BBO晶体厚度对光谱相位干涉仪性能的影响

基于光谱相位相干直接电场重建法(SPIDER)测量飞秒激光脉冲的原理,建立了BBO晶体光谱滤波作用的计算模型,数值模拟了不同参数BBO晶体的视频效率带宽,给出了对于不同宽度的待测脉冲及应选取的：BBO晶体的厚度范围,并在实验中给予验证。结果表明：对于20fs的脉冲,可采用厚度为50μm的BBO晶体;而对于50fs的脉冲,采用100μm厚的BBO晶体就已经能够满足其谱宽的要求。     

用改进的光谱相位相干直接电场重构法装置测量飞秒激光脉冲的相位

在对光谱相位相干直接电场重构法(SPIDER)硬件和软件进行深入研究的基础上,建立了光谱相位相干直接电场重构法测量系统。测量装置中,利用厚度为50μm的非线性晶体(BBO)来保证测量装置的带宽,并对分束镜进行改进,使之引入色散减小。自行开发了一套基于Labveiw软件的光谱相位相干直接电场重构法测量系统,并能够用于实时测量。其中在还原算法中以脉冲对倍频干涉条纹中的ωτ作为线性快变项,并只对具有干涉条纹部分的频率范围进行还原相位,大大提高了光谱相位相干直接电场重构法测量的精度。用此系统测量了钛宝石激光振荡器的输出脉冲特性,并与干涉自相关比较,证实了测量的准确性。     

脉冲相位共轭光研究的进展

近年来,随着超短脉冲激光技术的迅速发展,脉冲相位共轭技术,尤其是fs脉冲相位共轭技术,愈来愈受到重视。本文综述了脉冲相位共轭,包括ns,ps和fs相位共轭研究的进展。     

基于SPIDER法测量飞秒脉冲的数值计算与模拟

为了测量飞秒脉冲的振幅和相位,采用光谱相位相干电场重构法(SPIDER)的光谱图数值分析公式,对高斯强度分布的线性啁啾脉冲、立方相位啁啾脉冲进行数值计算与数值模拟,并重构出飞秒脉冲的光谱相位,其模拟的结果与理论符合较好,光谱相位相干电场重构法能完全测量飞秒脉冲的振幅和相位.     

光谱相位相干技术测量飞秒脉冲的倍频误差

从理论上推导了第Ⅱ类相位匹配下宽带飞秒脉冲的二次谐波光场,分析输入飞秒脉冲的非共线相位匹配方式、脉冲带宽引起相位失配与群速失配对测量的影响。结果表明,为了消除飞秒脉冲的带宽影响,需要对测量记录的光强乘以一个调制因子;测量相位误差与非共线相位匹配的夹角和晶体长度成正比;相位失配与群速失配产生相位测量误差,且第Ⅱ类相位匹配方式下脉冲附加相位值较大;强度和相位误差需要在脉冲重建结果中补偿。     

光谱相位相干电场重建法的准确相位还原

基于光谱相位相干直接电场重建法(SPIDER)原理,提出采用小波变换和傅里叶变换两种算法互校的方式,确定小波变换法的形状因子和傅里叶变换法的滤波窗口宽度,当两种算法的还原结果一致时,就实现了SPIDER的准确相位还原.通过自制的SPIDER测量仪和自编的SPIDER相位还原软件,实现了对复杂相位的准确还原.     

CATV光传输中相位调制抑制相位干涉噪声的理论分析

对附加相位调制抑制相位干涉噪声的方法进行了理论分析与计算,结果表明：在光纤AM－CATV外调制传输系统中,对传输光载波信号引入附加相位调制,当相位调制信号的频率为CATV频带的2倍以上时,可以有效地抑制相位干涉噪声的发生,相位调制度越大,抑制效果越好。     

十三步光栅横向剪切干涉相位复原算法

光栅横向剪切干涉仪能够实现超高精度检测光学系统的波像差,是当前光刻镜头研发的重要组成内容之一。零级串扰和相移误差是影响光栅剪切干涉仪检测精度的两个主要因素,为此,提出了一种十三步光栅剪切干涉相位复原算法,在消除零级串扰的同时,还能够极大地降低对相移误差的苛刻要求。分析表明,当相移误差不大于25°时,相位复原误差小于0.01°(即2.8×10-5λ)。对于λ=193.386nm,相位复原误差小于0.005nm。因此,通过系统误差校正,光栅剪切干涉仪检测光刻镜头系统波像差的精度能够达到亚纳米级。     

超短脉冲激光相干层析成像技术的理论分析与实验

基于光学弱相干反射测量而发展出来的光学相干层析(Optical Coherence Tomography,简称OCT)技术是一种新型成像技术,由于它在生物医学领域的诊断或疗效监测等方面巨大的应用潜力, 近年来发展极为迅速.与其它医学中常用的光学、光谱测量方法及诸多成像方法相比, OCT由于其高时空分辨和在体测量的特点, 将成为继X射线CT、核磁共振成像(MRI)之后, 又一新的重要诊断手段.将超短脉冲飞秒激光器作为光源的光纤化光学相干层析技术, 利用光源光强高、单脉冲能量低的特点, 有利于避免测量对活体组织的损伤,同时又能快速成像, 获得高空间分辨和大的探测深度.考虑材料色散对光脉冲信号的展宽,由于色散,当脉冲通过一定长度的光纤时, 脉冲将在时域上变宽.显然, 如果有大量的脉冲在光纤的入射孔径处,当光脉冲到达光纤的输出端时,脉冲会变宽,也许会重叠起来而影响光的相干性.本文通过严格的数学推导,得到了系统的相干长度公式表达式,此式与连续光源得到的相干长度公式是一样的;另外,脉冲通过一定长度的光纤时, 时间脉冲将变宽,但光脉冲的频谱分布并未发生改变,脉冲时域上的展宽不影响光源的相干长度.在此基础上,利用我们研制的半导体泵浦超快飞秒掺钛蓝宝石激光器光源的OCT光纤实验系统,对动物组织样品进行了层析成像,得到了样品表层的OCT层析结构图像.(OC4)     

光谱相位相干直接电场重构法测量飞秒脉冲的适用性问题

分析了现有光谱相位相干直接电场重构法(SPIDER)系统的一个缺点,即需预先估计待测脉冲的特性,来设定合适的系统参数.因而其适用范围受到一定限制,特别是在测量啁啾脉冲时容易出现偏差.实验用SPIDER系统分别测量了钛宝石飞秒激光器输出的脉冲及其经BK7玻璃块展宽得到的啁啾脉冲,测得啁啾脉冲的宽度为295 fs,作剪切量修正后测得脉宽为322 fs,后者更接近理论预期的313 fs.这表明SPIDER系统测量啁啾脉冲时,如果色散器提供的色散量不够大,会出现一定程度的偏差.通过补充记录两个和频脉冲的光谱,修正实际的剪切量,可有效减小误差,但问题仍未完全解决.     

飞秒激光光谱位相干涉仪的数值模拟与分析

对用光谱位相相干直接电场重建法 (SPIDER)测量飞秒光脉冲啁啾特性的光谱位相干涉仪进行了数值模拟 ;对假设具有不同类型啁啾的飞秒脉冲进行光谱位相重构 ,还原出时域脉冲强度包络和位相 ,并与实验结果进行了比较     

平视显示器视差自动测量系统的设计与实现

针对平视显示器现场调试过程中视差检测存在主观性大、不易给出定量结果的问题,研制了一套用于平视显示器视差自动检测装置.本装置采用传统光学系统,利用CCD光电耦合器件将大视场平行光管分划像清晰成像,放入被测平显,再次将分划成像,并对此图像进行处理.通过自制计算软件,计算给出视差调节量,从而进行自动检测.利用这一装置与未采用...     

广播电视发射传输机房管理系统的设计与实现

扬州广播电视局广播电视发射传输部的主要职责和任务是 ,做好扬州电视台两套电视节目和扬州电台两套调频广播节目以及中央电视台和省电视台节目的发射传输工作。日常工作中值班人员每天都需要记录电视、调频发射机运行状态数据 ,维护人员也经常进行机器设备的维修和测试工作 ,并记录各种故障现象和测试数据。以前 ,这些数据都采用手工填写 ,因而存在资料不易保管 ,数据不易统计 ,工作效率低 ,共享性、可重复利用性差等缺点。此外 ,由于地理位置的原因 ,广播电视发射传输部远离广电中心大楼 ,部门和广电中心领导联系工作存在不便。随着计算机…     

光纤脉冲分析仪的设计

针对光纤色散特性会引起传输信号的畸变,限制通信容量,指出对光纤色散参数、光信号在长距离传输后脉冲展宽程度的准确测量,可以提供可靠的设计数据来源,在实际的工程应用中有着重要意义.根据对色散基本理论的讨论,分析光脉冲在光纤中传播的展宽现象.自行研制了一套用于多模光纤色散测量的脉冲展宽测试设备,已应用在教学实验和工程实践中.     

Analysis and VLSI Realization of a Blind Beamforming Algorithm

We present the fixed-point analysis and VLSI realization of a maximum-power blind beamforming algorithm. This algorithm consists of the computation of a correlation matrix and its dominant eigenvector, and we propose that the latter be accomplished by the power method. After analyzing the numerical stability of the power method, we derive a division-free form of the algorithm. Based on a block-Toeplitz assumption, we design an FIR filter based system to realize both the correlation computation and the power method. Our ring processor, which is optimized to implement digital filters, is used as the core of the architecture. A special technique for dynamically switching filter inputs is shown to double the system throughput. VLSI design is discussed in detail and chip fabrication results are presented.Fan Xu received the B.S. and M.S. degrees in electronics engineering from Tsinghua University, Beijing, China, in 1993 and 1996, respectively, and the Ph.D. degree in electrical engineering from the University of California, Los Angeles, in 2001. His Ph.D. research focused on algorithm design and analysis for digital signal processors and eigenvector estimation architectures.In 1997, he held an internship at Bell Labs, Lucent Technologies, Holmdel, NJ, where he worked on equalization algorithms for cellular systems. He joined Broadcom Co., Irvine, CA, in 2001. His research interests include VLSI signal processing, customized digital signal processor, efficient hardware architectures for adaptive signal processing and high-performance VLSI design.Guichang Zhong received the B.S. degree from Xi an Jiaotong University, China, in 1996 and the M.S. degree from the Institute of Microelectronics of Chinese Academy of Sciences, Beijing, China, in 2000, both in electrical engineering. He is currently working toward the Ph.D. degree in integrated circuits and systems at the University of California, Los Angeles.His present research interests are in high-performance VLSI digital signal processors design, with an emphasis on reconfigurable and energy-efficient architecture.Alan N. Willson, Jr. received the B.E.E. degree from the Georgia Institute of Technology, Atlanta, in 1961, and the M.S. and Ph.D. degrees from Syracuse University, Syracuse, NY, in 1965 and 1967 respectively.From 1961 to 1964 he was with IBM, Poughkeepsie, NY. He was an Instructor in electrical engineering at Syracuse University from 1965 to 1967. From 1967 to 1973 he was a Member of the Technical Staff at Bell Laboratories, Murray Hill, NJ. Since 1973, he has been on the faculty of the University of California, Los Angeles (UCLA), where he is Professor of Engineering and Applied Science in the Electrical Engineering Department. In addition, he served the UCLA School of Engineering and Applied Science as Assistant Dean for Graduate Studies from 1977 through 1981 and as Associate Dean of Engineering from 1987 through 2001. He has been engaged in research concerning computer-aided circuit analysis and design, the stability of distributed circuits, properties of nonlinear networks, theory of active circuits, digital signal processing, analog circuit fault diagnosis, and integrated circuits for signal processing. He is editor of Nonlinear Networks: Theory and Analysis (New York: IEEE Press, 1974). In 1991 he founded Pentomics, Inc.Dr. Willson is a member of Eta Kappa Nu, Sigma Xi, Tau Beta Pi, the Society for Industrial and Applied Mathematics, and the American Society for Engineering Education. From 1977 to 1979, he served as Editor of the IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS. In 1980, he was General Chairman of the 14th Asilomar Conference on Circuits, Systems, and Computers. During 1984, he served as President of the IEEE Circuits and Systems Society. He was the recipient of the 1978 and 1994 Guillemin-Cauer Awards of the IEEE Circuits and Systems Society, the 1982 GeorgeWestinghouse Award of the American Society for Engineering Education, the 1982 Distinguished Faculty Award of the UCLA Engineering Alumni Association, the 1984 Myril B. Reed Best Paper Award of the Midwest Symposium on Circuits and Systems, the 1985 and 1994 W.R.G. Baker Awards of the IEEE, the 2000 Technical Achievement Award and the 2003 Mac Van Valkenburg Award of the IEEE Circuits and Systems Society.     

WCDMA下行链路接收机算法的分析及实现

本文介绍了WCDMA下行链路接收机的实现原理及过程,对其中的关键算法进行了详细的分析,根据对其性能比较,结合其复杂度综合地选取各单元使用的算法,仿真证明,所选取的下行接收算法具有优良的性能.     

电信统计分析系统优化的设计和实现

从用户资料与通话记录的关联方法和统计方法两个方面介绍统计分析系统优化的设计思想和实现，首先，把所有经过哈夫曼编码压缩的用户资料利用UNIX中共享内存的技术存储，使所有的统计进程都能共享地访问，并用折半查找法快速地对用户资料进行查找，以解决大量通话数据与大量的用户资料关联的难题。另外，通过几种统计方法的比较，阐述了用平衡的二叉排序树存放统计结果统计方法的优点，使用后可以满足多维度、多指标的统计分析要求。     

快速锁定频合器解决方案的分析与实现

跳频通信系统中频率合成器的频率转换速率直接影响到系统的抗干扰能力.文章对锁相环频率合成器的锁定时间进行了分析与仿真,介绍了各种途径频率转换快速锁定的解决方案,采用其中的基于DDS分数分频的锁相环频合器方案,实现了S波段宽带跳频频合器测试,结果表明:在频率间隔为500 MHz时,相位锁定时间为110 μs,且相噪低、频谱纯度高,可大大提升系统性能.