共查询到20条相似文献，搜索用时 562 毫秒
1.
李明华 《成都信息工程学院学报》2000,15(3):231-236
提出了一种格形编码的正交频分复用 (TC OFDM )方案 ,研究把正交频分复用(OFDM )和格形编码 (TCM )有机地结合 ,来克服时间色散信道中的频率选择性和多径衰落。对码率 2 / 3格形编码的 8DPSK OFDM在时间色散信道中的误码率性能进行了分析和模拟 ,讨论了不同正交载波数情况下格形编码的设计。结果表明 ,在比特误码率BER为 10 - 3时采用TC OFDM方案与未编码系统相比可以提供 6dB的编码增益。 相似文献
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王浩 《大地测量与地球动力学》2007,27(Z1):140-142
阐述了适合高速无线数据传输的正交频分复用(OFDM)调制方式的基本原理及调制解调的快速傅立叶变换(FFT)实现,并给出OFDM基带处理系统的结构图和硬件模块框图。 相似文献
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正交频分复用（OFDM）系统的一个主要缺点是峰均功率比（PAPR）过高.选择映射法（SLM）是一种有效的降低OFDM系统的峰均功率比的方法.采用一种改进的选择映射法,把降低峰均功率比和信道编码相结合.仿真结果表明,不仅能够降低OFDM系统的峰均比,而且系统的误比特性能也得到提高. 相似文献
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正交频分复用(OFDM)作为一种可以有效对抗符号间干扰(ISI)的高速传输技术,得到了广泛的应用,而信道估计技术作为其重要技术之一得到了很大的发展.信道估计分为盲信道估计、半盲信道估计和基于导频的信道估计.主要研究基于导频的最小平方(LS)信道估计和线性最小均方误差(LMMSE,Linear Minimum Mean Square Error)信道估计,在不同的信道环境和不同的循环前缀(CP)和导频子载波数下的性能比较并得出结论. 相似文献
5.
跳频与同频复用是移动通信系统中重要的两种应用技术。简介跳频技术与同频复用的基本原理，并着重分析了在实际应用中跳频与同频复用相结合的几种方式。 相似文献
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提出了一种改进的正交频分复用（Orthogonal Frequency Division Multiplexing,OFDM）载波频率偏移估计算法并通过MATLAB进行仿真.仿真结果表明算法对小数载波频率偏移估计精度高并且其算法复杂度低. 相似文献
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多输入多输出（MIMO）技术是最近几年发展起来的无线通信技术。目前利用MIMO技术提高短波通信的传输速率和可靠性的研究已经开展。着重研究了MIMO OFDM（交频分复用）短波无线通信的同步技术，利用截断的Suehiro序列构成的训练符号完成了系统的同步捕获。仿真结果标明，与Mody算法相比，该方案在性能相近的情况下可提高系统的频谱效率。 相似文献
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提出了海陆一体机载激光扫描仪设计方案。采用高频双波长激光以及大动态接收光路,实现地貌与水深的联合探测;采用基于自校准时间数字转换,重构高精度的点云数据;采用基于编码正交频分复用调制解调技术,实现机载点云探测数据的快速回传。 相似文献
9.
魏艳华 《成都信息工程学院学报》2007,22(1):84-87
跳频通信是一种有效的抗干扰通信技术，跳频序列的性能对跳频通信系统的性能有着决定性的影响。重点阐述了RS码作为跳频序列的编码方法及其性能，介绍了RS码序列的具体编写方法，并进行了计算机仿真，计算了所生成RS跳频序列的汉明相关性能。 相似文献
10.
汶东凹陷古近系分为古新世固城组和始新世大汶口组。大汶口组又分上、中、下3段，相应有3个化石组合带。从地震反射看，该凹陷内自下而上呈5组反射波特征。以古近纪地层特征为基础，结合构造演化分析认为：固城组为干旱气候条件下的山麓洪积相沉积，大汶口组下段为干旱条件下浅湖相沉积，大汶口组中段为逐渐湿润条件下的氧化一还原湖相沉积，大汶口组上段为潮湿气候条件下的还原湖相沉积。 相似文献
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The ability of cell to modulate the fluidity of plasma membrane was crucial to the survival of microorganism at low temperature. Plasma membrane proteins, fatty acids and carotenoids profiles of Antarctic psychrophilc yeast Rhodotorula sp. NJ298 were investigated at -3 ℃, 0 ℃ and 8 ℃. The results showed that plasma membrane protein content was greater at -3 ℃ than that at 8 ℃, and a unique membrane polypeptide composition with an apparent molecular mass of 94.7 kDa was newly synthesized with SDS-PAGE analysis; GC analysis showed that the main changes of fatty acids were the percentage of unsaturated fatty acids (C18∶ 1 and C18∶ 2) and shorter chain saturated fatty acid (C10∶ 0) increased along with the decrease of the culture temperature from 8 ℃ to -3 ℃; HPLC analysis indicated that astaxanthin was the major functional carotenoids of the plasma membrane, percentage of which increased from 54.6±1.5% at 8 ℃ to 81.9±2.1% at -3 ℃. However the fluidity of plasma membrane which was determined by measuring fluorescence anisotropy was similar at -3 ℃, 0 ℃ and 8 ℃. Hence these changes in plasma membrane's characteristics were involved in the cellular cold-adaptation by which NJ298 could maintain normal plasma membrane fluidity at near-freezing temperature. 相似文献
13.
《极地研究(英文版)》2014,(4)
正1 Aims and Scope Advances in Polar Science(APS)is an international,peer-reviewed journal jointly sponsored by the Polar Research Institute of China and the Chinese Arctic and Antarctic Administration.APS is a comprehensive academic journal dedicated to presentation of multi-disciplinary achievements in Arctic and Antarctic expeditions and research.Its primary purpose 相似文献
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《中国海洋大学学报(英文版)》2014,(4)
<正>Copyright Submfnion of a roanusatpt inks:that the work described has not been published before(exoept In the form of an abstrW or as part of a published lecture,review,or thesis);that it is not under consideration for publication elsewhere that its publication has been approved by ail 相似文献
15.
《中国海洋大学学报(英文版)》2014,(6)
<正>The Journal of Ocean University of China(Oceanic and Coastal Sea Research)is a comprehensive academic quarterly sponsored by the Ocean University of China,published one volume per year.This journal is devoted to the publication of the theoretical and applied research results on oceanography and marine fisheries.The fieldcovered include the physical,chemical,biological,geo- 相似文献
16.
Massimo GRECO 《山地科学学报》2014,(6):1383-1384
<正>The 35th IAHR World Congress was held in Chengdu,China from September 8 to September 132013.The title of the conference was:"The Wise Finds Pleasure in Water:Meandering through Water Science and Engineering".During the congress,1239 papers were presented in 139sessions for oral presentations and 7 sessions for poster presentations.After the Congress,a Committee was appointed to select some of the best papers presented at the Congress for publication,after a 相似文献
17.
As an important component of the cryosphere,sea ice is very sensitive to the climate change.The study of the sea ice physics needs accurate sea ice thickness.This paper presents an electromagnetic-induction(EM) technique which can be used to measure the sea ice thickness distribution efficiently,and the successful application in Bothnian Bay.Based on the electromagnetic field theory and the electrical properties of sea ice and seawater,EM technique can detect the distance between the instrument and the ice/water interface accurately,than the sea ice thickness is obtained.Contrastive analysis of the apparent conductivity data obtained by EM and the value of drill-hole at same positions allows a construction of a transformable formula of the apparent conductivity to sea ice thickness.The verification of the sea ice thickness calculated by this formula indicates that EM technique is able to get reliable sea ice thickness with average relative error of only 12%.The statistic of all ice thickness profiles shows that the level ice distribution in Bothnian Bay was 0.4-0.6 m. 相似文献
18.
Based on the hydrographic data in austral summer during the 22nd Antarctic Expedition of China(2005/2006),some features can be found about the northern margin of Emery ice shelf as follows.The heat content in the surface layer(0-50 m) at the eastern end and the western end of the ice-shelf margin is much higher than that at the middle.The upper mixing-layer depth and the seasonal thermocline depth at the middle of the ice-shelf northern margin are much shallower than those at the both ends.However there is much less difference between the middle and the ends in the bottom layer.The remote sensing photos show that the inhomogeneity in the surface-layer water is closely related to the spatial distribution of the floes and polynia in the area. 相似文献
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正Rapid changes of Arctic sea ice cover have been in the focus of the international climate research community in recent years.Quite a few of nations have completed a large number of related surveys and research projects in the Arctic Ocean.Up to now,China has performed six research cruises to the Arctic Ocean resulting in a significant volume of research output.Improved knowledge on the atmospheree-sea ice-ocean interactions in the Arctic is a 相似文献
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