采样定时偏差对无源雷达性能影响研究

外辐射源雷达利用第三方信号作为照射源来探测目标,参考通道中的信号重构和监测通道中的杂波抑制是外辐射源雷达信号处理流程中的关键部分。主要讨论了OFDM波形照射源信号,并从理论上分析了采样定时偏差在参考信号重构、时域杂波抑制和匹配接收性能的影响。理论分析和仿真表明,采样定时偏差的存在会减少重构后的参考信号和监测信号的相关性,降低时域杂波抑制性能以及匹配接收的目标信噪比。基于WiFi信号帧结构的特点,提出了一种对采样定时偏差估计和补偿的方法,并在实测数据中验证了该方法的有效性。     

基于数字电视广播信号的无源雷达实验研究

针对无源雷达杂波抑制问题,提出了采用空域滤波和双极化通道对消的方法。设计了一套多通道宽带接收与处理系统,选择DTTB数字电视广播信号开展了民航飞机目标探测实验,采用极化和空域滤波方法解决了由于实验系统布站带来的强直达波抑制问题;结合DTTB数字电视广播信号特点给出了分块处理方法中块长度合理选择区间;通过实验数据分析了不同极化通道杂波对消性能,结果表明该无源雷达实验方法能够提升无源雷达探测能力。     

基于调频广播的外辐射源雷达抗干扰技术

基于调频广播照射源的外辐射源雷达具有抗隐身、反侦查和较强的生存能力等优点,渐渐得到了大家的重视。针对雷达系统中较强的直达波、多径信号以及同频等干扰信号对目标探测性能的严重影响,提出了空-时自适应处理技术来抑制干扰信号。重点分析了最大信干噪比(MSINR)准则的空域自适应处理和改进型递推最小二乘(RLS)算法的时域自适应处理,利用在实际工程系统中采集的数据对空时自适应处理算法进行仿真分析和验证,检测到干扰抑制前系统无法检测到的目标,目标的信杂比提高了10 d B以上。     

数字电视广播外辐射源雷达子带处理方法研究

数字电视广播外辐射源雷达的信号带宽大、基带采样率高,使得该体制雷达面临数据实时传输和处理的困难。针对基于中国移动多媒体广播(CMMB)信号的外辐射源雷达,利用CMMB信号的部分带宽来降低基带采样率,提出一种子带处理方法。其中,重点研究了重采样率设置、参考信号子带提纯和子带匹配问题,并结合多径杂波抑制和匹配滤波处理分析子带宽度和纯度对目标探测性能的影响。仿真和实测数据处理结果验证了所提方法的有效性,为该体制雷达的实时化奠定了基础。     

GNSS外辐射源空中目标探测研究现状及发展

外辐射源雷达是依靠其他辐射信号进行探测的雷达，具有成本低廉、战场生存能力强、反隐身性能优秀和抗干扰能力突出等特点，是当前多个领域的研究热点。导航卫星信号具有带宽宽、旁瓣低和全天候全地域覆盖的特点，且作为外辐射源信号可无损重构。针对外辐射源雷达的发展现状，从外辐射源探测、主要外辐射源信号对比分析、外辐射源雷达的关键技术和研究难点等方面进行概述，得出导航信号作为外辐射源信号的优势所在及其以弱信号检测和杂波抑制为主的研究难点，并就已有技术提出初步的解决方案。从多雷达布站方案、双站极化处理和双基雷达成像等方面对GNSS外辐射源目标探测技术的发展趋势提出展望。     

基于压缩感知的外辐射源雷达目标检测

外辐射源雷达是利用电视、广播等非合作照射源对运动目标进行探测、定位和跟踪的雷达系统。由于目标回波信号功率微弱,淹没在直达波、多径杂波以及接收机热噪声中,一般需要通过杂波对消和相干积累来检测目标。考虑到回波信号互模糊函数在距离-多普勒域的稀疏性,建立了基于压缩感知(Compressive Sensing,CS)的外辐射源雷达目标检测模型。该模型对辐射源信号形式没有要求,不需要杂波对消,并且在强目标存在的情况下不影响对弱目标的检测。仿真结果表明:基于该模型的方法在性能上与常规方法相当,并且在强目标存在时也能有效检测到弱目标。     

外源雷达空时联合恒虚警检测分析与实验

外辐射源雷达杂波呈现复杂形态,其中在距离多普勒谱中固定分布的剩余杂波（简称固定杂波）局部强度较高,采用空域恒虚警检测方法会造成连续的虚警,严重影响目标检测性能。本文通过实测数据分析发现,固定杂波强度在时域变化平稳,可采用时域杂波图检测方法减少该类杂波造成的虚警。然而,非理想信号波形导致外辐射源雷达目标回波具有较高的副峰和旁瓣,仅采用杂波图检测方法会导致重复检测和虚假航迹。通过分析空域和时域恒虚警检测方法面临的问题,本文提出了针对外辐射源雷达的空时联合恒虚警检测方法。该方法在不影响检测概率的前提下,减少了单一恒虚警检测方法造成的虚警。实测数据处理结果验证了所提方法的有效性。     

宽带外辐射源雷达系统设计与原理实验

外辐射源雷达使用第三方发射的电磁信号进行目标探测和定位,利用一个或多个发射站不同频率的广播照射源进行目标探测可以扩大外辐射源雷达覆盖范围,提高目标检测能力和探测精度。针对外辐射源雷达多频探测的需求,设计了一种高集成度、小型化宽带外辐射源雷达系统。最后基于双频DTMB信号目标探测进行了外场实验,介绍了实验场景以及信号处理流程,给出了初步探测实验结果。外场实验验证了该系统良好的目标探测性能。     

基于5G的外辐射源雷达模糊函数研究

随着低空空域开放和无人机等航空技术的发展,对城市或郊区等电磁频谱紧张的区域开展低空目标探测愈发重要,采用5G信号作为机会照射源的外辐射源雷达在该领域展现出了广阔的应用前景。相比4G网络,5G波形方案的实现细节发生了本质的改变,因此基于不同外辐射源信号的模糊函数也存在较大差异,而现有文献对基于5G信号的外辐射源雷达模糊函数的相关研究仍然较为缺乏。本文从信号的基本结构入手,采用对比分析的方法,从理论上对5G信号和4G信号在帧结构及物理资源结构等方面存在的差异进行了详细对比;搭建了系统仿真模型,并对基于5G信号的外辐射源雷达的模糊函数进行了仿真实验;最后,针对模糊函数中的各类副峰,分析了该模糊副峰产生的原因以及可能对信号探测性能造成的影响,并对部分副峰的抑制方式进行简单阐述。该文为基于5G信号的外辐射源雷达副峰的抑制提供了新的思路和方向。     

基于GSM基站信号的动目标探测方法

基于全球移动通信系统(GSM)蜂窝网信号的外辐射源系统,提出了一种利用GSM蜂窝网基站发射的信号实现对运动目标检测的外辐射源系统的方案。首先对GSM基站信号参数、信道特点、模糊函数进行了分析,然后给出了一个试验系统的组成及其处理方法,主要包括自适应直达波/杂波对消、相干检测及参数提取方法等,仿真分析了2种场景下的动目标检测及参数提取结果,验证了利用GSM信号进行目标探测体制的可行性。     

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.     

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.     

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.     

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.     

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.     

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.     

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