一种快速的二相编码信号检测算法

相位编码信号雷达因为其抗干扰能力以及低截获概率特性而得到了广泛的应用。提出一种新的相位编码信号检测算法,实现了对相位编码信号的特征提取,根据频率构造正弦信号,利用相参检波实现二相编码信号的解码。该算法在信噪比为0 dB时仍然可以对编码信号进行准确的调制特征分析。     

基于Golay脉冲编码技术的相干激光雷达仿真研究

针对相干激光雷达远场回波信号信噪比低,提取困难的问题,提出了脉冲编码技术,以改善系统信噪比,增大雷达探测距离。研究了相干激光雷达系统中Golay码的编码和解码原理,理论分析了采用脉冲编码技术对系统信噪比的提升效果。基于大气分层模型仿真生成了相干激光雷达时域回波信号。基于Golay码解码原理得到了脉冲编码系统的风速结果,仿真结果表明,时间分辨率为1s,距离分辨率为60m的情况下,使用Golay编码脉冲作为相干激光雷达的探测脉冲,在0~5.3km范围,风速误差小于3m·s~(-1)。在相同的测量时间内,相比于传统脉冲相干激光雷达,基于脉冲编码技术的相干激光雷达将探测距离提高了2.5km,提高了远场弱信号的信噪比。     

一种低信噪比二相编码信号时频分析方法

针对时频分析方法在低信噪比条件下识别二相编码信号相位突变点效果较差的问题,提出了一种在低信噪比条件下的相位编码信号相位突变点检测的新方法.新方法首先估计信号的载频,然后得到信号载频处STFT变换的幅值矩阵,设定合适的阈值后进行积累运算,最后再设置一定的阈值检测出相位突变点的位置.仿真结果表明新方法有效可行,能够在更低的信噪比条件下准确检测出信号的相位突变点位置.     

一种基于APPA的码辅助载波同步算法

在低信噪比环境下,小的频偏和相偏的存在会使Turbo编码系统的译码性能恶化,所以必须结合迭代译码系统,对信号的残留频偏和相差进行估计。该文提出一种改进的残留频偏载波相位估计算法后验概率辅助(APPA)相位估计,该算法将译码器输出的外信息用于辅助迭代的相位估计。环路滤波器将相位误差信号转换成控制信号,控制数控振荡器的输出,这样可以得到待估计的相位误差。仿真表明,在极低信噪比下(比如,SNR-7.8 dB)该算法在同时存在频偏和相偏的时候能正常工作,其性能非常接近理想同步条件下的性能。     

对相位编码信号的部分相关检测

根据二相编码信号在相位突跳点两侧具有反相特性,提出一种二相编码解调方法：利用构造的相位突跳点样本,对各突跳点完成相关检测,并可在此基础上对编码进行重构。相关处理所具有的增益使得该方法可应用于对信噪比较低的相位编码信号的侦察。     

线性调频相位编码混合调制信号及其DDS实现

利用线性调频信号、二相编码以及伪随机序列—巴克码构成一种线性调频相位编码混合调制信号,这种信号兼备了线性调频信号、二相编码和伪随机序列各自的特点,具有较好的反侦察特点,压缩后能够较大改善信噪比。本文给出利用DDS芯片AD9854实现这种信号的电路方法。     

不同脉冲编码调制的BOTDA系统性能分析与比较

研究了基于脉冲编码调制的布里渊光时域分析(BOTDA)系统原理,该系统向传感光纤注入经脉冲编码调制后的光脉冲序列,在接收端用数据处理程序恢复系统的单脉冲响应,从而提高BOTDA系统的信噪比、温度和应变分辨率.理论研究了BOTDA系统中Simplex码、Golay码和CCPONS码的编码和解码原理;利用Matlab仿真研究了不同脉冲编码调制的BOTDA系统的时域输出信号,并对比分析了三种编码对系统信噪比的改善情况,结果表明采用脉冲编码技术可使BOTDA系统性能得到有效提升,CCPONS码调制时可获得最佳系统性能,Simplex码次之.     

相位编码信号码速率估计的最优小波尺度选择

研究了小波变换应用于相位编码信号码速率估计的尺度选择问题,提出了一种最优小波尺度选择方法。以相位跳变的最佳检测为依据建立了最优小波尺度选择函数,然后结合功率谱平滑载频估计和信号编码形式完成最优小波尺度的选取,最后通过叠加模值频谱完成信号码速率估计。仿真实验表明,所提出的尺度选择方法将二相编码信号和四相编码信号的码速率估计信噪比门限分别降低了1 dB和3 dB。     

APD检测Golay编码BOTDR系统的建模分析与优化设计

针对传统单脉冲布里渊光时域反射系统信号微弱、性能提升受限的问题,提出了一种雪崩光电二极管（APD）检测器本地外差检测的格雷（Golay）编码布里渊光时域反射系统。分析了Golay码应用于该系统的编解码原理及系统外差检测原理,讨论了光纤受激布里渊散射阈值对编码系统平均入纤功率的限制,推导了系统信噪比的数学表达式,研究系统信噪比与APD倍增因子、编码长度的关系,分别得到了APD最佳倍增因子和系统最佳编码长度的表达式。MATLAB仿真结果表明,选用带宽为500 MHz的APD光电检测器和峰值功率50 mW、脉冲宽度100 ns的入纤脉冲时,系统APD倍增因子和编码长度均存在最佳值,系统最佳编码长度的确定不仅依赖于系统的散粒噪声和热噪声功率,还由光纤受激布里渊散射阈值共同决定。经优化计算得,该系统的APD最佳倍增因子为5,最佳编码长度为128位时,在25 km光纤末端的系统信噪比比传统单脉冲系统提高了26.42 dB,温度和应变分辨率分别达到了1.60℃和35.48。     

多载频混沌相位编码雷达信号处理研究

雷达波形设计与信号处理是现代雷达研究领域的热点。文中用具有弱结构性的混沌二相码对正交频分复用雷达信号的相位进行调制得到一种多载频混沌相位编码雷达信号,推导了该信号脉冲压缩的输出表达式,用分段FFT脉压法对该信号进行脉压,比较了该信号和多载频巴克码相位编码信号的脉压效果,并对该信号的接收处理过程进行了仿真。仿真结果表明:多载频混沌相位编码雷达信号具有更优异的脉压性能,能够实现在信噪比很低的情况下多目标的精确测距和测速,同时由于其灵活的结构、复杂的调制方式及类噪声的特性,提高了雷达的低截获性能。     

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.     

Nanoimprint Lithography -A Next Generation High Volume Lithography Technique

IntroductionNanoimprint Lithography is a well-acknowl-edged low cost, high resolution, large area pattern-ing process. It includes the most promising methods,high-pressure hot embossing lithography (HEL) [2],UV-cured imprinting (UV-NIL) [3] and micro contactprinting (m-CP, MCP) [4]. Curing of the imprintedstructures is either done by subsequent UV-lightexposure in the case of UV-NIL or by cooling downbelow the glass transition temperature of the ther-moplastic material in case of HEL…     

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.     

Influence of PVK ： NPB hole transporting layer on the characteristics of organic light-emitting devices

A doping system consisting of NPB and PVK is employed as a composite hole transporting layer （CHTL）. By adjusting the component ratio of the doping system, a series of devices with different concentration proportion of PVK ： NPB are constracted. The result shows that doping concentration of NPB enhances the competence of hole transporting ability, and modifies the recombination region of charge as well as affects the surface morphology of doped film. Optimum device with a maximum brightness of 7852 cd/m^2 and a power efficiency of 1.75 lm/W has been obtained by choosing a concentration proportion of PVK ： NPB at 1：3.     

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.     

Analysis of error performance on Turbo coded FDPIM

Due to variable symbol length of digital pulse interval modulation（DPIM）, it is difficult to analyze the error performances of Turbo coded DPIM. To solve this problem, a fixed-length digital pulse interval modulation（FDPIM） method is provided. The FDPIM modulation structure is introduced. The packet error rates of uncoded FDPIM are analyzed and compared with that of DPIM. Bit error rates of Turbo coded FDPIM are simulated based on three kinds of analytical models under weak turbulence channel. The results show that packet error rate of uncoded FDPIM is inferior to that of uncoded DPIM. However, FDPIM is easy to be implemented and easy to be combined, with Turbo code for soft-decision because of its fixed length. Besides, the introduction of Turbo code in this modulation can decrease the average power about 10 dBm, which means that it can improve the error performance of the system effectively.     

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.     

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.