小口径固定站卫星天线自动寻星方案

为保证远端站卫星天线能够时刻对准卫星,中国移动应急通信网络的抗灾超级基站采用的小口径固定站天线采用了一种全新的自动寻星方案.该自动寻星天线系统在普通小口径固定站手动卫星天线的基础上,借鉴大口径电动天线、车载静中通、便携式卫星天线的传动系统及伺服控制的经验,通过改变天线传动系统和定制伺服控制系统来实现自动寻星功能,同时又...     

高通量卫星网络动中通用户站越区切换技术

针对高通量卫星多点波束组网下动中通站型跨波束、跨信关站以及跨星切换中存在的影响通信质量的问题,研究了可行的切换实现方案,提升了用户使用时的质量.在动中通应用场景中,用户站基于地理位置信息发起越区切换,介绍了越区切换解决方案,采用了信关站结合信号质量和目的波束资源分配情况进行切换控制的方法,对切换过程中的通信质量保障技术...     

卫星通信点波束覆盖算法研究

由于点波束的覆盖区域有限,针对与移动目标通信的情况,需要不停地改变卫星点波束的中心指向,以确保通信目标在点波束覆盖范围之内.卫星点波束的中心指向已知时,需要计算点波束对地球覆盖的区域,才能判断覆盖目标是否在点波束的覆盖区域内.根据上述工程应用的需求,提出了一种新的更易于实现的点波束覆盖区域算法.     

宽带卫星网络用户的移动性研究

Ka宽带卫星通信系统中,点波束和频率复用技术的应用可以大幅提高系统容量,但是机载、车载用户在不同波束间移动时会面临越区切换的问题。为实现对用户移动性的管理,结合Ka宽带卫星通信网络特点,借鉴地面网络的移动IP技术,提出了一种适用于卫星网络的移动性管理机制。该机制采用双向隧道封装技术,实现移动用户在不同波束之间、信关站之间移动时IP业务的高效传输。基于OPNET建模仿真结果表明,这种机制能够保证用户移动过程中IP业务传输不中断,解决了卫星多波束网络中用户移动性管理的问题。     

GEO卫星波束指向地面轨迹的计算与应用

由于受到各种空间因素的影响,GEO卫星通常工作在小倾角轨道,通过姿态偏置控制可以维持卫星多波束天线的中心视轴对地指向点固定,但除视轴外的其他波束中心以天为单位,进行周期性移动,在工程中会造成地面站指向偏移,影响卫星多波束资源的使用。通过理论分析与公式推导,给出了卫星多波束天线中任意波束中心指向地面轨迹的解算过程,并对其进行了仿真计算与分析,可以作为实际工程应用的理论参考。     

E1数据时隙插入与提取的实现研究

E1网络可靠性高,应用广泛,卫星调制解调器中,E1接口的设计具有重要的意义,并可扩展到其他应用场合。E1接口芯片采用的是DS21354,该芯片主要实现数据编解码、数据/时钟恢复,波形成型以及帧定位功能,芯片配置由单片机完成。为了解决远端站与中心局之间的传输需求,提供了提取和插入功能,该操作用FPGA实现,通过单片机可选择性地调节提取和插入的时隙,使用了乒乓操作和FIFO来完成该功能。     

海事五代卫星通信系统关键技术分析

针对国际移动卫星通信公司最新一代的卫星移动通信系统——海事五代卫星通信系统在Ka频段雨衰严重的问题,分析了关口站冗余配置技术;对系统中为了提高通信容量和提高可靠性所采用的点波束及频率复用、混合组网、切换和可变编码调制等关键技术,进行了详细剖析。分析了海事五代卫星通信系统的应用前景,并对第六代海事卫星通信系统的发展进行了展望。总结海事五代卫星的技术体制,提出了发展我国卫星移动通信系统的建议。     

地面卫星天线几何位置的计算

根据传递信息的卫星位置来确定所设地球站天线的空间坐标,这是做到收发信息的首要条件。依据卫星转发器的全向有效辐射功率和其波束能流密度的实际分布来确定地球站天线增益、发射功率范围和最大可检功率,这是设计地球站必须考虑的因素。事实上还应考     

低空空域通用航空飞机机载导航监视终端设计

针对通用航空飞机低空雷达监视存在盲区及广播自动相关监视( ADS-B )设备成本高的问题,提出以“北斗”卫星导航系统和移动公共网络通信相结合的低空空域通用航空飞机导航监视系统。系统利用“北斗”/GPS双模导航接收机获取载体位置等信息,通过移动公共网络通信系统和“北斗”卫星导航系统相互补充的通信机制可靠地将机载信息发送至地面指挥中心,并能够接收地面指挥中心的指令。考虑到“北斗”卫星导航系统通信资源的问题,系统设计了在移动公共网络通信处于盲区时导航位置等信息存储功能。系统具有成本低、与其他机载设备无电气交联等特点。相关成果对我国在低空空域通用航空飞机导航监视终端的研究具有一定的参考价值。     

卫星网络管理系统控制信道设计

设计了一套用于卫星网络管理系统的控制信道。采用TDM/TDMA专用控制信道和复接控制信道互为备份的方式保证信息传输的畅通,2种信道都可保证卫星网管所有功能的完成。主用TDM/TDMA专用控制信道,一旦专用信道中断,采用复接控制信道。复接控制信道与业务复接在一起利用业务信道传输网管信息。TDM/TDMA专用控制信道由链路适配器和突发卫星调制解调器组成,重点描述其设计方案。     

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