基于IRS辅助的MIMO车联网系统联合波束成形设计

针对MIMO车联网系统中V2I和V2V共享频谱的情形,提出了一种IRS辅助的联合波束成形设计方法。在保证V2V用户数据速率需求、V2I基站发射功率受限和IRS反射相移模约束等条件下,以最大化V2I用户的信道容量为目标,联合优化基站端发送预编码和IRS端的反射相移矩阵。采用最小均方误差规则、矩阵分析理论和内逼算法把非凸且变量耦合的优化问题转换为解耦后的凸优化问题,并提出一种交替迭代优化算法获得原问题的解。对所提算法的性能进行仿真,分析了IRS反射单元数、IRS部署位置和车速对车联网频谱效率的影响。仿真结果表明,所提算法收敛性较好,若在基站附近部署IRS,利用所提的联合波束成形方法能最大限度地提高车联网频谱效率。     

分布式IRS辅助毫米波MU-MISO系统联合波束成形设计

为解决非视距场景下毫米波多用户多输入单输出(MU-MISO)系统下行链路的可靠性通信问题,提出一种分布式智能反射表面(IRS)辅助多用户通信的联合波束成形设计方案.考虑功率和恒模约束,以用户加权和速率最大为目标,将基站有源波束成形和多个IRS无源波束成形联合建模为非凸优化问题.利用闭式分式规划技术解耦该联合优化问题为易...     

IRS辅助毫米波MIMO系统波束赋形优化的低复杂度方案

智能反射表面（intelligent reflective surface,IRS）被认为是无线通信网络的前景技术之一。然而由于IRS无源波束赋形优化受到本身所具有的非凸恒模约束,现有工作在IRS辅助的多输入多输出（multiple input multiple output,MIMO）系统中的研究只能得到次优解且具有较高的复杂度。本文考虑一个单用户IRS辅助通信的毫米波MIMO系统,为了最大化频谱效率,优化通信接入点AP（access point）端有源和IRS端无源波束赋形矩阵。首先将有源和无源波束赋形矩阵解耦,得到AP的最优有源波束赋形解,将IRS无源波束赋形设计问题推导为一个非凸二次约束二次规划（quadratically constrained quadratic programming,QCQP）问题;采用低复杂度的连续闭式解（successive closed form,SCF）算法求解IRS无源波束赋形矩阵,为了衡量SCF算法性能,分析对比了现有的最优分支界定（branch and bound,BnB）算法。仿真结果验证了SCF算法在IRS相移连续和离散时均能在较低复杂度达到较高的频谱效率性能。      

IRS和人工噪声辅助的MIMO-SWIPT系统安全传输方案设计

针对多天线无线携能通信系统中能量收集节点作为潜在窃听者的信息安全问题，提出了一种智能反射面(Intelligent Reflecting Surface, IRS)和人工噪声辅助的物理层安全传输方案。首先考虑发射功率、能量收集门限以及IRS单位模约束，以最大化系统安全速率为优化目标，在合法用户直射链路不可用的情况下，联合设计发射端波束赋形矩阵、人工噪声协方差矩阵以及IRS相移矩阵，建模一非线性多变量耦合的非凸优化问题；接着利用均方误差准则等价转换非凸目标函数，并利用连续凸逼近方法(Successive Convex Approximation, SCA)处理非凸的能量收集约束；最后基于交替优化框架，分别用拉格朗日对偶方法和基于价格机制的优化最小化(Majorization-Minimization, MM)算法求解发射端变量和IRS端变量。仿真结果表明，与现有方案相比，所提算法能够在保障能量收集需求的同时大幅度提升系统的安全性能。     

基于不完美硬件系统的双智能反射面辅助波束赋形设计

在发射端具有不完美硬件的多输入多输出（Multiple Input Multiple Output,MIMO）系统中，存在失真噪声和干扰噪声，这导致用户侧接收信号受损，系统频谱效率低下。为解决此问题，考虑使用双智能反射面（Intelligent Reflecting Surface,IRS）辅助，联合优化基站波束赋形矩阵和两个IRS的反射相移矩阵，最大化多用户和速率。目标函数是变量高度耦合、复杂的非凸优化问题，分别使用交替优化方法、半正定松弛（Semi-Definite Relaxation,SDR）算法和奇异值分解归一化的方法求解。仿真结果表明，在发射端具有不完美硬件的MIMO系统中，与单IRS辅助和无IRS方案相比，使用双IRS辅助通信能够获得更好的系统频谱效率。     

智能反射面实现空间调制的安全系统性能分析

为了解决安全空间调制系统中合法信道增益差的问题,提出了一种用智能反射面(Intelligent Reflective Surface,IRS)实现空间调制的物理层安全传输方案。IRS接收到发射端发射的幅相调制信号后,通过选择不同的IRS反射元件序号对空域部分信息进行映射,再将信号反射到接收端,以增大窃听端获取完整信息的难度。此外,在发射端采用波束赋形和天线分集技术,提高了系统有效性和可靠性。对系统的保密速率和误比特率进行的理论分析和仿真实验结果表明,所提方案不仅可以提高系统保密速率,还可以降低合法接收端的误比特率。     

智能反射面辅助多用户大规模MIMO系统的联合波束成形

智能反射面（Intelligent Reflecting Surface,IRS）作为面向第6代通信的关键技术之一具有创新、高效、节能和成本效益高等特点,但其联合波束成形设计为非凸优化问题,仍然是具有挑战的难题。为此,提出了一种用于IRS辅助多用户大规模多输入多输出系统的联合波束成形设计方案,以实现系统数据速率最大化。该方案在基站端采用迫零波束成形以消除用户间干扰,同时在IRS端设计了近最优反射波束成形以实现系统和数据速率最大化。仿真结果表明,该方案可获得较高的系统和数据速率,也为IRS位置布局的选择提供了数据支持与参考准则。     

基于智能反射面辅助的无线供电通信网络鲁棒能效最大化算法

为了解决能量收集效率易受到障碍物阻挡和信道不确定性影响的问题,该文提出一种基于智能反射面(IRS)辅助的无线供电通信网络鲁棒能效(EE)最大化算法。首先,考虑最小收集能量、IRS相移、最小吞吐量等约束,基于有界信道不确定性,建立一个联合优化能量波束、相移、传输时间的多变量耦合非线性资源分配模型。然后,利用最坏准则、变量替换和S-Procedure等方法,将原非凸问题转换为确定性凸优化问题,同时,提出一种基于迭代的鲁棒能效最大化算法进行求解。仿真结果表明,与现有算法比较,该文算法具有较好的能效和鲁棒性。     

基于IRS辅助的SWIPT物联网系统安全波束成形设计

为满足绿色万物互联的智能信号处理部署和物理层安全的新要求,针对基于智能反射面辅助的无线携能通信物联网系统中可持续能量供应紧缺问题,提出了一种安全波束成形设计方法。考虑保密速率、发射功率和IRS反射相移约束,以最大化能量采集器采集功率为目标,联合优化基站发射波束成形矩阵和干扰机协方差矩阵以及IRS相移,将优化问题建模为具有二次型约束的非凸二次型规划问题。利用松弛变量、半定松弛法、辅助变量和序列参数凸逼近法将非凸的二次型问题转化为等价的凸问题,并提出一种交替迭代优化算法获取原问题的可行解。仿真结果表明,所提算法能够快速收敛,且与基准方案相比能有效地提升性能。     

基于智能反射面辅助的无人机中继系统安全通信方法

为了提高无人机中继系统的安全通信性能,解决无线信道受障碍物遮挡问题,该文提出一种基于智能反射面(IRS)辅助的无人机(UAV)中继系统安全通信方法。在所提方法中,通过联合优化UAV的位置、基站波束成形和IRS相移,最大化系统的最小保密速率。为了解决这个复杂的非凸优化问题,该文将原问题分解为UAV位置优化子问题、波束成形和IRS相移优化两个子问题。使用1阶泰勒展开处理优化问题中的非凸项,然后提出一种交替优化的算法进行求解。仿真结果表明该文提出的算法能提高系统的最小保密速率,并且具有良好的收敛性。     

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.     

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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