MIMO雷达中的谱修正旁瓣抑制技术研究

谱修正是一种简单有效的抑制脉压旁瓣的方法,通过对信号的频谱整形,抑制信号带内起伏,并采用频域加窗达到控制脉压信号距离旁瓣的目的。MIMO雷达常用的正交信号经脉冲压缩后存在不希望的距离旁瓣,若直接将谱修正技术用于MIMO雷达各个子带信号脉压处理,由于子带间信号互相关的影响,将不能获得较好的距离旁瓣抑制效果。本文针对该问题,提出了一种对MIMO雷达综合信号进行谱修正和频域加窗的方法,可以更有效地抑制脉压距离旁瓣。仿真结果显示,该方法能取得40dB以上的主副比,且能有效降低系统的复杂度和运算量,在多普勒和角度偏差不大的情况下,其峰值旁瓣电平明显低于传统的匹配滤波。      

FD-MIMO距离高分辨雷达及其旁瓣抑制

为了提高距离分辨率而又不增加对发射/接收机带宽的要求,该文提出了频分多入多出(Frequency-Divided Multiple Input Multiple Output,FD-MIMO)雷达。该雷达利用同时发射的多路窄带信号合成宽带波形,进而得到目标的高分辨距离像。由于持续时间短,合成高分辨距离像具有很好的多普勒容限。此外,针对由合成频谱不连续性造成的近区高旁瓣和由子带间耦合造成的远区高旁瓣,该文分别提出使用倒数谱滤波器和对子带信号加带外衰减的方法予以抑制。最后,理论分析和数值仿真证明了旁瓣抑制方法的有效性。     

MIMO探地雷达随机步进频信号旁瓣抑制

针对MIMO探地雷达中随机步进频信号的距离旁瓣较高的问题,提出了一种基于快速二阶锥优化问题的旁瓣抑制方法。该方法首先通过建立随机步进频信号模型对回波信号进行预处理,然后基于回波信号的旁瓣特点将旁瓣抑制问题转化为以信号的峰值旁瓣构建目标函数,以主峰损失、峰值旁瓣和积分旁瓣联合约束的二阶锥优化问题,最后使用内点法求解二阶锥规划问题,以此得到最优的旁瓣滤波器系数。仿真和实测数据处理结果表明,设计的失配滤波器能够在较低主峰损耗的情况下,有效降低峰值旁瓣电平和积分旁瓣电平,提高信号的主旁瓣比。该方法为MIMO探地雷达中的距离旁瓣问题提供了有效解决思路,有望在工程应用中提高探地雷达的性能。     

OFDM雷达通信共享信号距离旁瓣抑制研究

在采用自适应调制技术的正交频分复用（OFDM）雷达通信一体化系统中,共享信号通常具有非矩形且变化的功率谱,这导致传统旁瓣抑制方法出现主旁瓣比降低及信噪比损失增加等问题。针对该情况,提出了一种新的OFDM共享信号距离旁瓣抑制方法,根据发射信号功率谱自适应设计幅度加权函数,将旁瓣抑制问题转化为优化问题求解。仿真结果表明,该方法在发射信号频谱变化甚至断续的情况下,都能有效抑制OFDM共享信号的距离旁瓣,且具有远小于常规方法的信噪比损失。      

非连续谱FMCW雷达信号分析与处理

高频地波雷达工作在干扰严重的高频段,系统很难找到一段连续寂净的工作频段.为提高雷达抗干扰性能,用几个不连续的干净频带来合成系统的有效带宽.分析了一种非连续谱线性调频雷达信号;根据信号特点采用先速度后距离的二维处理方式;通过对每段信号进行分解、相位补偿、重构的方法来消除由频率跳变所引起的距离旁瓣增高,谱峰分裂、偏移等影响.仿真结果表明了该方法能有效地抑制旁瓣,实现目标的二维分辨.     

基于交替投影的MIMO雷达最优波形设计

该文研究用于多输入多输出(MIMO)雷达的具有低相关旁瓣的恒模波形设计方法,这类波形可以抑制距离旁瓣遮蔽和不同信号回波之间的相互干扰。首先,根据非周期相关函数与功率谱(PSD)之间的傅里叶变换对关系,将波形的相关特性优化问题转换为功率谱优化问题;然后,基于功率谱拟合的思想,将设计波形的功率谱向理想波形功率谱逼近;最后,在时、频域交替投影的算法框架下,利用快速傅里叶变换(FFT)实现波形的优化设计。计算机仿真表明,该算法能够设计具有良好相关特性的MIMO雷达波形且运算效率较高。     

准随机跳频信号的二维处理

高频雷达工作的波段十分拥挤,因而可用的连续带宽比较窄,雷达获得距离分辨力极为有限.为避开干扰频段能够提高系统带宽,本文采用了一种频带不连续的准随机跳频信号.并根据信号的特点,系统地提出了该信号的二维信号处理方案.仿真表明,这种方案具有解距离-速度模糊的能力,能有效地抑制最大距离旁瓣,较好地实现了距离速度二维分辨.     

基于完全互补码波形的非零多普勒目标检测

本文将完全互补码(Complete Complementary Code, CCC)应用于多输入多输出(Multiple Input Multiple Output, MIMO)雷达目标探测中，针对具有非零多普勒的多目标检测问题，提出一种基于广义普洛黑-修-莫尔斯(Generalized Prouhet-Thue-Morse, GPTM)序列和二项式系数加权的信号处理方法。该方法分别在发射端和接收端进行处理，在发射端采用GPTM序列设计方法调整脉冲的发射顺序，以降低由多普勒引起的距离旁瓣；在接收端通过二项式设计(Binomial Design, BD)方法为各接收脉冲加上不同权重，扩大目标多普勒附近的清洁区。为综合上述两次处理的优势，将两次处理得到的距离多普勒谱进行逐点最小化处理，得到最终的距离多普勒谱，然后进行有序恒虚警检测。仿真结果表明，本文所提的信号处理方法具有良好的旁瓣抑制效果和多普勒分辨率，能够有效检测出非零多普勒目标。     

多载频MIMO雷达的一种新的信号处理方法

多载频MIMO雷达(Multi-Carrier MIMO radar)是指利用频率分集和空间分集的方法来实现发射信号正交的具有多个发射和多个接收天线的雷达系统,该文研究了该体制雷达基于Dechirp处理实现距离高分辨的方法,分析了IFFT相参合成法以及伪峰产生原因,提出了一种新的处理方法空域合成带宽法,它将空域分散发射的多载频LFM信号,先做Dechirp处理,然后再将通道分离后的各路信号顺序时移拼接合成一个大带宽的LFM信号,最后再对合成后的信号做IFFT处理以获得高分辨距离信息。它实现简单,能够在不增加运算量的条件下有效的抑制伪峰,并受目标运动影响小,计算机仿真验证了这些结论。     

发射分集MIMO雷达融合成像处理方法

发射分集MIMO雷达具有潜在的高分辨成像能力,但成像时存在高旁瓣问题。为分析它的成像性能,该文首先建立了发射分集MIMO雷达的成像模型。通过空间频谱的支撑区分布,阐明了分集成像的高分辨性能,并着重分析了其旁瓣特性。基于谱外推的思想,提出了一种发射分集MIMO雷达融合成像处理方法,该方法能够实现MIMO雷达高分辨成像同时具有良好的旁瓣性能。仿真实验验证了该文所提方法的有效性。     

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.     

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.     

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.     

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.     

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.