图像增强方法的研究与实现
在图像处理中,图像增强技术对于提高图像的质量起着重要的作用"它通过有选择地强调图像中某些信息而抑制掉另一些信息,以改善图像的视觉效果,将原图像转换成一种更适合于人眼观察和计算机进行分析处理的形式"本文着重对图像增强方法中的灰度变换!直方图均衡化!模糊增强进行了深入的研究,针对增强过程中遇到的一些问题,提出了相应的解决方法"对于分段线性变换方法中如何划分灰度区间进行变换这一关键问题,给出了基于区域分割的分段线性变换方法,加快了调整灰度区间的过程,提高了算法的执行效率"为了适应图像的局部亮度特性,给出了基于抛物线调整的直方图均衡化方法,可以调节图像的明暗程度,增强区域的对比度,同时给出了一种选
- 2020-12-02下载
- 积分：1
光纤通信中数字信号处理
论文，高速光纤通信与数字信号处理。相干光接收，频偏估计，相位估计，算法。Y175785独创性(或创新性)声明本人声明所呈交的论文是本人在导师指导下进行的研究工作及取得的研究成果。尽我所知,除了文中特别加以标注和致谢中所罗列的内容以外,论文中不包含其他人已经发表或撰写过的研究成果,也不包含为获得北京邮电大学或其他教育机构的学位或证书而使用过的材料。与我一同工作的同志对本研究所做的任何贡献均已在论文中作了明确的说明并表示了谢意。申请学位论文与套料若有不实之处,本人承担一切相关责任。本人签名:-/b日期:200列2关于论文使用授权的说明学位论文作者完全了解北京邮电大学有关保留和使用学位论文的规定,即:研究生在校攻读学位期间论文工作的知认产权单位属北京邮电大学学校有权保留并向国家有关部门或机构送交论文的复印件和磁盘,允许学位论文被查阅和借阅:学校可以公布学位论文的全部或部分内容,可以允许采用影印、缩印或其它复制手段保存、汇编学位论文。本人签名:日期:20°3.2导师签名:日期:100Gb/ s PM-QPSK相干光接收机载波频偏估计和相位恢复算法的研究摘要通信网络中高速率业务的不断发展,对现有的城域网络及省际、国际骨干通信网络的传输带宽提出了更高、更迫切的要求。从目前主流的1040Gbp光传输技术向100Gbs演进成为光传输技术的发展趋势。近年来大量研究表明,相位调制及相干接收是最具前景的100Gbs光传输方式。其中,采用相干接收技术的偏振复用QPSK( PM-QPSK传输系统最被业界认可。该系统的符号速率比比特率降低4倍,因此有较高的光谱利用率,且收发机结构相对简单实现相对容易。此外,信道中的各种损伤,如色散、载波频偏、相位偏移等导致的信号损伤,都能在接收机中通过电域的数字信号处理(DSP)来灵活地补偿。对调相信号,载波与本振间的频率和相位偏移会使信号产生较大的相位失真,频偏估计和相位恢复成为相干接收机中两个重要的功能模块。本文在国家863计划课题“1000b/s相干光传输关键技术研究(2009AA01Z221)”资助下,对上述系统接收机载波频偏和相位恢复算法展开了深入研究,主要内容如下:1.研究了 PM-QPSK的系统组成结构,重点研究了接收机DSP各组成模块的功能,并设计实现了相干接收机后端Maab仿真平台。2.详细分析了载波频偏估计算法,设计了算法并行处理实施方案以解决现有硬件处理速率不足够高的问题,并仿真验证了方案的可行性。设计了四次方频偏估计算法的并行结构;提出了基于误码性能反馈的 BA-PADE( BER-Aided pre-decision- based Angle DifferentialEstimator)算法,解决了传统PADE要求初始频偏设置与真实频偏接近的问题;提出了基于PADE的并行处理算法一一分组PADE( Grouped-PADE)。所设计方案均通过系统仿真验证了可行性。3.详细分析了载波相位恢复算法,为采用现有FPGA或DSP实现l00Gb/级信号处理,设计了载波相位恢复并行处理方案并仿真验证了方案的可行性。设计了基于Ⅴ iterbj- Viterbi的优化算法及其并行处理结构,将其同频偏估计并行算法联合进行了二进制定点仿真分析,仿真结果表明并行处理方案可显著降低硬件处理速率要求。关键词光传输相干接收频偏相位恢复THE RESEARCH OF FREQUENCY OFFSET ESTIMATIONAND PHASE RECOVERY ALGORITHMFOR 100Gbs OPTICAL COHERENT PM-QPSK RECEIVERABStRcTThe rapid development of high bit-rate services in communicationnetworks has instantly demanded a much higher bandwidth of coretransmission links in WAN, inter-province and international networks.The upgrade from the existing 10G/40G optical transmission to 100G hasbeen a trend. The research in recent years indicates that systems withphase modulation and coherent detection are the most promising, ofwhich PM-QPsk gets most recognitionThe PM-QPsK lowers the symbol rate as 1/4 of bit rate whichprovide high spectrum efficiency, and the transceiver structure ofPM-QPSK is simpler and so is easier to realize. Besides, with digitalalgorithms, the electrical Digital Signal Processing(DSP)in thee receivercan flexibly compensate the channel distortion caused by dispersion,carrier frequency offset and phase distortion. Since the phase distortioncaused by frequency and phase offset between lo and carrier is one ofthe main distortions in PM-QPSK, frequency offset compensation andphase recovery act as two of the core modules.With the support of National 863 Project"Research of the KeyTechnologies of 100Gb/s Optical Coherent Transmission Systems?", thisthesis mainly focuses on the research of the digital algorithms of carrierfrequency offset compensation and carrier phase recovery in the receiverof PM-QPSK system and the main contents are as follows1. Investigation of PM-QPSK structure, mainly on the receiver DSPstructure, including function of the several modules in this partDesigning and implementation of the Matlab simulation platform for theback-end of PM-QpsK receiver.2. Analysis on the carrier frequency offset estimation algorithmsdesigning of the parallel structure of the algorithms in order to break therestriction of hardware speed, with feasibility testified by simulationDesigning of the parallel structure of the 4 power method Designing ofBA-PADE (BER-Aided Pre-decision-based Angle Differential Estimator)based on BER feed-back to break the exact initialization restriction oftraditional PADE. Designing of a parallel operation scheme based onPADE, namely Grouped-PADE. Feasibility of both the forementionedscheme testified by simulation.3. Analysis on the carrier phase recovery algorithms, designing ofthe parallel operation scheme in order to realize phase recovery in100Gb/s PM-QPSK with current FPGA or DSP, with feasibility testifiedby simulation. Designing of the optimized and the parallel structure ofViterbi- Viterbi (V-V)method, and binary fixed-point simulation ofparallel v-v together with frequency offset algorithm, the result provedthat the scheme could observably lower the request to the hardwareoperation speedKEYWORDS optical transmission coherent detectionfrequency offset phase recovery
- 2020-12-05下载
- 积分：1
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