基于压缩感知的稀疏采样数据大转角ISAR 成像研究

针对方位向稀疏采样条件下,大带宽大转角逆合成孔径雷达(ISAR)高分辨成像时,一维距离像中目标散射点的距离徙动问题,提出了基于贝叶斯压缩感知的稀疏ISAR 成像方法。对于方位向稀疏采样数据,该方法在包络对齐和相位补偿后,通过傅里叶变换将数据变换到距离频率域,对每一距离单元数据,根据方位向稀疏采样的位置构造相应的Keystone基矩阵,利用贝叶斯压缩感知算法重建目标在各距离频域单元的多普勒域系数,最后,通过距离向逆傅里叶变换和方位向自聚焦完成ISAR 成像。计算机仿真验证了该方法的有效性。     

一种ISAR目标转动补偿及图像尺寸标定方法

通过对逆合成孔径雷达(ISAR)匀速平面旋转体散射中心的距离和多普勒走动分析,提出一种ISAR目标转动速度及旋转中心估计算法,并实现目标聚焦成像.该方法通过Keystone变换补偿一阶距离走动,采用匹配处理补偿一阶多普勒走动,从而实现对非合作目标的转动补偿和聚焦成像.进而,通过图像质量评价获得目标转速和等效旋转中心联合估计.结合对目标的转动估计,提出了较完整的高分辨ISAR聚焦成像及图像尺度标定的处理流程,并分析了其应用条件.最后,通过实测飞机目标数据验证了该方法的有效性.     

空间目标卡尔曼滤波稀疏成像方法

鉴于卡尔曼滤波器(KF)具有优良的信号估计性能,将KF与贪婪算法相结合,该文给出稀疏约束下的基于KF的空间目标逆合成孔径雷达(ISAR)成像方法。考虑到有些空间目标尺寸较大或包含大尺寸部件,或成像积累时间较长,会引入越分辨单元走动(MTRC)和方位向2次相位调制,首先对回波进行MTRC校正,然后构建包含2次相位的观测矩阵,通过使图像锐度最大化,估计目标转动角速度,获得聚焦目标图像,并将估计转速用于方位向图像定标。卫星仿真ISAR数据处理验证了上述成像处理方法的有效性。成像效果优于传统距离多普勒(RD)和正交匹配追踪(OMP)方法。     

一种微波光子雷达ISAR成像新方法

微波光子雷达发射信号带宽大、波长短,能够实现分辨率更高的逆合成孔径雷达(ISAR)成像。但带宽大、波长小的回波信号也导致传统成像算法对目标转动分量的近似不成立,使得传统算法无法应用。在微波光子雷达成像中,目标转动分量在回波包络中形成空变的距离弯曲项,在方位相位中形成空变的2次相位误差,导致ISAR图像散焦。该文针对微波光子雷达系统提出一种新的ISAR成像算法,该算法同时考虑了目标转动分量对回波包络和相位的影响,以包络相关值为目标函数值迭代估计目标转速,根据转速估计值,在距离向进行重采样对齐包络,在方位向构造空变的方位补偿函数校正转动相位。仿真和实测数据的处理结果证明了该算法的有效性。     

基于相干化处理的步进频率ISAR成像算法研究

在步进频率高分辨ISAR成像中,传统的参数估计方法往往不能准确地估计出运动目标的速度和加速度值,其补偿后存在的相位误差对宽带合成ISAR图像有较大的影响。因此,该文提出了一种基于相邻相关法和相位相干化的步进频率高分辨ISAR成像技术,即通过相邻相关法估计运动目标的径向运动参数,在对回波数据包络进行补偿后,利用相位相干化对各子脉冲的相位误差进行校正,再利用频带拼接技术获取目标的合成高分辨1维距离像。之后,利用RD算法实现目标的高分辨ISAR成像。该方法具有精确相位误差补偿精度和高运算效率的优点。仿真和实测数据验证了该方法的有效性。     

提高ISAR分辨率的两种外推方法性能之比较

从ISAR成像原理出发,分析了散射点越距离单元走动（MTRC）对ISAR分辨率的影响,通过高分辨DFT数据矩阵求逆和AR模型进行方位谱数据外推;对不同的信噪比条件下,两种方法外推前后ISAR像的距离和方位分辨率及相关性作了比较分析：分析表明,方位谱外推的方法可在提高方位向分辨率的同时,有效地克服MTRC对距离向分辨率的降质,从而提高ISAR的成像质量。     

基于块稀疏的空间碎片群目标成像方法

针对星载雷达空间碎片群目标回波无法分离问题,该文利用回波在距离向表现出的块聚集特性,提出一种基于块稀疏的高分辨ISAR成像方法。基于块稀疏压缩感知理论,通过利用空间碎片群目标特性,抽取出各个碎片的高分辨1维距离像数据,并结合平动补偿和距离多普勒(RD)算法得到各碎片的ISAR像。在小样本条件下,该方法能够有效实现空间碎片的数据分离和高分辨ISAR成像。仿真实验表明,该方法的重构精度以及运算速度均优于非结构类的稀疏ISAR成像方法。     

利用二维结构稀疏信息的调频步进ISAR高分辨成像新方法

针对已有利用压缩感知理论进行逆合成孔径（Inverse Synthetic Aperture Radar,ISAR）成像方法在低信噪比、欠采样率条件下性能下降严重等问题,依托调频步进波形独有特征并充分利用目标分布的二维结构稀疏信息,提出一种"先方位聚焦后距离分辨"的调频步进ISAR高分辨成像新方法.首先,对回波进行子脉冲脉压,在分析调频步进ISAR回波方位向特有的结构稀疏特征基础上,构建方位向的分布式压缩感知稀疏重构模型;其次,采用分布式压缩感知算法对该模型重构,从而获得低信噪比条件下的方位高分辨成像;最后,利用距离维的回波特征构建任意稀疏重构模型,实现距离向快速成像.由于该方法先进行方位聚焦,再进行距离分辨,并充分利用了目标的结构稀疏性,因此不仅具有抗噪性能强、重构精度高以及采样率低等特点,且避免了越距离单元走动对方位聚焦的影响.仿真与实测数据实验验证了本文方法的有效性.     

一种高精度的ISAR转动补偿和方位定标方法

传统逆合成孔径雷达(ISAR)成像算法忽略了目标回波的高阶转动相位的影响,导致方位向聚焦效果较差,且无法直接从目标图像中获取目标尺寸信息。该文提出一种转动补偿和方位定标方法。该方法采用回波的全部方位信息,通过构造局部平均多普勒趋势(LADT)信号获取目标回波的多普勒变化趋势。进一步利用随机采样一致(RANSAC)算法估计多普勒调频率及目标有效转动速度,实现高精度转动补偿与方位定标。仿真与实测数据实验验证了该方法的有效性。     

调频步进雷达ISAR成像方法

针对调频步进雷达的ISAR(Inverse Synthetic Aperture Radar)成像问题,提出了一维距离像和ISAR成像的分步补偿方法.通过优化雷达系统参数,在保证抽取损失和伪峰幅度在容许范围内的同时最大化了一维距离像的速度补偿误差容限.一维距离像运动补偿参数通过拟合子脉冲包络对齐的平移量获得,当拟合脉冲数足够多时,估计精度在一维距离像的速度补偿误差容限以下;对目标一维距离像进行包络对齐和相位聚焦完成ISAR成像的运动补偿.最后,通过仿真分析验证了算法的可行性.     

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.     

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.