圆周SAR子孔径频域成像处理方法研究

圆周合成孔径雷达(Circular Synthetic Aperture Radar,CSAR)因具有超高分辨率、三维成像能力、全方位信息获取等优势已经成为雷达领域的研究热点.在实际应用中,场景中目标通常仅在较小观测角度内具有近似恒定的散射特性.为此本文提出了一种基于子孔径划分的CSAR频域成像处理方法,该方法相比于时域成像处理具有更高的处理效率.文中给出了CSAR回波的频谱表达形式并深入分析了其特性;提出了CSAR子孔径频域成像处理的基本流程,理论上详细论证了文中所提算法的可行性.最后仿真试验证实了文中所提信号模型及成像处理流程的正确性.     

加速后向投影圆迹SAR成像方法

凭借多视角观测和高分辨成像的能力,圆迹合成孔径雷达（CSAR）受到了越来越多的关注。然而,特殊的运动轨迹和强烈的二维耦合给成像算法提出了挑战。以兼顾图像质量和运算效率为目标,本文提出了一种适用于CSAR成像的加速后向投影（EBP）算法。EBP算法将整个合成孔径划分为若干子孔径,使用全局极坐标系重建每幅子图像。根据角域波数域和方位时域的对应关系,EBP算法通过波数谱搬移实现波数谱融合,再经由二维逆傅里叶变换实现图像聚焦。EBP算法继承了后向投影（BP）算法的精确性和运动补偿优势,避免了插值操作引起的图像质量损失。最后,通过仿真实验验证该方法的有效性。      

基于改进PFA的车载大斜视SAR成像算法

为了应对车载毫米波雷达大斜视成像困难的问题,本文提出一种改进的极坐标格式算法（Polar Format Algorithm, PFA）对条带车载毫米波雷达斜视回波进行基于子孔径拼接的成像。该算法从条带数据与聚束数据的特点出发,将全孔径回波划分为子孔径,利用PFA处理子孔径数据。由于PFA存在波前弯曲误差,子图像不能直接拼接,因此对每一幅子图像进行几何失真校正。同时,以重叠子孔径的划分方式保证成像结果的高分辨率。最后截取子图像进行拼接得到条带SAR成像结果。所提方法解决了车载毫米波雷达大斜视情况下两维耦合严重的问题。通过对点目标和实测数据的仿真与分析验证了所提方法的有效性。     

子孔径NCS算法中虚假目标产生的机理与消除方法研究

子孔径结构的引入是实现Ultra Wide Band SAR(UWB SAR)实时信号处理的关键。将子孔径结构与Nonlinear Chirp Scaling(NCS)算法相结合的子孔径NCS算法可以较好的实现UWB SAR实时信号处理,但子孔径结构的引入使得成像结果中存在虚假目标的影响。针对子孔径NCS算法中存在虚假目标的现象,该文从理论上分析了虚假目标产生的机理,并提出了对距离弯曲校正前的子孔径回波两端补零的改进子孔径NCS算法消除虚假目标,最后通过仿真和实测的UWB SAR回波数据验证了该文理论分析以及所提方法的正确性。     

干涉圆迹SAR的目标三维重建方法研究

圆迹合成孔径雷达（CSAR）的360全方位观测能够获取目标各方向的散射特征,但是单轨迹圆迹SAR对于强方向性目标高度向散射特征的获取能力非常弱。该文针对典型目标开展3维圆迹SAR干涉方法研究,开展了基于暗室实验的原理性验证,首次给出了实际坦克金属模型的干涉圆迹SAR的3维重建结果,验证了该方法的有效性,同时展示了3维重建与全方位观测相结合在目标精细特征描述方面具有的重要应用潜力。      

基于BP和CS相结合的圆周SAR三维成像算法

与传统的直线SAR相比,圆周SAR(CSAR)具有对场景进行三维成像的能力,但对于一般的目标,其有效孔径只是一定角度的圆弧而非完整圆周孔径,使得圆周SAR只能获得航迹向和斜距向的高分辨率,影响了其三维成像能力,所以现在通常采用沿着不同高度角进行多次观测的多航过圆周SAR模式来实现三维成像。针对多航过圆周SAR由于多航过稀疏并且非均匀采样而严重影响成像质量的问题,提出一种将BP算法和压缩传感算法(CS)结合的三维成像算法。该算法先利用BP算法实现每一次航过数据的二维成像,再利用压缩传感算法进行高度向聚焦,来改善高度向的聚焦质量,最后将实测数据成像结果和传统的三维BP算法的结果进行比较,证明该算法可以有效地抑制旁瓣,得到超分辨的三维成像结果。     

压缩感知理论在探地雷达三维成像中的应用

该文基于探地雷达成像目标空间的稀疏特性,提出了探地雷达中的随机孔径压缩感知3维成像方法,该方法在单道数据获取中应用压缩感知减少采集数据量的同时,在x-y测量平面上随机抽取部分孔径位置进行测量,以少量的测量孔径和测量数据获得重建目标空间的足够信息,同时该文研究了噪声以及测量矩阵对算法性能的影响。结果表明,随机孔径压缩感知成像算法比传统后向投影算法所需数据量少,成像效果好,目标旁瓣小,对噪声的鲁棒性更好。     

圆迹SAR极坐标格式算法研究

 该文提出一种新的用于圆迹合成孔径雷达(Circular Synthetic Aperture Radar, CSAR)成像的极坐标格式算法。在CSAR模式下,点目标的波数域3维频谱为3维曲面。根据这一特点,算法采用逐高度平面成像的方法最终获得3维图像,即通过参考函数相乘,将频谱投影到2维平面,既避免了高度向的插值,又保证了算法的精确性。并且该算法通过两步相位补偿操作校正了越距离单元徙动的高次项,扩大了有效成像范围,避免了场景边缘目标的散焦。最后,点目标仿真验证了该算法的有效性。     

基于交互多模型的机载雷达高度滤波算法

机载三坐标雷达系统中,受雷达孔径的限制,俯仰方位的测角精度较差。为了获取目标在俯仰位置的精确信息,提出了基于交互多模型的机载雷达高度滤波算法。该算法先计算目标的地理高度,再采用基于匀速运动与当前统计(CS)模型的交互多模型滤波算法对目标的地理高度进行滤波。仿真结果表明:该算法在目标高度机动与非机动情况下均能有效跟踪目标高度变化,具有较好的适应性与滤波精度。     

直接基于目标距离环杂波特性的样本选择

提出了一种基于CUT杂波特性直接估计的机载雷达训练样本选择算法。该方法直接利用CUT的子孔径协方差矩阵对杂波进行表征,由于估计过程不依赖训练样本,可不受样本中干扰目标影响。考虑到目标距离环中可能存在目标信号,所提算法采用CUT子孔径协方差矩阵的Capon谱对目标可能存在的区域以外进行积分重构,从而剔除协方差矩阵中的目标成分。相比于传统广义内积算法利用单拍数据计算检验统计量,基于CUT杂波特性直接估计算法以样本的子孔径协方差矩阵表征其特性,可使计算结果更加稳定。通过仿真实验表明,所提算法在筛选训练样本时更加准确。     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.     

GaAsSb/InAlAs PA DHBTs Grown by Production MBE

The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO＞6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.     

Technology innovation and process integrations for sub-100nm gate patterning

This paper presents a brief overview of the Applied Centura(R)DPS(R)system,configured with silicon etch DPS Ⅱ chamber, with emphasis on discussing tuning capability for CD uniformity control. It also presents the studies of etch process chemistry and film integration impact for an overall successful gate patterning development. Discussions will focus on resolutions to key issues, such as CD uniformity, line-edge roughness, and multilayer film etching integration.     

White organic light-emitting devices based on fac tris（2- phenylpyridine） iridium sensitized 5,6,11,12-tetraphenylnap -hthacene

We have fabricated the white organic light-emitting devices （WOLEDs） based on 4,4＇ -bis（2,2 -diphenyl vinyl）-1,1＇ - biphenyl （DPVBi） and phosphorescence sensitized 5,6,11,12,-tetraphenylnaphthacene （rubrene）. The device structure is ITO/2T-NATA （20 nm）/NPBX （20 nm）/CBP： x%Ir（ppy）3：0.5% rubrene （8 nm）/NPBX （5 nm）/DPVBi （30 nm）/Alq（30 nm）/LiF（0.5 nm）/A1. In the devices, DPVBi acts as a blue light-emitting layer, the rubrene is sensitized by a phosphorescent material, fac tris （2-phenylpyridine） iridium [Ir（ppy）3], acts as a yellow light-emitting layer, and N,N＇ -bis- （1-naphthyl）- N,N＇ -diphenyl -1, 1＇ -biphenyl-4,4＇ -diamine （NPBX） acts as a hole transporting and exciton blocker layer, respectively. When the concentration of Ir （PPY）3 is 6wt%, the maximum luminance is 24960 cd/m^2 at an applied voltage of 15 V, and the maximum luminous efficiency is 5.17 cd/A at an applied voltage of 8 V.     

Complete approach to automatic identification and subpixel center location for ellipse feature

To meet the need of automatic image features extraction with high precision in visual inspection, a complete approach to automatic identification and sub-pixel center location for similar-ellipse feature is proposed. In the method, the feature area is identified automatically based on the edge attribute, and the sub-pixel center location is accomplished with the leastsquare algorithm. It shows that the method is valid, practical, and has high precision by experiment. Meanwhile this method can meet the need of instrumentation of visual inspection because of easy realization and without man-machine interaction.     

小角度扩展相关性近似算法分析

本论文提出一种在多天线MIMO信道相关性建模中小角度扩展近似理论算法,并应用于分析MIMO系统性能。分析中分别对三种不同角能量分布情况下的空间相关性研发快速近似计算法,并同时提出双模(Bi-Modal)角能量分布情况下的近似运算。通过分析这些新方法的近似效率,可以得到计算简单、复杂度低、而且符合实际的MIMO相关信道矩阵,对系统级的快速高效计算法的研究和系统级的评估以及误差分析具有重要的意义。     

Noise character analysis and the restraint of self-pulsation laser diodes

We calculate the Langevin noise sources of self-pulsation laser diodes, analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation, and propose a novel method to restrain the noise effects. A visible SIMULINK model is established to simulate the system, The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current, the noise effects enhance power jitter, and nevertheless, the period jitter is decreased; and that with external sinusoidal current modulating the self-pulsation laser diode, the noise-induced power jitter and period jitter can be suppressed greatly. This work is valuable for clock recovery in all-optical network.