中国低轨卫星星座组网设计与规划

针对全球性低轨卫星星座系统成本高、技术难度大、实现周期长等问题,提出了适 用于我国低轨卫星星座的分步实施方案。在分析星座设计主要问题的基础上,利用24颗卫星 设计了能够实现对中低纬度连续覆盖的低轨卫星星座,以此低轨星座构型为基础,结合我国 当前实际,在假定任务背景下,研究了第一阶段4颗卫星的优化部署方案,并利用STK对不同 设计方案的覆盖性能进行了仿真和对比分析,验证了连续覆盖型星座的优势,为我国低轨卫 星通信系统的组建提供了参考。     

基于分布式星群的双层星座设计

当前,陆地通信系统已无法满足日益复杂的信息需求,利用空间信息网络实现全球范围内的无缝覆盖和高效容量传输成为研究热点。现有卫星通信系统以单层星座为主,缺少高低轨卫星之间的协同。提出了一种基于分布式星群的双层星座设计,以基于分布式星群的低轨卫星作为网络架构的基础,采用星间链路实现低轨卫星之间的通信,通过高轨卫星实现中低纬度地区覆盖性能加强。仿真结果表明,所提方法在仅依靠在国内部署卫星地面站的前提下可实现全球多重覆盖。     

基于动态辐射源建模的低轨星座电磁发射评估系统设计

随着全球低轨星座系统蓬勃发展,不同星座系统卫星覆盖波束相互叠加,带来了频谱态势的复杂化,给其他系统带来了干扰隐患。传统的电磁频谱监视方案无法有效评估和高效表征低轨星座系统电磁辐射特性。为准确量化评估不同低轨星座卫星系统的电磁干扰,研究低轨星座卫星系统的电磁发射模型,结合轨道动力学研究电磁发射覆盖范围的动态分析方法,实现了低轨星座卫星电磁发射高效评估及可视化。     

低轨星座系统电磁发射可视化技术研究

针对国内外低轨卫星互联网的高速发展,O3b、OneWeb、starlink、Teleost、LEOsat等低轨互联网系统的逐步完善并覆盖全球,此时不同星座系统卫星覆盖波束相互叠加,带来了频谱态势的复杂化,给其他系统带来了干扰隐患。与此同时,随着各个星座系统的部署运营,地球所处电磁环境将变得复杂多变、电磁干扰情况发生的频次和程度更为严重。为准确量化评估低轨卫星系统的电磁干扰,本文通过研究低轨星座卫星系统的电磁发射模型,结合轨道运动学研究电磁发射覆盖范围的动态分析法,实现低轨星座卫星电磁发射的可视化。     

基于用户位置的低轨卫星波束关闭策略

由于多波束低轨卫星网络具有网络拓扑动态变化、高纬度地区存在波束重叠覆盖现象等特点,可能会引发严重的乒乓切换效应及大量的波束资源浪费.针对该问题,首先设计了卫星星座及多波束天线,建立了低轨卫星网络的覆盖模型,对卫星波束覆盖优化问题进行模拟和分析;其次,基于低轨卫星点波束覆盖、用户位置等约束,以最小化开启卫星波束为目标,提...     

面向低轨互联网星座的频率干扰仿真研究

低轨卫星互联网星座发展迅猛,使得空间频轨资源的受限情况越发严重,同频干扰分析问题值得重视。由于其具有规模大、动态性强、空间立体分布、波束体制灵活等特点,低轨卫星互联网星座系统之间的同频干扰场景与传统同频干扰场景有很大不同。文中针对低轨卫星互联网星座间干扰场景建立了统一的多波束分析模型。为评估实际卫星互联网系统的干扰影响,基于Matlab自动计算平台对Starlink星座和OneWeb星座间的下行通信频率干扰场景进行了仿真分析,结果表明低轨卫星互联网星座在大部分时间里会对其他同频星座造成严重干扰,引起通信质量的大幅下降。     

基于遗传算法的低轨天基雷达星座设计

从目标监视性能的角度出发,分析了低轨天基雷达星座的卫星总数、能量需求以及星座发射费用等优化目标。综合考虑了Walker星座的碰撞等约束问题,建立了低轨天基雷达星座设计的优化目标。提出了一种基于遗传算法的低轨天基雷达星座设计方法。根据天基雷达星座的特点,该算法在进化过程中使用了非可行解修正和约束分级等约束处理方法,有效提高了算法的运算效率。通过仿真实验验证了该方法能够有效的同时优化低轨天基雷达星座的构形和卫星参数。     

基于随机几何的低轨星座下行通信链路仿真与分析

低轨卫星网络具有低成本、大容量、广覆盖的特性,是未来空天地海一体化网络中的重要支柱和6G网络的关键组成部分,开展链路分析对于低轨星座链路设计与优化具有重要意义。由于低轨卫星移动性强、星地电磁环境复杂、链路较长等特点,星地信息传输与传统地面移动通信有着显著差异。根据低轨星座的特性构建星座网络的随机几何BPP模型,并针对低轨星座空间分布及移动特征,分析了单星及多星场景下的损耗、干扰等对星地通信链路的影响。通过给出星座系统干扰期望计算方法,并基于所构建BPP网络对星地通信链路特性进行仿真。仿真结果表明,构建随机几何的基于BPP分布的星座模型可以很好地模拟卫星网络的状态,采用随机几何对低轨星座下行通信链路进行仿真分析,能够得到更具泛化的星座构型下低轨星座对地面站的干扰情况,为巨型低轨星座网络分析及星地链路设计提供了参考。     

一种区域性覆盖星座设计与仿真方法

主要研究了对地面目标进行连续覆盖的星座设计问题。首先分析了星座最小仰角与星下点轨迹、轨道高度的关系,然后推导了对覆盖性能有重要影响的星间覆盖间隔时间和轨道面覆盖间隔时间的计算公式,提出理论算法与STK仿真相结合优化星座设计的方法,给出适合于中国的非静止轨道星座方案。仿真结果表明,该星座能对中国实施24h不间断覆盖通信。     

一种新型的低轨存储转发通信星座设计方法

针对低轨存储转发星座的特点以及传统星座设计方法无法同时优化覆盖性能和网络性能的不足,该文提出一种新型的兼顾覆盖性能以及网络性能的低轨存储转发星座设计方法,并采用非劣分层多目标进化算法(NSGA-II)优化该多目标多约束星座设计问题。通过基于STK和OPNET的协同优化仿真平台验证了该星座设计方法的有效性。     

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.     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

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.     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.