双层等离子体对6 GHz高功率微波防护实验

针对高功率微波对电子设备的安全威胁,设计了一种双层柱状等离子体阵列对高功率微波进行防护。其中单根等离子体柱的直径为25.4 mm,长度为600 mm,等离子体频率与碰撞频率可进行控制。利用搭建的实验测量系统,研究了微波极化方向、等离子体电子密度、放电单元层数等因素对高功率微波透射衰减的影响。实验结果表明:当高功率微波未激发等离子体产生非线性效应时,TM极化时的防护效果优于TE极化时的防护效果,且能量衰减分别可达20.9 dB和14.7 dB;随等离子体电子密度增大,微波透射功率减小,防护效果增强;由于层间反射作用,双层等离子体对高功率微波的透射衰减远大于单层等离子体衰减值的两倍。     

小型化高功率微波限幅器研究

电子装备现已被大量应用,在如此复杂的电磁环境下高功率微波可导致接收机灵敏度下降甚至失效。为了满足高功率微波的防护需求,介绍了一种基于PIN 二极管的小型化高功率微波限幅器,体积为34 mm×Φ9 mm。测试结果表明,在0.3~2 GHz 频带内,该限幅器实现了小信号插损小于1 dB,输入输出驻波比小于1.5;可承受脉宽100 μs,占空比0.1%,峰值功率超过1000 W,漏功率小于17 dBm。国内外尚无类似指标限幅器相关报导。该高功率微波限幅器体积小、频带宽、耐功率高,可大大提高接收机可靠性,具有广阔的应用前景。     

电磁波在均匀磁化等离子体中的衰减与反射

等离子体覆盖住金属导体,通过等离子体对入射电磁波的折射、吸收,使得入射波功率衰减,降低了反射功率,起到减小目标RCS的作用.对于均匀磁化等离子体,针对介电常数与等离子体粒子密度、外加磁场强度、电子碰撞频率以及入射波频率的关系,仿真计算了不同的等离子体粒子密度、外加磁场强度、电子碰撞频率以及不同等离子体厚度在毫米波波段对电磁波的衰减和反射特性的影响.     

频率对PIN限幅器微波脉冲热损毁效应的影响

采用数值仿真和理论分析相结合的方法研究了频率对PIN（positive-intrinsic-negative）限幅器微波脉冲热损毁效应的影响.研究发现,在相同脉冲宽度情况下,PIN限幅器微波脉冲热损毁功率阈值随频率的升高而降低,由于在一定功率下虽然频率与微波脉冲能量无关,但是在相同脉冲宽度情况下,PIN管阻抗周期性增大的次数随着频率的升高而增多,使得PIN管平均阻抗增大,实际吸收能量增多.该规律对全面评估PIN限幅器的微波脉冲防护能力具有重要的意义.     

110 GHz高功率微波在大气击穿等离子体中的传输、反射和吸收

高功率微波极易引起大气击穿, 而伴随产生的等离子体将对微波传播特性产生很大的影响.基于电子流体模型, 研究了一个大气压下110 GHz高功率微波在大气击穿等离子体中的传输、反射和吸收特性.模拟结果表明, 大气击穿等离子体结构在空间呈丝状分布, 其与实验现象符合得很好; 由于大气击穿等离子体是时变的, 其对微波的反射和吸收也是时变的; 随着时间的推移, 等离子体吸收功率逐渐增加直至达到饱和水平, 且其远大于微波反射功率; 当减小入射电场时, 等离子体对微波的反射变得更低.将110 GHz微波击穿阈值的模拟结果与实验数据进行对比, 发现两者吻合得很好.     

一种改进型的高功率限幅器

通过对pin限幅器的工作原理进行理论分析,引入了微波功率限幅器功率容量的计算方法,并以此为基础进行了微波功率限幅器设计。这里讨论了一种实用的高功率限幅器,它采用多个限幅二极管并联的方式,有效提高了限幅器的抗烧毁特性,从而提高限幅器的高功率通过能力;并且通过外加耦合器对限幅二极管施加正偏压的电路方式,有效提高了限幅器的最高承受功率。通过一个L波段脉冲500 W的高功率限幅器的实际设计和制作,对上述限幅器原理和方法进行了验证,取得了良好的结果。     

半导体电磁防护限幅器的发展

当前电磁环境日趋复杂,超宽带、高功率等强电磁技术已经成熟,对信息化装备构成了越来越严重的威胁,限幅器的应用需求越发迫切。文章从半导体限幅器的防护原理及电路结构入手,结合电磁脉冲防护及高功率微波防护的典型应用,详细介绍了电磁防护限幅器的技术路线,对比了Si、GaAs限幅器的特性,指出兼具Si及GaAs限幅器优势的高频、低插损、耐高功率GaN限幅器将是未来电磁防护限幅器的发展趋势。     

微波谐振腔测量气体激光器电子密度

微波谐振腔方法广泛地用来测量气体激光器的电子密度.当等离子体置入微波腔后,由于放电等离子体对微波腔频率的微扰,引起谐振腔共振频率漂移及Q值变化,而频率漂移及Q值变化,又与等离子体的电子密度及空间分布、电子瞬间跃迁碰撞频率和它的空间分布等参数密切相关.由一级微扰理论,共振腔频率漂移(?)ω与具有电导σ的等离子体的关系如下:     

高功率微波大气传输电参数优选研究

大气击穿将产生很大的不利影响,高功率微波大气传输过程中应避免发生大气击穿。分析了高功率微波大气击穿的微观机理,研究了高功率微波在自生等离子体中传输时的反射和透射特性,并进行了数值模拟,从而初步探讨了HPM发射参数的优选问题。计算结果表明:在一定环境下,当HPM的频率和场强一定时,HPM发射参数存在一个合适的脉冲宽度;当HPM的频率和脉冲宽度一定时,HPM发射参数存在一个合适的场强。     

临近空间高超声速目标RCS模拟技术研究

针对雷达探测临近空间高超声速目标模拟试验中的雷达散射截面（radar cross section，RCS）逼真模拟问题，提出了一种适用于临近空间高超声速飞行器等离子体鞘套下目标RCS衰减模拟方法.首先利用不同高度、不同速度对应的等离子体频率和电子碰撞频率的相关数据，拟合得出不同速度、不同高度对应的等离子体频率和电子碰撞频率关系表；其次，实时查表得到给定雷达频率情况下不同目标高度与速度对应的等离子体频率和电子碰撞频率，建立目标等离子体包覆模型和电磁波传输模型，计算雷达电磁波的衰减系数和反射系数；最后，通过雷达电磁波的衰减系数和反射系数模拟出目标RCS衰减.通过与有关实测数据比对，证明了方法的合理性.仿真分析可知，利用高频率雷达探测临近空间高超声速飞行器将更容易得到连续的航迹，产生雷达"黑障"的时间更短.     

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.     

Nanoimprint Lithography -A Next Generation High Volume Lithography Technique

IntroductionNanoimprint Lithography is a well-acknowl-edged low cost, high resolution, large area pattern-ing process. It includes the most promising methods,high-pressure hot embossing lithography (HEL) [2],UV-cured imprinting (UV-NIL) [3] and micro contactprinting (m-CP, MCP) [4]. Curing of the imprintedstructures is either done by subsequent UV-lightexposure in the case of UV-NIL or by cooling downbelow the glass transition temperature of the ther-moplastic material in case of HEL…     

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.     

Influence of PVK ： NPB hole transporting layer on the characteristics of organic light-emitting devices

A doping system consisting of NPB and PVK is employed as a composite hole transporting layer （CHTL）. By adjusting the component ratio of the doping system, a series of devices with different concentration proportion of PVK ： NPB are constracted. The result shows that doping concentration of NPB enhances the competence of hole transporting ability, and modifies the recombination region of charge as well as affects the surface morphology of doped film. Optimum device with a maximum brightness of 7852 cd/m^2 and a power efficiency of 1.75 lm/W has been obtained by choosing a concentration proportion of PVK ： NPB at 1：3.     

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.     

Analysis of error performance on Turbo coded FDPIM

Due to variable symbol length of digital pulse interval modulation（DPIM）, it is difficult to analyze the error performances of Turbo coded DPIM. To solve this problem, a fixed-length digital pulse interval modulation（FDPIM） method is provided. The FDPIM modulation structure is introduced. The packet error rates of uncoded FDPIM are analyzed and compared with that of DPIM. Bit error rates of Turbo coded FDPIM are simulated based on three kinds of analytical models under weak turbulence channel. The results show that packet error rate of uncoded FDPIM is inferior to that of uncoded DPIM. However, FDPIM is easy to be implemented and easy to be combined, with Turbo code for soft-decision because of its fixed length. Besides, the introduction of Turbo code in this modulation can decrease the average power about 10 dBm, which means that it can improve the error performance of the system effectively.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

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.     

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.