结合图像处理与时频分析的直扩/跳频信号参数估计

为实现扩频带宽大于跳频间隔、干扰信号强度较大及存在信道噪声时直扩/跳频(DS/FH)信号参数精确估计,提出了一种结合图像处理算法与时频分析技术的DS/FH信号参数估计方法。该方法首先利用时频分析算法提取DS/FH信号的时频分布图,然后结合干扰分量在时频图中的图像特征,利用图像处理的开运算与闭运算剔除了图像中的孤立干扰点及"空洞"干扰点。特别地,为抑制复杂的毛刺干扰信号提出了一种迭代相关匹配算法。最后通过分析图像像素位置与时频参数的对应关系完成DS/FH信号的参数估计。仿真实验表明,该方法可以有效消除干扰信号的影响,准确快速提取混合扩频信号的时频参数。     

基于时频域分析的雷达有源干扰识别方法及实现

通过分析雷达压制干扰信号、欺骗干扰信号的时频域特征,设计了一种基于时频域分析的干扰信号识别方法,并描述了其实现方法。为保证干扰信号识别的实时性和准确率,利用数字信道化接收机原理进行信号预处理,获取信号的时频功率谱、高分辨率功率谱以及脉冲描述字(PDW)数据,后续由数字信号处理器(DSP)芯片多核并行处理完成干扰识别分类。     

应用小波变换于电磁场目标后向散射信号的时频图分析

本文将Ｍｏｒｌｅｔ小波用于电磁场后向散射信号的时频分析，为了更好地提高时频分析的时间和频率分辨率，我们对Ｍｏｒｌｅｔ小波进行了改进，并合理地选择尺度的变化规律，数据结果证明无论地同时提高时频分辨率还是抗噪声能力上，改进的Ｍｏｒｌｅｔ小波时频分析都优于短时傅里叶变换和Ｗｉｇｎｅｒ－Ｖｉｌｌｅ分布。     

四种时频分析方法的频率分辨率研究

时频分析是分析时变谱的有力工具,其频率分辨率是值得研究的关键问题之一。通过对基于短时傅里叶变换、小波变换、Choi-Williams分布和Hilbert-Huang变换的四种时频分析方法的频率分辨率的实验比较,说明Hilbert-Huang变换法具有最高的频率分辨率,其次是Choi-Williams分布,小波紧随其后,最差是短时傅里叶变换。     

一种用于地震信号分析的二阶挤压小波变换算法

地震信号分析在地质岩性、储层、流体、沉积相带的检测,以及地层界面识别与储层分析、地震资料处理和解释等方面具有重要研究意义。针对现有时频分析算法在处理地震信号时,存在时频分辨率低、能量聚集性差等问题,该文以Ricker子波为数学模型,提出了一种新的2阶挤压小波变换算法(SWT2)。考虑到传统时频同步压缩变换中的瞬时频率估计对地震信号失效,利用改进的母小波对地震信号进行匹配,进而通过谱峰对齐对参考频率进行修正,从而提升时频能量聚集性和时频分辨率。仿真实验结果表明,提出的2阶挤压小波变换算法可以极大地提升地震信号的时频聚集性,精确地反映信号的时延和主频,对地层结构的刻画更加精确。     

自适应时频同步压缩算法研究

提高时频分辨率对多分量非平稳信号的分析与重建具有至关重要的作用。传统的时频分析方法由于窗口固定,分析频率变化较快的信号时存在时频聚集性不高的问题,无法自适应分辨多分量信号。该文针对频率快速变化信号,利用信号的局部信息特征,提出一种自适应的时频同步压缩变换算法。该方法有效提升了已有同步压缩变换时频分辨率,特别适用于频率接近且快速变换的多分量信号。同时,利用可分性条件,该文提出利用局部瑞利熵值对自适应窗口参数进行估计。最后,通过对合成信号和实测信号分析,证明了所提方法的可行性,对分析和重建复杂非平稳信号具有重要意义。     

基于二次型时频分析方法处理非平稳信号

使用时频分析方法处理非平稳信号,提取非平稳信号的时频分布。分别采用线性时频分析和二次型时频分析处理模拟仿真信号,仿真结果显示用二次型时频分析处理所得的时频分布的时频分辨率较高。仿真结果证明,二次型时频分析方法是处理非平稳信号的有效方法。     

基于WD和时频滑窗掩膜的SAR干扰抑制算法

窄带干扰(NarrowBand Interference,NBI)和宽带干扰(WideBand Interference,WBI)的存在将会大幅度地降低合成孔径雷达(Synthetic Aperture Radar,SAR)图像的质量.本文在对NBI和WBI的时频分析基础上,提出了一种基于Wigner分布(Wigner Distribution,WD)和时频面滑窗掩膜技术的干扰抑制算法.该算法首先利用瞬时时刻重构序列与原序列之间的联系,提出了一种基于WD的高效信号重构算法.然后采用平滑伪WD分布(Smoothed Pseudo Wigner Distribution,SPWD)作为时频掩膜抑制WD的交叉项,并结合WD信号重构算法和时频平面滑窗掩膜技术提取并重构干扰信号,最后将重构的干扰信号在原始回波中对消实现干扰抑制.该算法能有效抑制SAR图像中的时变NBI和WBI,同时能够尽可能保留有用信号.仿真数据和实测数据结果分析验证了本文方法的有效性.     

常规时频分析方法对比分析研究

时频分析技术兼具时间域和频率域特性,它根据地震波在地下传播时衰减与频率相关以及油气对于频率的敏感性,利用时频分析技术将信号从时间域变换到频率域进行信号分析。文章阐述了时频分析技术中的短时傅里叶变换(STFT)、S变换(ST)、匹配追踪Wigner-Ville分布(MP-WVD)三种变换方法;对比三种方法,得出匹配追踪Wigner-Ville分布的时频变换方法兼具了时频原子的独立性和高时频分辨率的特性,在实际地震资料的时频分析中表现出了对信号的较高品质的时频表示。     

利用时频分析的间歇采样干扰对抗方法

为了提高线性调频脉压雷达在复杂电磁环境下的抗干扰能力,提出了基于时频分析的间歇采样干扰识别与抑制算法。针对间歇采样干扰信号在时域上的不连续性,将雷达接收信号通过扩展处理中的混频处理之后再进行时频分析,通过对时频分析结果的处理进而提取一种特征参量,对雷达接收信号中是否存在干扰进行鉴别;同时将扩展处理与时频分析相结合,根据时频分析求解合适的带通滤波器,用以对雷达接收信号扩展处理的结果进行滤波,从而消除干扰。理论推导和计算机仿真结果表明,这种方法能够在合理的信噪比下鉴别出雷达是否受到间歇采样干扰,并且能够进行有效的抑制。      

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.