems so as to further reduce the occurrences where the insertion of guard bands is obligatory and as a result provides better spectral efficiency. The proposed extension improves the spectrum utilization without any compromise on interference and fairness issues.