基于SNR比较的认知无线电协作频谱检测

协作频谱检测是认知无线电中的一项关键技术,其检测性能取决于感知节点的本地频谱检测结果的可靠性,而目前已有的方案中对此却很少考虑.对此,认为不同的认知节点信噪比(SNR)导致了各节点本地检测结果的可靠性不同,故在此基础上提出了一种基于融合中心进行SNR比较的认知无线电协作频谱检测算法.在该算法中各认知节点将本地的判决结果和估计的SNR同时发送到融合中心,然后在融合中心对SNR进行比较,按照文中设计的规则来选取有较好SNR的认知节点参与判决融合.数值分析和计算机仿真表明,该方法能有效提高检测概率,并减少参与判决融合的节点数量.     

认知无线电网络中基于最大似然准则的协同频谱检测算法研究

提出一种集中式频谱协同检测算法。各认知节点采用能量检测算法,然后使用最大似然准则进行本地判决,且把似然比作为本地判决可靠性的度量;中心节点基于可信度对接收到的认知节点本地检测数据进行数据融合。仿真结果显示,文中提出的认知节点协同频谱检测方案能够减少误检概率。特别是当信道处于深衰落时,少量节点参与协同就能获得较好的检测性能。     

一种信任度模糊分配的合作频谱感知算法

由于无线信道的多径衰落和阴影效应等因素,单个认知用户无法区分频段空闲还是授权用户的信号处于深度衰落中。合作频谱感知运用信息融合技术,通过融合多个认知用户的结果来提高频谱感知的性能。证据理论作为一种有效的不确定性推理方法,在合作频谱感知中已有较好的应用。本文将模糊集与证据理论相结合,提出一种信任度模糊分配的合作频谱感知的算法。各个认知用户首先进行本地能量检测,然后使用正态形隶属函数进行基本概率赋值,根据认知用户的检测结果分配信任度。融合中心接收所有认知用户的证据,按照Dempster组合规则进行融合,最后进行判决。仿真结果表明,信任度模糊分配的合作频谱感知算法在感知性能上或者在算法复杂度上要优于现有的证据理论合作频谱感知算法。      

基于频谱感知结果的认知无线电用户分簇方法

认知无线电用户的分簇由于不同位置频谱环境的巨大差异而成为亟待解决的问题之一。该文分析了认知无线电用户频谱感知结果之间相关性,基于分析结论提出一种基于频谱感知结果相关性的分簇算法,并考察了频谱感知结果量化对该算法的性能影响,得出增加频段数量的方式能够部分补偿量化带来的性能损失的结论。仿真显示,该文的分簇算法能够有效地对认知无线电用户进行分簇,在频谱感知结果量化的条件下,也能达到较好的分簇性能。从可靠性、准确性和自适应能力等方面,相较传统基于地理位置的分簇方法,该文所提出的分簇算法能综合考虑频谱环境的特点,更加具实用价值。     

改进双门限能量检测分簇协作频谱感知算法

针对传统频谱感知算法在低信噪比环境下检测概率较低的问题,提出改进双门限能量检测分簇协作频谱感知算法。算法将感知节点分簇,簇间信息采用OR准则硬融合,簇内双门限外节点发送1 bit判决结果进行硬融合,双门限内节点发送能量值和信噪比值进行加权软融合。加权软融合阶段构造检测概率与节点权重系数函数,利用压缩因子粒子群算法选择权重系数进行函数寻优,以最大化检测概率。仿真结果表明,在低信噪比和不同感知用户数目环境下,算法仍具有较高的检测概率。     

认知无线电中基于自相关矩阵的协作盲感知

为了克服传统的认知无线电频谱感知算法存在的不足,提出了一种基于自相关矩阵的协作式盲频谱感知方法,以提高频谱感知能力.该方法从样本自相关矩阵中提取检测统计量,采用双门限混合判决方法得到本地检测结果.认知基站将本地检测信息分成两类,并对软判决信息实施可靠性融合,最后给出全局判决结果.该方法是一种盲感知方法,不需要知道主用户...     

利用自相关矩阵的量化合作频谱感知方法

为了改善认知无线电的频谱感知性能,提出一种基于自相关矩阵的量化合作频谱感知方法,对各认知用户的本地检测结果采用多个判决门限进行有限位的量化,在融合中心采用加权投票准则对该量化信息综合处理,得出最终判决.该方法是一种盲感知方法,不需要知道主用户信号的先验知识和噪声方差信息.具体讨论了一种2 bit量化合作频谱感知方案,并将其与传统的基于能量检测的合作频谱感知方案作比较.理论分析和仿真结果表明,该方案可以有效提高频谱感知能力.     

基于信任度与信噪比的认知无线电协同频谱检测

无线网络中存在信噪比较高的恶意认知用户的情况,为了有效利用可靠的认知无线电(CR)技术用户的本地感知结果,提出了一种基于信任度的信噪比比较协同频谱感知算法,可有效剔除认知网络中存在的信噪比较高的恶意认知用户。仿真实验表明,在存在恶意认知用户的认知无线电网络中,该算法检测性能优于传统的或准则(OR)数据融合的协同频谱感知算法以及基于信噪比比较协同频谱感知算法。     

基于SNR比较的协作频谱感知研究

频谱感知是认知无线电中通过发现可用频率资源提高频谱利用率的关键技术。协作频谱感知能一定程度上消除多径和阴影的影响,为了进一步提高频谱检测性能,提出了一种基于SNR比较的协作频谱感知算法。在此算法中,各个认知用户将各自的本地判决结果和自身的SNR值发送到数据融合中心,通过SNR比较,对各CR用户进行筛选,选出符合算法要求的CR用户参加协作检测,进行数据融合。计算机仿真表明,该算法能有效提高检测性能,并减少判决融合的节点数量。     

基于Dempster-Shafer证据理论的协同频谱感知算法

认知无线电的首要任务是频谱感知,单个认知用户的频谱感知结果容易受到衰落和多径的影响,本文结合证据理论研究了多个认知用户的协同频谱感知问题.为了在融合中心未知先验信息的条件下实现对授权用户的有效检测,文章基于Dempster-Shafer证据理论,对认知用户的本地感知结果提取证据,然后在融合中心进行融合并判决,提出了一种基于Dempster-Shafer证据理论的协同频谱感知算法.仿真结果表明,该算法能够在融合中心未知先验信息情况下,获得较好的频谱感知性能.     

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.     

Technology innovation and process integrations for sub-100nm gate patterning

This paper presents a brief overview of the Applied Centura(R)DPS(R)system,configured with silicon etch DPS Ⅱ chamber, with emphasis on discussing tuning capability for CD uniformity control. It also presents the studies of etch process chemistry and film integration impact for an overall successful gate patterning development. Discussions will focus on resolutions to key issues, such as CD uniformity, line-edge roughness, and multilayer film etching integration.     

White organic light-emitting devices based on fac tris（2- phenylpyridine） iridium sensitized 5,6,11,12-tetraphenylnap -hthacene

We have fabricated the white organic light-emitting devices （WOLEDs） based on 4,4＇ -bis（2,2 -diphenyl vinyl）-1,1＇ - biphenyl （DPVBi） and phosphorescence sensitized 5,6,11,12,-tetraphenylnaphthacene （rubrene）. The device structure is ITO/2T-NATA （20 nm）/NPBX （20 nm）/CBP： x%Ir（ppy）3：0.5% rubrene （8 nm）/NPBX （5 nm）/DPVBi （30 nm）/Alq（30 nm）/LiF（0.5 nm）/A1. In the devices, DPVBi acts as a blue light-emitting layer, the rubrene is sensitized by a phosphorescent material, fac tris （2-phenylpyridine） iridium [Ir（ppy）3], acts as a yellow light-emitting layer, and N,N＇ -bis- （1-naphthyl）- N,N＇ -diphenyl -1, 1＇ -biphenyl-4,4＇ -diamine （NPBX） acts as a hole transporting and exciton blocker layer, respectively. When the concentration of Ir （PPY）3 is 6wt%, the maximum luminance is 24960 cd/m^2 at an applied voltage of 15 V, and the maximum luminous efficiency is 5.17 cd/A at an applied voltage of 8 V.     

Complete approach to automatic identification and subpixel center location for ellipse feature

To meet the need of automatic image features extraction with high precision in visual inspection, a complete approach to automatic identification and sub-pixel center location for similar-ellipse feature is proposed. In the method, the feature area is identified automatically based on the edge attribute, and the sub-pixel center location is accomplished with the leastsquare algorithm. It shows that the method is valid, practical, and has high precision by experiment. Meanwhile this method can meet the need of instrumentation of visual inspection because of easy realization and without man-machine interaction.     

小角度扩展相关性近似算法分析

本论文提出一种在多天线MIMO信道相关性建模中小角度扩展近似理论算法,并应用于分析MIMO系统性能。分析中分别对三种不同角能量分布情况下的空间相关性研发快速近似计算法,并同时提出双模(Bi-Modal)角能量分布情况下的近似运算。通过分析这些新方法的近似效率,可以得到计算简单、复杂度低、而且符合实际的MIMO相关信道矩阵,对系统级的快速高效计算法的研究和系统级的评估以及误差分析具有重要的意义。     

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.