无线传感器网络中节点合作定位研究和仿真

采用最大似然估计(MLE)方法和共轭梯度(CG)算法,通过软件模拟无线传感网络的节点合作定位算法,仿真验证了基于接收信号强度RSS和到达时间TOA测距两种定位方法的有效性,并且研究了盲节点数对网络估计克拉美-罗界(CRB)的影响.仿真结果表明基于以上两种测距方法的节点定位估计方差满足网络估计界CRB,并且随着系统盲节点数的增加,网络估计界CRB会减小,即节点位置的估计也可以更精确.     

基于惯性鞋载传感器的人员自主定位粒子滤波方法

为了解决卫星导航信号被遮挡条件下定位问题,该文提出一种基于惯性鞋载传感器的高精度人员自主定位方法。该方法通过经典的拓展卡尔曼滤波辅助的零速更新(ZUPT-aided EKF)算法解算鞋尖惯性测量数据得到人员的初步运动轨迹,并创新性地提出一种粒子滤波框架下利用建筑物结构先验知识对轨迹进行修正的方法。根据大多数建筑物的结构,将行走平面划分为8个方向,包含4个主方向(走廊朝向)和4个辅助方向。根据粒子偏离8方向的程度按照高斯函数对粒子的权值进行更新,并用剩余重采样的方法避免了粒子的退化。实测数据验证了该文提出的方法,结果表明:该方法比轨迹修正前和传统轨迹修正的方法有更好的精度,在861 m的复杂轨迹下定位误差仅为2.7 m,定位精度优于0.5%;同时该方法有较好的一致性,不同楼层间的行走定位误差保持在2 m内, 可以进行稳定持续地定位。     

一种基于相位轨迹的OFDM信号盲分析方法

随着第五代移动通信技术、低轨卫星互联网等通信系统的发展，正交频分复用(Orthogonal Frequency Division Multiplexing, OFDM)技术凭借良好的频谱效率得到日益广泛的应用。但OFDM系统信号参数复杂，对非合作条件下的盲信号分析带来了较大困难，需要在尽可能少的先验信息下，判定信号参数。为此，提出了一种基于相位轨迹特征的OFDM信号盲分析方法，利用OFDM信号固有的循环周期性，粗估计子载波数及子载波间隔，在此基础上通过非线性变换等处理获取子载波间及符号间的相位变化轨迹，基于相位变化轨迹分析其反映的采样定时误差、载波频率偏差等参数信息并修正估计值，最终通过信号接收误码率进行估计参数正确性验证，实现了对OFDM信号盲分析。仿真分析结果表明，在信噪比(SNR)大于8 dB时，即可实现参数准确估计，优于利用先验信息的相关处理方法。     

基于多级维纳滤波的盲信噪比估计

提出了一种基于多级维纳滤波(MSWF: Multistage Wiener Filter)的盲信噪比估计算法。结合信号子空间分解理论,该方法利用多级维纳滤波器的相关相减结构(CSA: Correlation Subtraction Algorithm)前向递推实现含噪信号空间分解,避免了传统方法对信号自相关矩阵进行复杂的特征值分解运算,并以此估计信号功率和噪声功率来完成盲信噪比估计。在加性高斯白噪声(AWGN)信道条件下进行信噪比估计仿真,仿真表明,当实际信噪比在-7~25dB范围内时,估计器的估计标准偏差小于0.5dB,且性能优于常规方法。设定实际信噪比为10dB,当接收码元数目为100时,对所有仿真的调制方式信噪比估计标准偏差小于0.35dB,证明了估计器在小样本支撑环境下实现信噪比快速盲估计的能力。      

基于多天线接收机的信号调制方式识别

针对存在未知载波频偏(CFO)的线性调制分类,提出一种混合似似然比检测(qHLRT)分类器.并且通过使用多天线接收机来进一步增强分类性能.一种基于盲源分离技术的CFO估计器用于qHLRT分类器中,同时对不同天线支路的相移作出估计.针对AWGN信道M进制QAM信号进行仿真,结果显示带有该估计器的qHLRT分类器可以有效降低未知CFO的影响,利用空间分集可以进一步提高分类器性能.     

基于无线传感器网络与无迹卡尔曼滤波的室内定位系统设计

基于接收信号强度指示(Received Signal Strength Indicator, RSSI)的测距方法和无迹卡尔曼滤波(Unscented Kalman Filter, UKF)实现了一种无线传感器网络室内定位系统。系统主要由协调器节点、锚节点和盲节点组成，首先由盲节点发送RSSI信标信号至锚节点处，锚节点接收信标信号后做均值处理，并将自身位置信息一起打包回发给盲节点；然后盲节点将定位信息的相关数据通过协调器无线发送至上位机；最后在上位机中完成对盲节点的定位计算。为进一步提高定位精度，首先应用三边定位方法获得盲节点的初步定位结果，然后采用无迹卡尔曼滤波实现了二次精确定位。使用C#语言开发上位机软件，在20 m×20 m的定位范围内，对10个随机位置处的盲节点进行了定位测试，其中最大定位误差为1.52 m,最小误差为0.50 m,平均定位误差为1.04 m。结果表明所提出的定位算法性能良好，系统定位方案切实有效。     

基于Lembda网络和LSTM的车辆轨迹预测

驾驶员在驾驶时,会对周围车辆的轨迹进行预测,并且采取一个安全的行为模式,从而减少道路事故的发生.出于这个想法,研究人员基于深度学习的模型,对车辆的轨迹进行预测,从而提升自动驾驶车辆的安全性.通过不断分析获得的驾驶数据,深度学习可以得到其它汽车的行为模式并进行预测.相较于过去的方案,基于深度学习方案在轨迹预测上具有优势,本文基于transformer模型的LSTM(长短期记忆网络)编码隐藏参数,反映周围车辆的驾驶意图,再通过Lembda层获得这些车辆对预测车辆的影响,最后通过LSTM解码获得预测的轨迹.相较于以往的方案,应用Lembda层的方案计算速度更快,同时实验表明相较于以往方案轨迹预测精度有提升.     

信噪比盲估计算法性能比较

为了实现非协作环境下的通信信号信噪比估计,本文在功率谱分析的基础上,提出了一种基于功率谱差分的信噪比盲估计算法,并将其与传统的基于奇异值分解的信噪比盲估计算法进行了比较。理论与仿真结果表明,与传统方法相比,本文提出的算法不但复杂度低,而且在低信噪比情形下仍具有较高的估计精确度和稳健性。     

基于Wi-Fi即时定位与映射像素模板匹配的室内运动地图构建与定位

传统指纹定位方法由于建库人力时间开销大、系统通用性不强约束着指纹定位系统的推广,为了解决该问题同时结合即时定位与映射(SLAM)技术的优势,该文提出一种新的Wi-Fi/微机电系统(MEMS)融合室内运动地图构建与定位方法。首先利用行人航迹推算(PDR)、最小描述长度(MDL)原则和基于密度的空间聚类算法(DBSCAN)对众包运动轨迹进行预处理,提出基于轨迹主路径的运动地图构建方法。之后提出基于像素模板的地图匹配方法获取地图的绝对位置,并采用抗差扩展卡尔曼滤波(EKF)对目标位置进行最优估计。实验结果表明,所提聚类方法可以准确构建各区域运动地图,在少量的人力时间开销下实现较高的定位精度。     

一种基于单目视觉的无人机室内定位方法

目前,无人机定位技术主要依赖以GPS(Global Positioning System)为代表的全球定位系统,然而在室内等GPS信号缺失的地方进行定位则比较困难。另外,传统的室内定位技术主要采用蓝牙、WiFi、基站定位等多种方式融合成一套定位体系,但是该类方法受环境的影响比较大,而且往往需要部署多个设备。此外,这种方式只能得到远近信息,无法知道设备在空间中的姿态。该文提出一种基于单目视觉的无人机室内定位方法。首先,通过无人机机载相机拍摄的图像,结合特征点法和直接法,先跟踪特征点,然后利用直接法根据关键点进行块匹配,估计相机位姿。然后利用深度滤波器对特征点进行深度估计,建立一个当前环境的稀疏地图,最后利用ROS (Robot Operating System)的3维可视化工具RVIZ对真实环境进行仿真。仿真结果表明,所提方法在室内环境下可以获得良好的性能,定位精度达到0.04 m。     

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