基于盲源分离的CDMA系统信息码与扩频码盲估计

针对码分多(CDMA)系统盲多用户检测问题,提出了一种基于盲源分离(BSS)的信息码盲检测与扩频码盲估计算法.该算法在对CDMA系统进行多用户检测的过程中,不仅不需要知道用户的扩频码,同时利用最小均方误差(MMSE) 则还可以盲估计出不同用户的扩频码序列.仿真结果证明该算法有较大的实用价值.     

基于虚拟多用户模型的长码直扩信号伪码估计

针对长码直接序列扩频(DSSS)信号的伪随机码(PN)盲估计问题,提出了一种新的周期长码直接序列扩频信号(PLC DSSS)模型.该模型等同于虚拟多用户短码扩频DS - CDMA系统,采用DS- CDMA的谱范数来估计同步偏移,该算法不需要更多假定限制,利用相关函数二阶矩、特征值分解和模糊酉矩阵方法就可以完成伪码序列的...     

基于改进FastICA的多用户检测

研究了直接序列扩频码分多址(DS-CDMA)通信系统的多用户检测问题,利用DS-CDMA信号中各用户扩频码和用户信息数据统计独立性建立了基于独立分量分析方法的多用户检测模型,通过对噪声作白化预处理,对FastICA算法的分离性能进行分析并给出精度修正矩阵,提出了一种改进FastICA的多用户检测算法.仿真结果表明,该方法较传统检测算法具有更好的检测性能、更强的抗多址干扰的能力和抗远近效应的性能.     

码分多址通信系统多用户检测的仿真研究

多用户检测技术利用各个用户的扩频序列、时延、幅度和相位信息对各用户进行联合检测,能有效抑制多址干扰,充分利用上行链路频谱资源,提高系统性能和容量,是码分多址通信系统中的关键技术之一。文章采用基于卷积编码块的串行干扰抵消多用户检测方法,利用MATLAB对多用户检测算法进行仿真,通过研究不同数据速率的三种应用场景,验证多用户检测算法对参考用户误码率的性能改善和提高系统用户容量的有效性。     

基于快速OPAST算法的直扩信号PN码序列估计

在直接序列扩频(DSSS)通信对抗系统中,伪码(PN)序列估计是一个重要的研究课题.针对在某些情况下权值向量不收敛的问题,提出了一种基于快速正交投影逼近子空间跟踪(OPAST)算法和滑动窗技术的直扩信号PN码序列估计算法,对非同步接收DSSS信号按照宽窗口分段,利用快速OPAST算法提取主特征向量,滑动窗技术实现码同步.该算法迭代权值向量具有正交性以及良好的收敛性,同时解决了常见相位模糊问题.算法具有较低复杂度,数据存储量少,易于硬件实现与实时处理.仿真结果表明,在-10 dB的较低信噪比背景环境中,该快速OPAST算法可以正确有效地估计出PN码序列.     

基于时空混沌的CPSK多用户扩频通信

传统的混沌扩频（CDSS）是利用混沌序列量化、编码后产生的0、1序列作为扩频码,来实现频谱展宽。另外,由于混沌序列本身的宽频特性,一些传统的混沌数字调制技术也可被用于扩频通信系统的设计。在单向耦合映像格子（OCML）时空混沌模型同步的基础上,直接利用混沌相位键控（CPSK）调制技术构建了一个多用户扩频通信系统。该模型为每个用户分配一个OCML时空混沌模型,为了更好地利用时空混沌系统的时间与空间混沌特性,其采用＂跳格序列＂作为扩频调制序列对用户信息进行调制。通过与传统混沌直接序列扩频（CDSS）系统的仿真比较发现,所设计的CPSK调制多用户扩频通信系统拥有比后者更好的误码性能及安全性能。     

异步多径条件下空时CDMA多用户检测

本文利用最小均方误差准则,推导了异步多径条件下空时CDMA多用户检测算法,分析了多用户检测与单用户检测关系,提出空时CDMA多用户检测接收机结构。基于SAGE迭代算法进行空时多用户检测,并利用CDMA信号的有限字符特性和上行信道的导频信息对SAGE算法提出改进。仿真结果说明了本文提出的空时CDMA多用户检测算法性能。     

一种盲自适应空时多用户检测技术

空时多用户检测技术是一种有效消除CDMA系统中多址干扰和码间干扰的方法。目前很多此类方法都需要知道一些系统参数,其自适应实现需要训练序列。提出了一种结合恒模算法(CMA)和解扩重扩算法(DRA)的盲自适应空时恒模解扩重扩算法(STCMDRA),他能够有效利用信号的恒模特性以及用户已知的扩频信号信息来较好地抑制多址干扰及码间干扰。仿真结果进一步验证了该方法的性能。     

伪随机码的盲信源分离方法

根据伪噪声通信及伪随机码的相关特性,提出一种采用盲信源分离方法从伪码扩频信号中分离不同伪码序列的方法,并探讨该方法在CDMA监听系统中的应用。采用该分离方法能快速准确地分离和识别不同用户的伪码特征,来获得该用户的语音或数据信息,具有很好的应用前景。     

基于Fast-ICA同、异步系统短码CDMA信号扩频序列与信息序列盲估计

本文通过分析短码CDMA信号特性,将接收信号以间隔2倍扩频周期、重叠1倍扩频周期的时间窗进行分割,建模CDMA系统与线性混合的盲源分离模型一致,使建立的CDMA模型同时适用于同、异步系统.利用盲源分离方法,实现了同步系统、异步系统失步时间未知和已知条件下,各用户等功率或非等功率时,扩频序列与信息序列的盲估计.理论分析和...     

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.     

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.