基于盲源分离的自适应抗干扰算法研究

在卫星导航系统遇到的干扰中,一般分为压制式干扰和转发式干扰。压制式干扰远大于卫星信号,采用功率倒置算法就可以形成所需的零陷;转发式干扰的信号强度可以与卫星信号相比拟,要在干扰位置处形成零陷存在一系列困难。在干扰信号与有用信号相比拟的情况下,提出将快速独立分量分析算法(fast independent component analysis,FastICA)结合自适应抗干扰算法对干扰进行抑制,自适应算法采用波达方向估计(DOA)算法及基于DOA的波束形成算法,该方法能在干扰与有用信号比拟的情况下,对干扰进行有效抑制,计算机仿真结果也证明了该方法的有效性。为导航系统中有效抑制弱干扰提供了一种新思路。     

一种强干扰条件下微弱信号DOA估计的新方法

给出了一种基于均匀线性阵列的既能抑制强烈干扰,又能同时进行微弱信号DOA估计的算法。在已知强干扰源个数和入射方向的前提下,先使用改进的波束形成方法,在子阵上进行波束形成以抗干扰,再对加权后的子阵进行微弱信号的DOA估计。该方法的优点是当干扰和希望信号处在同一个波束内时,不需要提高信号的信噪比就可以正确地估计出信号的入射方向。理论分析和计算机仿真都表明该算法是有效的。     

基于转换矩阵的GPS相干干扰抑制技术

本文首先采用空间平滑技术消除有用的GPS信号与相干干扰信号之间的相关性,然后构造干扰转换矩阵,从而抑制干扰信号,保留有用信号和噪声。最后根据最大输出信噪比原则,获得最佳波束形成器。仿真分析表明该方法可以有效提高输出信号的信号干扰加噪声比,且对信号的DOA估计不敏感。     

车载雷达架设控制系统集成设计

针对强相干干扰背景中弱信号的波达方向(DOA)估计问题,提出了一种基于迭代算法的弱信号DOA估计新算法。首先估计强相干干扰的波达方向,然后将阵列划分成两个子阵,进行子阵波束形成来抑制干扰并提高待估计的弱信号的信干噪比,最后利用子阵相位中心偏移进行DOA估计,为提高弱信号的DOA估计精度对以上过程进行迭代运算。该算法在强相干干扰环境下能有效进行弱信号DOA估计,而且估计精度较高。理论分析和计算机仿真结果验证了算法的正确性和有效性。     

子阵分级处理与稀疏恢复联合的抗主副瓣干扰方法

传统的抗干扰方法在低信噪比条件下性能恶化,对此本文提出了子阵分级处理与稀疏恢复联合的抗干扰方法。新方法首先按照一定规则将全阵列划分为多个子阵列;然后利用自适应波束形成（ADBF）技术抑制各子阵接收信号中的副瓣干扰信号,并将各子阵ADBF后的输出数据联合,构建新的阵列数据;最后通过新构建的阵列数据构建稀疏表示,改进了多测量向量降维提升法（ReMBo）,并与交叉方向乘子法（ADMM）联合进行稀疏恢复,分离得到目标回波信号,并得到了波达角（DOA）的估计。仿真实验表明,新方法能有效对抗主副瓣干扰,与其它方法相比,具有更好的目标检测和DOA估计性能,特别是在低信噪比的条件下。      

基于改进互耦系数估计算法的自适应波束形成

阵列信号在实际应用中,常常会面临噪声的干扰,低信噪比(signal noise ratio, SNR)时波束形成器性能会急剧下降. 针对该问题,提出一种基于改进互耦系数估计的抗互耦算法的自适应波束形成,即研究信号在不同输入SNR以及不同干扰波达方向(direction of arrival,DOA)估计误差下的互耦系数估计误差;并通过误差分析修正原算法不同SNR下参与估计信号的数目. 改进算法改进了导向矢量和期望信号,提高了低SNR下互耦系数估计的准确度,对比分析验证了其在低SNR情况下有更强的抗干扰能力,对互耦现象有着更好的稳健性.     

基于嵌套阵列的稀疏表示稳健波束形成方法

针对波束形成中目标方位失配以及噪声加干扰的协方差矩阵非精确重构造成的波束形成方法性能下降的问题,提出一种基于嵌套阵列的稀疏表示稳健波束形成方法。在该方法中,计算嵌套阵的采样协方差矩阵,通过差合作阵处理得到一孔径扩展的虚拟均匀线列阵;基于稀疏表示的方法来估计目标以及干扰的准确方位信息;进一步利用得到的方位信息构造导向矢量,通过最小二乘方法计算干扰信号的精确功率值;最后重构干扰加噪声协方差矩阵,通过波束形成实现干扰抑制。数值仿真表明,所提方法有效提升了干扰加噪声协方差矩阵重构精确度,在不同信噪比和快拍数条件下,输出信噪比都能逼近最优信干噪比,验证了该算法的有效性。     

高信噪比下的信号波达方向估计方法

自适应调零天线被应用于卫星通信和卫星导航领域,对于强干扰情况,方向图在干扰信号方向形成零陷,从而实现干扰抑制。利用自适应调零天线采用的功率倒置LMS自适应滤波算法,可以实现对信号的波达方向估计。新方法利用自适应调零天线实现过程中求得的权矢量,计算方向图,并把该方向图倒数定义为空间谱函数,该空间谱谱峰对应信号波达方向。观察空间谱图并对算法中的步长和信噪比进行分析,结果显示该方法可高分辨率地估计出DOA,并且步长越小,信噪比越大,估计误差越小。相对于已有的MUSIC谱估计方法,该算法无需进行信源个数估计,也无需进行信号协方差矩阵特征分解,实现更为简单。      

具有良好宽容性的逆波束形成干扰抑制算法研究

在阵列信号处理中,逆波束形成干扰抑制算法利用干扰的方位信息估计干扰信号从而进行干扰抑制,但在复杂海洋环境中阵列接收的干扰信号往往存在相位随机扰动,此方法估计的干扰信号与实际干扰信号有较大偏差,造成干扰抑制效果不理想。为适应干扰相位的随机扰动,具有良好宽容性的逆波束形成干扰抑制算法充分考虑随机扰动的存在,利用干扰重建矩阵估计干扰信号,此时估计干扰信号更接近实际干扰信号,保证干扰抑制有较好的结果。该文算法充分考虑了复杂海洋环境中干扰信号的相位扰动,可以获得较好的干扰抑制效果,提高了算法的宽容性。理论分析、计算机仿真结果均表明该文算法的有效性。     

立体阵卫星导航抗干扰波束形成算法性能对比研究

卫星导航系统采用扩频通信体制．传播到地面的卫星导航信号淹没在热噪声中．导航接收机极易受到有意或无意射频信号干扰。抗干扰是导航领域的研究热点。本文设计了三维立体阵结构,并对其应用多种波束形成算法进行波束形成抗干扰性能仿真对比。立体阵实现了全空域来波方向的二维辨识．MVDR波束形成算法实现了有效卫星信号的高增益接收、干扰信号的零陷抑制。     

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.