低轨红外预警星座无源定位精度分析

建立了低轨红外预警星座的三维成像观测模型,分析了多测量因素条件下低轨红外预警星座的无源定位精度,研究了不同星座布局条件下像平面测量误差、卫星位置测量误差以及欧拉角测量误差等因素对定位精度的影响。仿真实验表明,本文的定位精度分析方法能够有效分析低轨红外预警星座的定位精度。从仿真实验结果得到了一些可用于低轨红外预警星座设计和传感器调度的指导性结论。     

面向通导共生的低轨卫星机会信号定位管理

通导共生是指通信和导航信号共存于卫星生态环境中。针对定位或通信的单一功能低轨卫星星座,在定位或通信信号不可用时难以快速进行定位管理的难题,提出了应用扩展卡尔曼滤波器算法,对低轨卫星通导共生星座的机会信号进行定位解算,突破定位管理对单一导航系统的依赖。首先,介绍了卡尔曼滤波的基本原理,结合低轨卫星多星座定位管理算法,提出了一种基于机会信号的卡尔曼滤波定位管理算法;其次,分析了所提算法的优点,包括提高定位精度、提高定位效率、提高定位稳定性等;最后,进行了实验,验证了所提算法的有效性。结果表明,所提算法能够有效地提高定位精度、定位效率、定位稳定性,为低轨卫星通导共生星座定位管理提供了一种有效的解决方案。     

基于星间激光测距的高轨卫星定位技术研究

针对传统的高轨卫星定位技术存在定位精度低的问题,提出了基于基于星间激光测距的高轨卫星定位技术。在高轨卫星飞行器上安装低噪声激光探测器,借助激光探测器、发射机以及接收器构建星间通信链路,分析接收天线的接收功率与发射天线的发射功率之间的关系,通过激光脉冲传输空间测距与高轨卫星信号捕获接收功率和发射功率获得定位初始数据;再分析星间相对运动和修正电离层误差,得到定位数据的精确解算融合结果。选取精度因子DOP作为评判高轨卫星定位技术的参数,通过仿真实验发现高轨卫星定位技术比传统定位技术的平均DOP值高2.89,由此证明所提定位技术的定位精度更高。     

影响卫星导航定位系统精度的关键技术

对影响导航定位系统定位精度的各种因素进行了分析。研究了影响导航定位精度的关键技术问题,如时间基准、时间同步和卫星定轨等。叙述了GPS系统的时间基准精度的国内外技术水平,以及时间同步的各种常用方法,如单向时间传递、共视时间传递和双向时间传递等。描述了影响卫星定轨的各种因素,特别是地球重力、月球引力、宇宙引力、大气阻力和阳光光压等对卫星轨道的作用。指明了卫星导航系统的主要误差源或影响定位精度的主要因素。     

星载GPS辅助低轨卫星运动学定轨方法综述

本文简要介绍了星载GPS低轨卫星定轨的背景、系统组成和主要定轨方法。重点论述了星载GPS低轨卫星运动学定轨的基本原理及方法,指出了各种运动学定轨方法的优点和不足。分析了各种运动学定轨解算的特点,并对星载GPS低轨卫星运动学定轨的发展方向进行了展望。     

地面基准站网与星载GNSS融合的高中低轨卫星联合精密定轨

下一代导航系统拟纳入低轨卫星（LEO）作为增强和备份。研究了地面基准站网与星载GNSS融合的高中低轨卫星联合精密定轨（POD）理论与方法，基于实测国际地面站（IGS）和低轨卫星星载GNSS数据，通过建立高精度动力学模型和观测模型，根据全球测站和区域测站两种情况进行了导航星与低轨星的联合精密定轨试验。结果表明，联合定轨可同时获得导航星和低轨星厘米级的定轨精度。低轨星作为高动态天基测站，对导航星定轨精度的提升程度可达20%~90%。     

面向低轨通信星座的导航定位方法比对研究

当前基于低轨卫星的导航定位方法研究成为国内外热点,其中基于低轨通信卫星的导航定位技术更是当前研究的重点方向。然而低轨通信星座较低的时空基准精度给导航定位带来了较大的挑战,针对弱时空基准约束的低轨卫星导航定位体制设计还处在研究的初级阶段。本文针对低轨通信星座的导航定位服务需求,基于LEO通信卫星的伪码测距信号与多普勒测频信号,开展精度因子（Dilution of Precision,DOP）及定位精度均方根误差（Root Mean Square Error,RMSE）分析,并对两类测量体制下的低轨通信星座导航定位服务性能进行分析论证。理论分析与仿真结果表明,在设定低轨通信卫星10 m～30 m弱时空基准误差的约束下,多普勒测频体制具有更优的导航定位精度,其周期平滑后的三维RMSE值为1.28 m,相比伪码测距体制下的三维RMSE值优化了86.8%;二维RMSE值为0.99 m,相比于伪码测距体制提升了52.9%。本文提出了一种较为可靠的低轨通信星座多普勒定位方案,为未来低轨通信卫星用于导航定位服务提供了有益参考。     

基于EPFD分析的高低轨卫星角度间隔研究

随着低轨(LEO)通信卫星业务需求的增加，低轨卫星需要使用Ka频段进行通信。本文针对低轨卫星采用Ka频段可能与在轨的高轨卫星发生同频干扰问题，采用基于链路分离角的空域分隔方法进行干扰规避的角度间隔分析。分别从不同干扰场景、地面站分布情况来分析对干扰角度间隔的影响，并在此基础上提出该角度间隔范围内，低轨卫星需采取的干扰规避措施。     

低轨卫星互联网：发展、应用及新技术展望

传统以人为中心的通信模式正在逐步向以服务为中心的通信模式转移，未来的6G时代，将是空天地海一体化的泛在网络。为了解决互联网的“最后一公里”问题、实现全球无差别的信息覆盖，低轨卫星互联网应运而生。从互联网的概念入手，介绍了低轨卫星的发展，并由此衍生出低轨卫星互联网的概念；概述了国内外在低轨卫星互联网建设中的项目进展情况；详细阐述了低轨卫星互联网在陆地、海洋及空中的典型应用场景和业务接入需求；梳理了低轨互联网发展过程中面向用户的4个关键技术，即抗干扰技术、感-传-算一体化技术、多星多波束联合传输技术和免授权接入技术，希望对低轨卫星互联网的工程推广产生一定的积极意义。     

面向低轨卫星网络的组网关键技术综述

随着信息通信技术的不断发展，人类对于扩大网络覆盖范围和降低通信时延的要求越来越高。低轨卫星网络是一种利用轨道高度较低的卫星构建的网络体系，具有覆盖范围广、通信时延低等优势。基于此，首先概述了低轨卫星网络的国内外发展现状及其组网所面临的挑战，进一步阐述了低轨卫星网络组网关键技术难点及建议，最后结合分布式、博弈论和人工智能等方法，对潜在可行的低轨卫星组网方案进行了探讨。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working.     

Call for Papers

正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks