直接序列扩频系统多音扫频干扰性能分析

为有效干扰直接扩频通信系统,通过分析扫频信号及多音信号在干扰直扩通信系统时存在的优缺点,提出了一种针对直扩通信系统的多音扫频干扰技术.该方法将直扩通信系统的频谱划分为若干个子频谱,针对每个子频谱采用扫频信号进行干扰.理论分析和仿真验证表明,该方法可以明显改善扫频干扰直扩通信系统时扫频时间过长以及多音干扰依赖音调位置的缺...     

采用压缩感知的直扩测控信号处理

鉴于扩频测控系统宽带化带来的高速采样压力和高数据率问题,研究了基于压缩感知的直扩测控信号处理方法。通过深入分析直扩测控信号稀疏性,构造了延时-多普勒基字典,提出了基于压缩感知直扩测控信号处理框架,并针对直扩测控信号特点给出了改进正交匹配追踪重构算法,最后针对该信号处理方法的可行性和性能分别进行了仿真实验。仿真结果不仅验证了方法的可行性,同时表明可以在不影响解调性能条件下大幅度降低采样率或数据率,并具有一定的降噪效果,这将为直扩测控通信系统提供一种高效的模数转换和同步解调处理方式。     

基于循环平稳差异的直扩信号盲提取抗干扰方法

提出一种基于循环平稳差异的直扩信号盲提取抗干扰方法.针对源信号在统计域上的近似独立性,构建直扩通信盲源分离抗干扰模型,基于源信号的循环平稳差异,利用循环自相关函数的典型极值点定义一个用于区分直扩信号和干扰的二阶循环差异度特征参数,通过比较该特征参数的大小进行模式识别,提取出直扩信号而抑制掉干扰,达到抗干扰的目的.仿真结果表明:当信干比(SJR)为-40dB、归一化信噪比(NSNR)为9dB时,直接解扩/解调信号的误比特率约为IE-0.3,而本文所提抗干扰算法误比特率(BER)低至IE-3,可从强干扰中有效分离并提取出直扩信号.     

基于信息辅助块稀疏贝叶斯学习的直扩通信窄带干扰抑制

现有基于Nyquist-Shannon采样定理的窄带干扰(Narrowband Interference,NBI)抑制方法存在应用受限于采样率较高的问题。应用压缩感知(Compressive Sensing,CS)理论解决上述问题,利用NBI在频域表现出的块稀疏特性以及直接序列扩频(Direct Sequence Spread Spectrum,DSSS)信号的类噪声特性,提出了基于块稀疏贝叶斯学习(Block Sparse Bayesian Learning,BSBL)框架的DSSS通信NBI抑制模型。实现干扰抑制后,利用传统的CS重构算法实现DSSS信号的压缩域解调。为进一步提高算法性能,将NBI稀疏分块的块内自相关矩阵建模为单位矩阵,提出了信息辅助BSBL(Aid BSBL,ABSBL)算法,设计了基于ABSBL的DSSS通信NBI抑制算法。该算法在保持较好NBI抑制性能的条件下,提高了运算效率并且不依赖NBI的稀疏结构。仿真验证和对比分析结果表明,所提方法能够有效抑制DSSS通信中的NBI,在干扰强度相同的条件下,NBI带宽越小、压缩率越大,算法对NBI的抑制性能越好。     

宽带压缩感知信号源个数估计算法

基于压缩感知的信号采集系统是目前宽带信号采集的重要发展方向,将其应用于通信侦查或频谱监测等宽带接收任务时,接收信号实际是处于宽带范围内的多个时域重叠的窄带信号,此时多分量压缩感知信号中的信源个数是后续信号处理的关键。本文针对调制信号在双频率平面具有稀疏性和可区分性,提出一种基于重构稀疏循环谱特征的信源个数估计算法。算法以重构误差的变化率作为迭代终止条件,应用改进的正交匹配追踪算法重构混合信号的循环谱,并应用循环谱的对称性实现信源个数估计。仿真表明,算法在-12dB条件下,信源个数估计准确率可以达到99%。      

压缩域直扩测控通信信号伪码跟踪方法研究

压缩感知理论已经在测控(TTC)通信相关领域有初步应用尝试,能够有效降低采样率和数据率,但同时其重构算法复杂度偏高、计算资源消耗过大,这与系统的实时性要求之间存在矛盾。论文基于直扩测控(DS TTC)通信信号稀疏性,对传统伪码跟踪环进行改进,提出一种基于随机解调压缩采样的压缩域伪码跟踪环。该环路不再需要进行信号重构处理,能够直接从直扩测控通信信号的压缩采样值中提取伪码(PN)延时相位信息。该文首先深入分析所提出环路模型及其鉴别特性,其次通过研究交叉噪声特性,对跟踪精度进行理论分析。分析和仿真结果表明,所提出环路能够在压缩域实现伪码延时相位跟踪。该环路可以应用在基于压缩感知的直扩、混扩信号处理等相关领域,具有一定工程应用价值。     

宽带直扩信号的随机解调压缩采样方法

为了有效解决扩频测控通信系统宽带化带来的高速采样压力和高数据率问题,提出了基于压缩感知的直扩信号随机解调压缩采样方法。通过对模拟信号压缩采样原理进行研究,深入分析和推导随机解调采样原理及其数学模型,提出了基于压缩感知的直扩信号采集系统构架,并对压缩比取值影响因素进行了分析;给出了随机解调压缩采样系统硬件实现方案,并对其可行性进行了分析;最后对所提出的直扩信号压缩采样方法的性能进行了仿真分析。仿真结果表明,压缩采样系统可以实现直扩信号的压缩采样处理,并能够高精度重构原信号,但重构信号的解调门限会随压缩比增大而相应提高,这是采样率降低所需付出的代价。压缩采样为宽带直扩测控通信系统提供了一种高效的模数转换和同步解调处理思路。     

基于加窗DFT的直扩通信系统窄带干扰抑制研究

针对直扩通信系统中基于门限检测的窄带干扰抑制的关键技术,引入重叠加窗方法,克服了由加窗带来的信号失真。并且提出了一种改进的自适应门限算法——归一化门限干扰检测处理算法。算法是将接收信号的包络经对数放大,归一化处理后得到一种归一化门限,然后将高于门限的谱线幅度抑制到与噪声相近的程度。分析和仿真表明,算法有较强的自适应能力,能有效抑制直扩系统中的窄带干扰。     

基于改进SVA和压缩感知的SAL旁瓣抑制算法

针对机载合成孔径激光雷达实测数据成像中旁瓣较高的问题,提出一种新旁瓣抑制算法。压缩感知理论表明,稀疏信号恢复重构过程的同时,信号旁瓣会被压低,但合成孔径激光雷达图像不是稀疏的。针对这一问题,提出了一种基于改进SVA（Spatially Variant Apodization）和压缩感知重构SAL图像的旁瓣抑制算法。首先,利用改进SVA算法将SAL图像变稀疏,然后再利用压缩感知算法对稀疏图像进行恢复。分别对SAL仿真数据和实际高旁瓣SAL复图像进行抑制旁瓣处理。仿真结果表明:该算法能够在保证主瓣不被展宽的前提下有效抑制SAL旁瓣。     

一种基于改进残差神经网络的直扩信号感知方法

非合作条件下直扩信号感知问题一直是通信对抗领域研究的热点，传统的感知方法在低信噪比条件下性能下降严重。为有效提升直扩信号感知的性能，提出了一种基于改进残差神经网络的直扩信号感知方法。首先，通过广义互相关算法，快速提取直扩信号的相关峰特性；然后，以残差神经网络为基础，融合注意力机制，建立网络模型，分析识别抽象特征；最后，在仿真的数据集中进行实验验证。结果表明，相较于时域自相关法、卷积神经网络法等，所提方法具备更好的感知效果，能够在信噪比为-16 dB的情形下有效地感知直扩信号。     

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.