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题名LT码的远程光纤通信系统性能研究
被引量：1
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作者
邵鸿翔
高宏峰
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机构
河南科技大学电子信息工程学院
洛阳理工学院工程训练中心
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出处
《安徽大学学报（自然科学版）》
CAS
北大核心
2014年第2期68-73,共6页
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基金
国家自然科学基金资助项目(61101167)
国家航空科学基金资助项目(20110142002)
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文摘
针对传统前向纠错码在光纤通信系统中不能根据信道状况自动调整码率和常用光纤信道模型不准确的问题,提出基于码率可调LT码的非对称卡方噪声分布的光纤通信系统.在此基础上,针对LT码编码度1断层和生成矩阵中短环影响译码的问题,设计基于指数健壮度分布的去4环的联合编码算法.仿真结果表明,该文算法相比鲁棒孤波度分布译码算法效果有所提高,在收包数量一定的前提下,提高了译码成功率;同时LT码在卡方信道模型下的编译码性能优于其他信道.
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关键词
LT码
编码度分布
去4环
BP译码
卡方光纤信道模型
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Keywords
LT code
degree distribution
avoid 4-loop
belief propagation coding
chi-square channel model
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分类号
TN913.7
[电子电信—通信与信息系统]
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题名表面等离子体无掩膜干涉光刻系统的数值分析(英文)
被引量：5
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作者
董启明
郭小伟
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机构
电子科技大学光电信息学院
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出处
《光子学报》
EI
CAS
CSCD
北大核心
2012年第5期558-564,共7页
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基金
The National Natural Science Foundation of China(No.60906052)
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文摘
表面等离子体激元具有近场增强效应,可以代替光子作为曝光源形成纳米级特征尺寸的图像.本文数值分析了棱镜辅助表面等离子体干涉系统的参量空间,并给出了计算原理和方法.结果表明,适当地选择高折射率棱镜、低银层厚度、入射波长和光刻胶折射率,可以获得高曝光度、高对比度的干涉图像.入射波长为431nm时,选择40nm厚的银层,曝光深度可达200nm,条纹周期为110nm.数值分析结果为实验的安排提供了理论支持.
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关键词
干涉光刻
表面等离子体激元
克莱舒曼结构
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Keywords
Interference lithography
Surface plasmon plortiton
Kretschmann structureCLCN: TN305.7 Document Code:A Article ID:1004-4213(2012)05-0558-70 IntroductionThere is a growing interest in exploring new nanolithography techniques with high efficiency,low cost and large-area fabrication to fabricate nanoscale devices for nanotechnology applications.Conventional photolithography has remained a useful microfabrication technology because of its ease of repetition and suitability for large-area fabrication[1].The diffraction limit,however,restricts the fabrication scale of photolithography[2].Potential solutions that have actually been pursued require increasingly shorter illumination wavelengths for replicating smaller structures.It is becoming more difficult and complicated to use the short optical wavelengths to reach the desired feature sizes.Other methods such as electron beam lithography[3],ion beam lithography[4],scanning probe lithography[5],nanoimprint lithography(NIL)[6],and evanescent near-field optical lithography(ENFOL)[7] have been developed in order to achieve nanometer-scale features.As we know,the former three techniques need scanning and accordingly are highly inefficient.In NIL,the leveling of the imprint template and the substrate during the printing process,which determines the uniformity of the imprint result,is a challenging issue of this method.ENFOL have the potential to produce subwavelength structures with high efficiency,but it encounters the fact that the evanescent field decays rapidly through the aperture,thus attenuating the transmission intensity at the exit plane and limiting the exposure distance to the scale of a few tens of nanometers from the mask.In recent years,the use of surface-plasmon polaritons(SPPs) instead of photons as an exposure source was rapidly developed to fabricate nanoscale structures.SPPs are characterized by its near field enhancement so that SPP-based lithography can greatly extend exposure depth and improve pattern contrast.Grating-assisted SPP interference,such as SPP resonant interference nanolithography[8] and SPP-assisted interference nanolithography[9],achieved a sub-100nm interference pattern.The techniques,however,are necessary to fabricate a metal grating with a very fine period and only suitable for small-area interference.To avoid the fabrication of the metal grating,a prism-based SPP maskless interference lithography was proposed in 2006,which promises good lithography performance.The approach offers potential to achieve sub-65nm and even sub-32nm feature sizes.However,the structure parameters are always not ideal in a real system.One wants to know how much influence the parameter variations have on the pattern resolution and what variations of the parameters are allowed to obtain an effective interference.Thus,it is necessary to explore the parameter spaces.1 SPP maskless interference lithography systemThe SPP maskless interference lithography system is shown in Fig.1.A p-polarized laser is divided into two beams by a grating splitter,and then goes into the prism-based multilayer system.Under a given condition,the metal film can exhibit collective electron oscillations known as SPPs which are charge density waves that are characterized by intense electromagnetic fields confined to the metallic surface.If the metal layer Fig.1 Schematic for SPP maskless interference lithography systemis sufficiently thin,plasma waves at both metal interfaces are coupled,resulting in symmetric and antisymmetric SPPs.When the thickness h of metal film,dielectric constant ε1,ε2,ε3 of medium above,inside,below the metal film are specified,the coupling equation is shown as followstanh(S2h)(ε1ε3S22+ε22S1S3)+(ε1ε2S2S3+ε2ε3S1S2)=0
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分类号
TN305.7
[电子电信—物理电子学]
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