基于OFDM技术的短波电台系统研究

OFDM（正交频分复用）技术是一种多载波数字调制技术,在无线多径衰落信道下具有较好的传输特性,文中设计短波电台系统采用了OFDM技术来对克服多径衰落带来的干扰,并且给出了系统的设计方案。利用Simulink建模,并在瑞利衰落信道和高斯信道下进行了仿真,结果显示出性能上有较大的改进。     

基于Simulink的OFDM系统仿真分析

无线衰落信道使得通信系统在传输过程中出现符号间干扰和信道间干扰,严重影响通信质量。正交频率分割复用(OFDM)是一种多载波数字调制技术,他在无线多径衰落信道下却具有较好的传输特性,对其抗多径衰落的原理进行了研究。在Simulink下建立了系统的仿真模型,并对所建模型进行了分析。同时在两径和六径瑞利衰落信道以及系统中有无交织下对其进行仿真,给出了仿真结果。     

一种新的自适应OFDM算法的探讨

在具有多径干扰的无线信道中仅应用传统OFDM既影响通信速率,也浪费资源.由于信道的频率选择性衰落,OFDM系统的每个子信道具有不同的传输能力.文中提出一种计算量较小、简单实用的自适应OFDM算法,在保证通信质量所需BER的前提下,按照各个子信道衰落程度动态的分配比特和功率,使所需要的发射总功率最小.仿真结果表明,采用该自适应OFDM算法可以提高OFDM系统的性能.     

一种基于OFDM的多载波通信系统的设计与仿真

OFDM(正交频分复用)是一种无线环境下的高速传输技术,它对由于无线信道的多径传播引起的ISI(符号间干扰)有很强的抵抗能力,已经引起了人们的广泛关注.文中首先介绍了OFDM技术的应用、发展以及基本原理,然后在计算机上用MATLAB对其性能进行了仿真,仿真中将OFDM与传统的单载波调制方式--16-QAM(正交幅度调制)对抗多径干扰的性能进行了比较,结果表明OFDM技术更适合于在有多径干扰存在的无线信道中传输.     

基于OFDM技术的视频传输研究

移动衰落信道中的图像传输已成为继移动数字话音通信迅速普及发展后的下一代通信的更高级通信形式。该文以OFDM技术为基础,重点研究了多径衰落信道中视频的传输问题。该文首先给出了确定保护间隔的原则,然后以此为基础对整个宽带无线视频传输系统进行了仿真分析。并且将仿真结果与QAM调制方式下的视频传输性能进行了比较,可以看出OFDM技术在实现宽带无线视频业务方面具有很高优越性。     

基于Vogler模型的短波OFDM性能仿真

OFDM(正交多载波调制)是一种在无线环境下具有较高频谱利用率的多载波调制技术,它具有较强的对抗多径干扰和消除符号间干扰的能力.基于Vogler模型出发,根据实测的短波信道参数数据进行了OFDM系统仿真,同时,用导频辅助的方法对信道进行估计,并进行信道补偿,克服了短波信道的多径衰落和多普勒频移等因素的影响,有效降低了系统的误码率,提高了整个系统的性能.     

基于OFDM技术的视频传输研究

移动衰落信道中的图像传输已成为继移动数字话音通信迅速普及发展后的下一代通信的更高级形式。该文以OFDM技术为基础重点研究了多径衰落信道中视频的传输问题。首先给出了确定保护间隔的原则,然后以此为基础对整个宽带无线视频传输系统进行了仿真分析。将仿真结果与OAM调制方式下的视频传输性能进行比较,可以看出OFDM技术在实现宽带无线视频业务方面具有很高优越性。     

无线信道中OFDM技术和QAM技术传输的性能差异

本文介绍了OFDM技术。OFDM是一种多载波调制技术，能够把有符号间干扰的信道转换成无符号间干扰的并行子信道，所以，OFDM技术能够有效的对抗信道的频率选择性衰落．它已经得到了广泛的应用。本文比较了语音文件在OFDM系统和QAM系统中的传输效果，得出在相同条件下OFDM调制要优于QAM调制的结论。     

可见光通信OFDM系统抗多径干扰性能研究

研究可见光通信OFDM系统在多径衰落信道中的传输性能.分别使用16-QAM和OFDM调制对声音和文本信源在多径衰落信道中进行传输,比较不同调制方式的传输效果.传输文本文件时,分析了误码率随衰落系数以及路径时延变化的关系.结果表明:可见光通信OFDM系统在多径衰落信道中传输,能克服多径效应,降低误码率,获得较为满意的通信质量.     

新一代宽带无线局域网系统中的OFDM技术研究

无线局域网是一种高速的无线数据传输系统,其调制技术的选择非常关键。OFDM(正交频分复用)是一种无线环境下的高速传输技术,适合在多径传播和多普勒频移的无线移动信道中传输高速数据。他能有效地对抗多径效应,消除符号间干扰,对抗频率选择性衰落,而且信道利用率高。文中对OFDM技术在新一代宽带无线局域网无线接入系统中的应用进行了分析和研究。     

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.     

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.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working.     

Call for Papers

正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks