基于小波降噪和盲源分离算法的信号分离方法研究

针对含噪情况下的盲源分离问题,将小波降噪方法引入盲源分离模型之中,对两种小波降噪与盲源分离算法结合的信号分离方法,即预降噪+盲源分离,以及预降噪+盲源分离+后降噪,从理论上进行了原理与特点分析,并通过数值仿真比较了不同信噪比情况下两种方法对于混合信号的分离效果。仿真表明,采用小波降噪与盲源分离结合的信号分离方法,相比于单纯采用盲源分离算法,能够大大提高信号的分离效果;预降噪+盲源分离+后降噪的信号分离方法比采用预降噪+盲源分离的信号分离方法效果普遍提高。     

一种小波阈值降噪改进算法

基于Stein的无偏估计原理的自适应小波降噪阈值选择(rigrsure)算法,利用小波变换分解低信噪比下的Block信号,使用rigrsure算法获得重构后的低频信号和各层细节信号小波降噪阈值,提出了一种改进降噪算法,对Block信号降噪,通过仿真取得良好的降躁降噪效果。     

基于相关运算的低信噪比盲源分离抗干扰算法

针对传统盲源分离算法在低信噪比时分离性能较差的情况,提出一种基于相关运算的盲源分离抗干扰算法.该算法通过对训练序列进行分段相关运算并进行信号能量累积,实现信噪比提高.该算法实现简单,可改善低信噪比条件下的扰信分离效果.仿真结果表明,改善程度与训练序列的相关性及其分段长度成正比,并且在信干比为-15 dB时,至少可以在信...     

基于变分模态分解的自适应滤波降噪方法

为了提高分析信号的信噪比,本文提出了一种基于变分模态分解的变步长归一化最小均方自适应滤波降噪方法.该方法对原信号进行变分模态分解并区分信号分量和噪声分量,再对噪声分量进行间隙阈值降噪处理并将其作为参考信号输入自适应滤波器,通过自适应算法迭代处理得到降噪后的信号分量,并通过重构算法得到最终降噪后的信号.本文还在变分模态分解的基础上使用小波阈值降噪和间隙阈值降噪方法按不同方案进行降噪处理并得到最佳算法,将其与所提算法进行对比.实验结果表明,本文所提自适应滤波降噪方法的降噪效果比阈值降噪最佳方法效果更好.     

基于改进的盲源分离算法抗主瓣SMSP干扰

针对基于最大信噪比的盲源分离算法在信干噪比较差环境中无法有效分离信号和干扰的情况，提出了一种改进的基于最大信噪比的盲源分离算法，使用经过小波阈值去噪后的观测信号作为新的观测信号，重新构建最大信噪比目标函数，实现在高信噪比条件下的干扰分离。通过计算机仿真，在频率分集阵列-多输入多输出雷达系统中实现了在高信噪比条件下弥散干扰的分离。结果表明：相比于原始算法，改进后的算法能够很好地实现目标与干扰信号的分离。     

基于子空间和小波降噪的盲信号干扰抑制算法

卫星通信信号十分微弱,信噪比的改善以及抗干扰能力的增强对于信号的正确接收具有至关重要的作用。提出了一种星上干扰抑制方案和一种基于子空间和小波降噪的盲分离干扰抑制算法,对提出的算法在单音、多音、窄带噪声以及宽带噪声干扰下进行了误码性能仿真。结果表明,该算法克服了传统基于前置小波降噪的盲分离算法在干信比大于30dB时性能恶化的问题,提高了抗高斯白噪声性能。     

基于盲源分离的数字通信抗干扰技术

分析了现有数字通信抗干扰技术存在的局限性。在研究了盲源分离（Blind Source Separation,BSS）的理论基础上,介绍了一种基于盲源分离的数字通信抗干扰技术。建立了基于最大信噪比算法的盲源分离数字通信抗干扰传输模型,应用MATLAB仿真实现了2FSK通信信号与多种干扰信号的分离提取。仿真结果表明：应用基于盲源分离的抗干扰技术能够获得显著的抗干扰性能。     

基于小波包-FHN模型的UWB信号检测

在超宽带冲激无线电信号检测中,针对FHN神经元模型随机共振中检测信噪比受限的问题,研究分析了小波包理论及传统单阈值小波包的缺点,结合新的分段阈值小波包去噪算法,提出一种小波包与FHN神经元模型随机共振联合检测的新方法,并对所提算法的性能进行仿真验证。仿真实验表明,新方法克服了FHN模型的信噪比门限,降低了FHN模型的检测信噪比,改善了FHN模型的检测性能,可有效恢复强噪声背景下的超宽带冲激无线电信号波形。      

低信噪比下多高斯脉冲组成的激光雷达回波信号滤波算法

针对激光目标回波信号在高信噪比与低信噪比时脉冲波形不同的特点,研究设计了针对低信噪比下多高斯脉冲组成的回波信号进行降噪的小波滤波算法。首先介绍了光电探测中信噪比的定义,给出了不同信噪比下脉冲回波的实际波形。接着,研究了高信噪比时激光回波的时域积累及差分平滑滤波算法,仿真并分析了算法性能。随后,对低信噪比下多高斯脉冲组成的目标脉冲波形采用小波低频系数重构滤波,通过仿真实验选择了合适的小波基以及分解层级。     

变分模态分解联合改进小波阈值函数的PPG降噪算法

针对PPG信号采集过程中存在大量混合噪声的问题,提出一种变分模态分解（VMD）改进小波阈值降噪的降噪算法。首先通过傅里叶变换得到脉搏波信号频域信息,确定分解个数和主频率;然后利用变分模态分解算法将含噪声的PPG信号分解为一系列固有模态分量,分解过后确定各分量的中心频率,并筛选有效固有模态分量;最后利用改进后的小波阈值函数对残余噪声进行降噪处理,避免了软阈值的恒定偏差,又保证了阈值函数的连续性,降噪后的信号与原始信号相关系数均值为0.934 7,比变分模态分解方法重构信号提升了7.1%。与其他降噪算法相比,信噪比分别提高了5.77 dB、5.38 dB、4.5 dB,均方根误差分别降低了26.1%、16.8%、7.4%。实验结果表明,通过理论计算、数值模拟和应用研究验证了所提方法的有效性和优越性,在滤波效果和信号保真度之间取得了很好的平衡。     

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.