一种应用在多孔径宽测绘带SAR中的CS算法

多孔径接收宽测绘带SAR方法是一种较先进的高精度宽测绘带SAR成像方法。这种方法要求先对距离向信号压缩然后用反解矩阵求出各个测绘带的信号,然后再进行方位向聚焦。RD算法应用在这种成像方法比较方便,但是在星载SAR成像中大多用精度较高、运算量较小的CS算法。CS算法要求先进行方位向FFT而不是距离向压缩,所以不能直接应用在这种成像方法中。该文提出了一种基于CS算法的多孔径成像算法,可以很方便应用于多孔径接收宽测绘带SAR,并进行了计算量和误差分析,给出了仿真结果。仿真结果证实了本文所述方法的有效性。     

临近空间平台高分辨率宽测绘带重复访问合成孔径雷达成像模式及算法研究

本文提出一种临近空间高分辨率宽测绘带快速重复访问模式。发射天线采用线性相控阵列天线,结合合适的接收天线模式,共形成一个主瓣两个栅瓣,对同一成像区域快速重复访问。在方位向高分辨率及距离向宽测绘带的要求下,各子波束方位向回波在方位时域及频域均存在混叠。本文提出一种多通道多子波束重建算法,以对方位向各子波束回波进行分离。采用非线性调频尺度算法对分离后各子波束回波进行成像。并对各子图像的成像性能参数进行研究。本文给出了一个系统设计示例。实验仿真结果表明,本文提出的成像模式及所提出的信号处理流程正确有效。计算所得性能参数表明,各子图像质量可满足实际应用的要求。      

基于距离向多孔径接收的宽测绘带SAR成像方法的研究

该文提出了一种新的基于距离向多孔径接收宽测绘带合成孔径雷达(SAR)成像方法。首先对这种成像方法进行了严格的论证,并证明了运算中的加权矩阵为良态矩阵,然后分析了这种成像方法的计算量,讨论了这种宽测绘带SAR的信噪比,最后给出了仿真结果。     

合成孔径雷达成像中频带分割与子带处理技术研究

采用多收多发孔径的合成孔径雷达(SAR)可以获得较常规SAR更宽的测绘带和更高的空间分辨率。该文将频带分割技术应用到多收多发孔径SAR成像中,在实现方位向高分辨率的同时获得距离向高分辨率。针对同步收发的子带脉冲信号,提出了一种时域先合成再脉冲压缩的方法,并对频域子带先脉冲压缩再合成的方法进行了扩展,提出了非零中频子带脉冲压缩合成的方法,仿真结果证明了方法的有效性。文中研究了子带载频差对压缩结果及成像的影响,并通过计算机仿真分别对两种相位差的影响进行了说明。     

分布式小卫星多中心频率SAR实现宽域二维高分辨率成像

分布式小卫星SAR能够打破传统单星SAR测绘带宽和方位分辨率的矛盾。该文分析了一种沿航向排列分布式小卫星宽测绘带二维高分辨率成像技术,每颗卫星同时发射接收不同频率的线性调频信号,先分别在每个子带解方位多普勒模糊,并将方位多普勒中心频率调整至零频,然后在距离向进行子带拼接得到大带宽的线性调频信号从而得到高的距离向分辨率。此外,这种多发多收的工作方式还增加了系统平均发射功率,提高了信噪比。     

基于方位向波束扫描的宽测绘带SAR方法研究

宽测绘带合成孔径雷达(SAR)是目前SAR研究的一个热点问题，在需要全球动态观察或高重复周期观察局部地区的应用中都希望能进行宽测绘带成像。在宽测绘带SAR方法中的关键问题是如何在混叠的信号中提取出各个子测绘带的回波，在现有的宽测绘带SAR方法中多数是基于距离向多波束、距离向脉冲编码、距离向自适应聚焦等方法区分各个子测绘带的回波。文中提出了一种基于方位向波束扫描的宽测绘带方法，可以在方位向频谱上区分各个子测绘带的回波，从而在保持SAR分辨率的情况下扩展测绘带。     

艇载共形稀疏阵列天线雷达成像研究

基于平流层飞艇平台,研究了共形稀疏阵列天线雷达对静止目标成像及对运动目标探测的问题。针对三叶玫瑰线艇身模型,提出了共形稀疏阵列天线的布阵方式。雷达采用实孔径方式成像,各子阵同时发射多脉冲频分正交信号。利用各子阵多发多收的回波信号,采用后向投影(BP)算法完成各子带信号对静止目标的成像处理,再将子带信号成像结果相参累加以提高静止目标成像的距离向分辨率;将各子阵一发多收的多脉冲回波信号变换到距离-多普勒域,完成静止杂波抑制,对各子带信号采用压缩感知(CS)的方法在二维空间实现对运动目标图像的重建,再将子带信号重建结果非相参累加以提高运动目标探测的信噪比。仿真实验验证了本文方法的有效性。     

高分辨率宽测绘带Scan SAR压缩感知成像算法研究

高方位向分辨率和宽测绘带对合成孔径雷达（Synthesis Aperture Radar, SAR）系统设计提出了矛盾的要求。为获得高分辨率宽测绘带地面图像,提出了一种基于扫描模式SAR（Scan SAR）及压缩感知（Compressive Sensing, CS）理论的解决方法。Scan SAR可获得宽测绘带,然而各子测绘带方位向照射不完整,导致了低的方位向成像精度。所提出的方法首先对子测绘带数据进行方位向补零,并完成距离压缩和距离徙动校正;在方位向有效数据行中进行随机取样构成新的数据矩阵;根据取样指标集构建合理的重建矩阵,通过ROMP算法重建出完整的方位向点目标位置信息;通过子测绘带图像拼接,即可获得高分辨率宽测绘带地面图像。仿真结果表明了所提出方法的有效性。      

超高分辨大测绘带星载MIMO-SAR成像

星载多发多收合成孔径雷达(MIMO-SAR)可以解决方位向高分辨和大测绘带之间的矛盾.为了在扩大测绘带宽度的基础上进一步实现距离向超高分辨,首先选用正交频分线性调频信号( OFD-LFM)作为发射信号形式,对MIMO-SAR的发射体制进行了初步设计;然后针对大带宽、宽测绘带对成像算法的限制,选用精确度高的距离徙动算法(RMA)对回波数据进行处理,给出了结合空频域带宽合成的RMA成像流程,相比时域带宽合成方法,在确保成像精确性的同时,文中的成像流程计算步骤更少,运算量更低,大大提高了计算效率.     

高分辨率宽测绘带星载SAR距离向DBF处理

该文在研究星载SAR使用距离向数字波束形成(DBF)实现宽测绘带的基础上,通过理论推导和仿真分析了仅做时域加权DBF处理对成像结果幅度和分辨率的影响,并进一步针对DBF-SAR扫描接收方式研究了4种适用于不同发射信号脉宽的距离向DBF处理方法。仿真验证了4种处理方法在各自的前提下能有效实现距离向宽测绘带接收。     

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.     

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.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

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.