基于决策论的数字调制信号识别方法

以决策论为基础提出了一种改进的数字调制信号识别方法,该方法仅需4个相对简单的特征参数,就能识别2ASK、4ASK、2FSK、4FSK、2PSK、4PSK和16QAM这7种数字调制信号。仿真结果表明,该方法复杂度较低,识别正确率有较大提高,尤其对于2ASK、4ASK、MPSK/MFSK及16QAM的识别,在信噪比较低的情况下,具有较好的识别效果。     

基于高阶累积量和循环谱的信号调制方式混合识别算法

为了识别当前通信系统所采用的主要调制方式,该文结合高阶累积量和循环谱的特点,采用混合识别算法,同时应用智能决策算法(神经网络)对信号进行识别。该算法基于四阶和六阶高阶累积量构造出一个新的特征参数,将数字调制信号分为{BPSK, 2ASK}, {QPSK}, {2FSK, 4FSK}, {MSK}和{16QAM, 64QAM}5类。然后利用高阶累积量的其它特征参数以及循环谱特征对{OFDM}, {16QAM, 64QAM}, {2ASK, BPSK}及{2FSK, 4FSK}进行识别。为便于工程实现,该文采用半实物仿真以及LabVIEW和MATLAB混合编程来验证算法。仿真结果证明,该算法能够在较低信噪比下实现对{OFDM, BPSK, QPSK, 2ASK, 2FSK, 4FSK, MSK, 16QAM, 64QAM}等多种信号的分类,在信噪比高于 5 dB时,调制方式识别率可达94%以上,由此证明了该方法的有效性。     

高阶累积量和分形理论在信号调制识别中的应用研究

提出了将信号高阶累积量和分形盒维数相结合的特征提取方法。信号高阶累积量特征具有良好的抗噪性能,被广泛应用于调制识别。2ASK和BPSK的高阶累积量、以及2FSK,4FSK,8FSK的高阶累积量相等,使得只提取信号高阶累积量不足以区分信号。针对这一问题,引入信号的分形盒维数,提取信号的高阶累积量和分形盒维数构成联合特征参数,构建级联神经网络分类器,对信号进一步进行分类。对2ASK, 4ASK, BPSK, 4PSK, 2FSK, 4FSK, 16QAM七种信号进行了仿真,结果表明,该方法提取的特征参数计算复杂度低,具有较好的抗噪性能。在信噪比不低于5dB、测试样本数不少于200的条件下,正确识别率达到了85%以上。      

基于高阶累积量的数字调制信号检测与识别方法

通信信号调制方式识别在信号检测、频谱监测等领域有着重要的地位,是非合作通信的关键技术.本文利用信号的四阶、六阶、八阶累积量构造多个特征参数,实现了2ASK、2FSK、BPSK、QPSK、16QAM和OFDM六种常用数字信号调制方式的识别.在MATLAB环境下进行了仿真实验,实验结果表明,该方法在0dB信噪比下可以实现有...     

特征提取及其在数字调制方式识别中的应用

通信信号调制识别技术在军事和民用领域都具有重要的应用前景,而特征参数的提取是调制方式识别的首要问题。本文提出了两个新的特征参数,并结合这两个新的特征参数在统计模式识别的基础上构造了一组新的特征集参数,该特征集无需任何先验知识。随后,本文针对2PSK、QPSK、8PSK、16QAM、2FSK、4FSK、8FSK、2ASK、4ASK等9种调制类型,采用了分层结构的神经网络分类器进行自动识别。大量仿真表明,在待识别的信号信噪比大于5dB时,该识别系统的正确识别率达97%以上,且识别的稳定性好。     

基于循环谱和高阶累积量的联合模式识别方法

为完全识别当前卫星通信采用的主要调制方式,结合循环谱和高阶累积量两种信号调制识别方法的特点,提出了一种联合识别算法。该算法将循环谱特征加入到高阶累积量识别法中,联合多种特征参数判决构建识别器,首先利用循环谱完成ASK、FSK、PSK信号的类间识别以及FSK信号的类内识别,在此基础上利用高阶累积量方法完成FSK、PSK信号的类内识别。仿真结果表明,该算法能够完全区分卫星通信中主要的调制模式{ASK、2ASK、2FSK、4FSK、BPSK、QPSK},在信噪比高于5 d B时识别率达88%以上。     

小波分析与最小二乘支撑矢量机在调制识别中的应用

自动调制识别是通信对抗及软件无线电等领域的一个重要研究课题。本文提出了一种使用小波分析与最小二乘支撑矢量机,对数字调制信号的识别方法。首先对接收到的信号进行小波去噪,然后提取其小波包分解系数模值的标准方差作为识别的特征参数．利用最小二乘支撑矢量机为分类器,对2ASK,4ASK,2PSK．4PSK．8PSK．4QAM,16QAM．2FSK和4FSK九类数字信号进行分类识别。计算机仿真结果表明该方法有效．在信噪比为0dB时正确识别率达到99．01％。     

利用高阶累积量实现数字调制信号的自动识别

通信信号的自动调制识别在截获信号处理方面是一个十分重要的课题。本文针对数字调制信号的识别问题,提出了一种基于高阶累积量的分类特征,该特征有效地抑制高斯白噪声的影响,能实现对2ASK、4ASK、4PSK、2FSK、4FSK等五种数字调制信号的识别。论文进行了理论推导,并用仿真实验和实际采集数据进行了验证。     

基于累积量和SVM的数字调制识别

文中提出了一种基于高阶累积量和支持向量机的数字调制信号识别新算法,即从信号的四阶和六阶累积量中提取的参数作为分类特征向量,利用基于二叉树的支持向量机作为分类器的方法实现了2ASK、4ASK、8ASK、4PSK、8PSK等五种数字调制信号的识别。仿真结果表明,在信噪比为10dB情况下,该算法的正确识别率达到了95.83%以上。     

通信系统中调制类型自动识别方法分析

根据接收信号样本提取出振幅、频率和相位的特征参数,在AWGN信道中,采用小波变化的方法,针对接收信号样本中提取出的振幅、频率和相位的特征参数,设计调制类型自动识别,对幅度调制和非幅度调制信号特征参数分析,对QAM、ASK、PSK和FSK调制信号的特征参数进行分析,并对区分调制信号的关键参数进行分析并确定,通过对仿真结果的对比表明能实现调制信号的正确识别。     

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.