基于压缩感知的被动雷达导引头信源数估计方法

随着雷达反摧毁技术的发展,被动雷达导引头面临着在雷达和诱饵形成的不完全重合信号中进行超分辨测向的挑战,需要单快拍测向技术。现有测向技术大多假设信源数已知,而传统的信源数估计方法在单快拍时性能大幅下降甚至失效。为解决这一问题,提出了一种基于压缩感知的单快拍信源数估计方法。该方法首先将被动雷达导引头阵列测向模型稀疏表示,其次通过子空间算法和压缩感知算法相结合进行降阶和解相干处理,然后提出一种改进的正交匹配追踪算法,研究残差的变化规律,最后构造目标函数估计信源数。仿真实验表明,该方法在单快拍、阵元数少、信号相干的极端情况下估计成功率较高。     

压缩感知宽带接收机的电路字典基获取技术

研究压缩感知用于信号采样的工程化问题,给出了MWC（Modulated Wideband Converter）结构压缩感知宽带接收机的具体设计方案,提出了字典基自环测量获取方法和字典基的时延估计补偿算法,有效解决了工程化中因观测电路存在传输时延、通带波纹等与理论观测矩阵不一致,导致压缩感知处理数字调制信号时存在重构畸变的问题.实验测量了接收机的频率覆盖范围,验证了压缩感知的有效性,并以QPSK（Quadrature Phase Shift keying）信号解调误码率为标准量化评估了压缩采样造成的信号质量损失.     

基于秩极小化的压缩感知图像恢复算法

本文将压缩感知图像恢复问题作为低秩矩阵恢复问题来进行研究.为了构建这样的低秩矩阵,我们采样非局部相似度模型,将相似图像块作为列向量构建一个二维相似块矩阵.由于列向量间的强相关性,因此该矩阵具有低秩属性.然后以压缩感知测量作为约束条件对这样的二维相似块矩阵进行低秩矩阵恢复求解.在算法求解的过程中,使用增广拉格朗日方法将受限优化问题转换为非受限优化问题,同时为了减少计算复杂度,使用基于泰勒展开的线性化技术来加速算法求解.实验表明该算法的收敛率、图像恢复性能均优于目前主流压缩感知图像恢复算法.     

基于信号子空间的ESPRIT-Like算法在相干DOA估计中的应用

相干环境中DOA估计的一个主要任务是在预处理中设法消除空间协方差矩阵的秩损失,首先分析了相干信号对基于子空间的超分辨算法的影响,随后从矩阵重构的思路出发,提出了一种基于信号子空间的ESPRIT-Like算法,最后通过仿真结果证明该方法的有效性与优越性.     

一种基于能量的压缩感知稀疏度估计算法

压缩感知理论中,信号稀疏度直接关系到采样速率的设定以及观测矩阵的构造,而该先验信息往往受限.针对这一问题,本文从大维随机矩阵谱分析理论出发,分析了采样协方差矩阵的极限特征值概率分布特征,并结合其与观测信号能量的关系推导得到观测信号能量与压缩率、稀疏度和信噪比之间的对应关系,提出一种基于观测信号能量的稀疏度估计算法.相对于已有算法,该算法计算复杂度较低,且估计精度较好,并可通过增加采样开销进一步提升稀疏度估计精度,仿真实验验证了本文算法的有效性.     

基于TOEPLITZ重构的压缩感知嵌套阵列DOA估计

针对传统稀疏阵列波达方向（DOA）估计算法在小快拍数、低信噪比和多信源数等条件下的估计精度不高的问题,提出了一种基于TOEPLITZ重构的压缩感知嵌套阵列DOA估计方法。首先利用TOEPLITZ重构方法将虚拟阵列的输出信号向量构建成满秩协方差矩阵,然后利用信号在空间域的稀疏性,将阵列协方差矩阵进行稀疏表示,通过噪声子空间和信号子空间的正交关系构建权值向量,对稀疏向量进行加权约束,最后通过求解最优化方程获取入射信源的DOA估计。仿真结果表明,本文方法比传统稀疏阵列DOA估计算法在低信噪比、小快拍数和多信源数下具有更好的DOA估计性能。     

基于自适应投影矩阵的压缩感知超宽带信道估计

超宽带信号由于功率谱密度较低和传输多径复杂,准确的信道估计十分重要。考虑其过高带宽带来的采样难度较高的问题,压缩感知理论提供了一种可行的低速采样方法。而目前常用的随机投影矩阵与超宽带信道稀疏变换矩阵相关度较高,算法必须在降维比较高时才能达到重构要求,采样速率依然较高。针对上述问题,提出使用贝叶斯压缩感知理论中的自适应投影矩阵设计方法进行超宽带信道估计。贝叶斯压缩感知理论给信道向量中的每个值设置受超参数控制的后验概率密度,计算信道向量的统计特性,并根据协方差矩阵计算新的投影向量,该投影向量可以使重构解的微分熵下降最快。通过这种自适应的投影矩阵设计方法,可以利用较少的采样值进一步地提高重构解的可信度,达到进一步降低采样速率的目的。实验结果表明该方法相对于现有的压缩感知重构算法可以在较低的降维比条件下达到较好的重构效果,显著降低了采样速率。     

基于贝叶斯压缩感知的子空间拟合DOA估计方法

经典加权子空间拟合算法需进行多维非线性优化,初始参数的难以设置和较大的计算量限制了其应用。结合压缩感知理论,本文提出了一种基于改进贝叶斯压缩感知的子空间拟合DOA估计新方法。该方法首先通过低复杂度的子空间分解算法PASTd估计信号加权子空间,进而基于入射信号的空域稀疏性,将信号子空间拟合建模为多测量值稀疏重构问题,并应用贝叶斯压缩感知算法进行求解。算法在贝叶斯压缩感知的迭代求解中引入了基于相对阈值判决的基消除机制,加快收敛速度的同时避免了矩阵奇异问题。仿真结果表明本文算法在低信噪比、小快拍情况下空间分辨率优于MUSIC和l1-SVD算法,可直接用于相干源的估计,并对信源数目的估计误差具有较强鲁棒性。      

雷达高分辨率紧凑感知矩阵追踪算法

针对压缩感知雷达的感知矩阵相干系数随分辨率增加而增大以致不能以大概率对稀疏向量进行完美重构的问题,直接基于原始感知矩阵,提出紧凑感知矩阵追踪(CSMP)算法。该文将CSMP算法应用于十字阵雷达的2维波达方向(DOA)估计并进行了计算机仿真。仿真结果表明与多信号分类(MUSIC)算法,子空间追踪(SP)算法,基追踪(BP)算法和稀疏贝叶斯学习(SBL)算法相比,基于CSMP算法的DOA估计分辨率得到了较大提高。     

基于压缩感知的空间谱估计

以多重信号分类（Multrple Signal Classification,MUSIC）算法为代表的现代空间谱估计方法,估计的信源数受限于阵列形式,并且需要的采样数据量巨大.文章从压缩感知的基础理论出发,利用目标信号空间分布的稀疏性,建立了基于压缩感知的阵列信号空间谱估计模型.利用压缩感知方法,可以使用较少的阵元数对空间信号进行采样测量,并准确重构信号.相比传统的MUSIC空间谱估计算法,该方法所需阵元数少,采样数据量小,并且能同时进行信号强度和角度的估计.所提方法对推动压缩感知理论在阵列信号空间谱估计中的应用具有一定意义.     

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.