基于超宽带信道的无线通用串行总线测试与分析

无线通用串行总线系统被视为下一代无线个人局域网通信的关键技术之一,并且被基于多频带正交频分复用技术的超宽带公共无线电平台进行标准化.文中对无线通用串行总线系统在超宽带通信信道中进行性能测试,其中使用了4个超宽带信道模型,每个模型使用100个现实通信信道.实验表明,无线通用串行总线系统在室内多径传输环境下能实现低速200 Mb/s 10 m和高速480 Mb/s 4 m的传输性能,达到了高速无线个人局域网技术的要求.     

室内VLC系统光源布局设计

在可见光通信系统中,光源具有照明和通信的双重作用,由于房间的大小以及室内环境各不相同,难免会存在光照射不到或者光线比较微弱的地方,这些地方很有可能成为通信的盲区,这将会大大影响通信的质量,为了解决阴影效应,需合理对光源进行布局设计,以4 m4 m3 m房间为模型,采用四个LED列阵作为室内光源,将单个的LED光源看做朗伯光源,服从朗伯辐射模型,通过公式计算结合软件仿真分析对比得出了采用99大小的LED列阵,列阵距离屋顶边缘0.4 m,LED光源间的间距为0.03 m时,在满足国际室内照明标准的前提下,在距离屋顶2.25 m的4 m4 m接收平面上光照度分布最均匀,其均匀度达到90.4%。该光源列阵布局模型可推广到任意尺寸房间,为室内办公照明中光源的布局提供了一种可行的方案。     

基于M—Power500的无线语音传输系统设计与实现

无线通信技术发展到今天,通信产品已经可以承载包括语音在内如数据、图像、动画以及多媒体等的其他业务,但语音通信仍然是最基本、最主要的通信方式。本文以MSP430F149单片机为控制核心,射频模块选用工作在2．4GHz频段的M-Power500,语音编解码芯片则选用CMX639来搭建一针对短距离通信的、全双工、低功耗的无线语音传输系统。经过测试,该系统在空旷的环境下,通信距离约200m,该设计实现了点对点无线对讲功能的预期目标。     

4G移动通信技术发展与关键核心技术研究

2012年1月18日,LTE-Advanced和Wireless MAN-Advanced(802.16m)技术规范被国际电信联盟确立为4G国际标准,由中国主导制定的TD-LTE-Advanced包含其中,这是我国通信事业的一大里程碑。本文主要介绍4G通信技术的发展历程,并对4G移动通信系统的网络结构和关键核心技术进行研究。     

基于虚拟仪器的任意m序列设计

论述了伪随机m序列的产生原理、特性以及构成方法,利用LabWindows/CVI为开发平台,设计了一种2~22级m序列发生器。仿真结果表明,该系统具有远程通信、界面友好、易于集成和扩展等优点,可实现无线激光通信系统误码率的自动化测试。     

日盲紫外LED实时视频传输系统设计

针对当前紫外光通信中气体灯与激光光源调制速率慢、体积较大,光电倍增管工作电压过高等问题,提出了一种基于现场可编程门阵列技术的日盲紫外LED实时视频传输系统,其发射光源采用波长为265 nm的单紫外LED,探测器采用紫外PIN;通过电路和逻辑模块设计搭建了视频传输系统,研究了系统的光功率密度与通信距离之间的关系;基于二进制开关键控调制方式,实现日盲紫外LED实时视频传输系统最大传输速率为2.88 Mbit/s,当通信距离为4 m时,传输速率达到1.92 Mbit/s。     

自适应光学技术提高FSO性能的实验验证

搭建了一套37单元的自适应光学系统和155M/2.5G大气激光通信系统室内实验平台。结果显示:大气湍流对激光通信性能影响很大。使用芯径为62.5μm的多模接收光纤时,自适应开闭环误码率最大改善超过4个数量级;使用芯径为10μm的单模接收光纤时,可以很明显地观测到接收端信号的深度衰落现象,且衰落程度与误码率一一对应。自适应光学闭环后,深度衰落得到了抑制,也极大地降低了系统误码率。     

一种基于直接序列扩频技术的矿井应急通信系统设计及仿真

采用扩频信号进行通信的优越性在于用扩展频谱的方法可以增大带宽来降低信噪比.在阐述扩展频谱通信技术的基本理论和实现方法的基础上,详细介绍了直接序列扩频以及伪随机码m序列原理、产生m序列的条件.继而提出了若干种矿井应急通信系统的具体设计方案,并利用MATLAB/Simulink软件平台对该系统进行了仿真及分析.结果表明,该...     

空间激光通信系统离轴天线设计研究

空间激光通信终端通常依靠光学天线提高整个通信系统的发射及接收效率。提出了一种空间激光通信系统的离轴天线系统,以克服传统卡塞格林两镜系统存在接收视场小、发射效率低等缺点。设计了一个通光孔径为150 mm,放大倍率为15,满足0.85、1.064、1.55 m多个通信波段光学天线系统。计算了初始结构参数,利用光学设计软件ZEMAX-EE对该光学天线系统进行了光线追迹和优化设计,并对设计结果进行分析。分析结果表明:在整个工作波段(0.85、1.064、1.55 m)内,点列图半径几何值小于10 rad,实现了高放大倍率、宽波段像散同时校正,在宽波段内均达到衍射极限,满足设计指标要求,能够满足高性能空间激光通信系统的要求。     

基于增益反馈控制的水下移动光通信技术研究

在水下移动可见光通信系统中,当传输距离改变时,因水具有较大固有吸收,接收光功率会发生显著变化。文章提出了一种基于增益反馈控制(GFC)的水下移动可见光通信技术,拓展了通信距离和视场角(FOV)的动态范围。在移动速度为0.13 m/s条件下,实现了通信距离0.9~5.2 m任意可调速率5.0 Mbit/s、像素为800×600且帧率(FPS)不为零的实时双工视频传输。与没有使用GFC方法的系统相比,其通信距离和FOV的动态范围分别增长了5.3和2.8倍。为了进一步验证该系统的性能,文章还测试了不同移动速度下系统的平均闪烁指数、数据传输中断概率及误码率(BER)。在通信距离的动态范围内,随着移动速度增大,平均闪烁指数及BER相应增大,但即使移动速度达到系统可实现的最大速度0.83 m/s时,通信仍未中断,说明该系统具有良好的鲁棒性,在水下移动可见光通信领域具有良好的应用前景。     

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.     

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.     

GaAsSb/InAlAs PA DHBTs Grown by Production MBE

The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO＞6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.     

Noise character analysis and the restraint of self-pulsation laser diodes

We calculate the Langevin noise sources of self-pulsation laser diodes, analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation, and propose a novel method to restrain the noise effects. A visible SIMULINK model is established to simulate the system, The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current, the noise effects enhance power jitter, and nevertheless, the period jitter is decreased; and that with external sinusoidal current modulating the self-pulsation laser diode, the noise-induced power jitter and period jitter can be suppressed greatly. This work is valuable for clock recovery in all-optical network.     

High-quality single-crystal CdSe nanoribbons and their optical properties

Large-scale synthesis of single-crystal CdSe nanoribbons is achieved by a modified thermal evaporation method, in which two-step-thermal-evaporation is used to control CdSe sources＇ evaporation. The synthesized CdSe nanoribbons are usually several micrometers in width, 50 nm in thickness, and tens to several hundred micrometers in length. Studies have shown that high-quality CdSe nanoribbons with regular shapes can be obtained by this method. Room-temperature photolumines-cence indicates that the lasing emission at 710 nm has been observed under optical pumping （266 nm） at power densities of 25-153 kW/cm^2. The full width half maximum （FWHM） of the lasing mode is 0.67 nm     

Propagation of hermite-cosh-gaussian beams passing through ABCD optical system with an annular aperture

By using the expansion of the aperture function into a finte sum of complex Gaussian functions, the corresponding analytical expressions of Hermite-cosh-Gaussian beams passing through annular apertured paraxially and symmetrically optical systems written in terms of ABCD matrix were derived, and they could reduce to the cases with squared aperture. In a similar way, the corresponding analytical expressions of cosh-Gaussian beams through annular apertured ABCD matrix were also given. The method could save more calculation time than that by using the diffraction integral formula directly.     

Influence of polarization extinction ratio on distributed polarization coupling detection

Distributed polarization coupling in polarization-maintaining fibers can be detected by using a white light Michelson interferometer. This technique usually requires that only one polarization mode is excited. However, in practical measurement, the injection polarization direction could not be exactly aligned to one of the principal axes of the PMF, so the influence of the polarization extinction ratio should be considered. Based on the polarization coupling theory, the influence of the incident polarization extinction on the measurement result is evaluated and analyzed, and a method for distributed polarization coupling detection is developed when both two orthogonal eigenmodes are excited.     

Call for Papers

正Communications—VLSI Researches and industries of telecommunications have been growing rapidly in the last 20 years and will keep their high growing pace in the next decade.The involved researches and developments cover mobile communications,highway and last-mile broadband communication,domain specific communications,and emerging D2D M2M communications.Radio communication steps into its