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针对直升机卫星通信系统中直升机旋翼对通信信道造成的周期性衰落问题,采用射频收发器AD9361模拟了信道周期性衰落模型,基于此模型在现场可编程门阵列(Field Programmable Gate Array,FPGA)上优化并实现了缝隙检测算法。根据信道衰落模型和缝隙检测算法及数据链路速率和带宽的要求,提出了一套直升机卫星通信系统可靠通信方案,即前向链路采用重发和分集接收及短码LDPC编码技术,返向链路根据前向链路缝隙检测的结果在无遮挡缝隙采用突发通信和长码低密度奇偶校验(Low Density Parity Check,LDPC)编码技术,实现可靠通信。系统测试结果表明,该方案不受直升机机型限制,系统可在40%遮挡率下实现前向链路25.6 kb/s和返向链路4 Mb/s速率下的可靠通信。 相似文献
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针对海上卫星通信终端在性能调试、系统联试和试验现场环节中关键特性的快速检测需求,设计和开发了一套便携式测试系统。测试系统可模拟生成码片速率为3.069 Mchip/s的星地前向扩频信号,接收解调数据速率最大为2.0 Mb/s的返向正交相移键控(Quadrature Phase Shift Keying,QPSK)调制信号,且具备快速检测终端捕获和跟踪卫星信号时间是否优于7.0 s的能力。采用软件无线电思想,基于Matlab的卫星信号模拟程序替代现场可编程门阵列(Field Programmable Gate Array,FPGA)完成数据的组帧、加扰和扩频处理,降低了测试系统开发难度和周期,并提高了适应性和灵活性。各阶段的应用结果表明,便携式测试系统能够快速测试卫星通信终端的关键特性,为现场及时发现并定位问题提供了可靠依据。 相似文献
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本文介绍一个用于跟踪与数据通信卫星系统的用户终端的K波段宽带收发信机,它利用多频段相参本振源、QPSK调制、毫米波混合集成技术实现相参宽带数据收发,并为数据处理终端提供各种调制方式的高速数传接口。本文主要介绍该收发信机设计原理及特点,以及各主要部分的实现方法。收发前端的各项技术指标都达到了设计要求。 相似文献
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TDRSS多模式调制器可产生多种模式的调制信号,在工程中具有较大的实际应用价值.对跟踪与数据中继卫星系统(TDRSS)信号形式进行了简单分析,针对多模式调制器的设计,介绍了硬件平台的选择、FPGA内的设计实现,并重点分析了几项关键指标. 相似文献
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《中国对外贸易(英文版)》2008,(5):50-51
The overall strategic relationship between U.K. and China is "better than ever", China- Britain relations have maintained good momentum, with increased high-level exchanges and the reinforcement of strategic mutual trust, with more room for growth in the future. 相似文献
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Guo Yan 《中国对外贸易(英文版)》2008,(5)
Domino effects of the global finance agitation As the origin of the subprime crisis,US financial institutions lost USS45 billion last year,accounted for over half of the total US,EU & Japan loss.Since January 15th,Chtigroup released its financial statement of the 4th quarter,showing a net deficit of USS9.83 billion,which marked the hisoric high of its quarterly deficit. 相似文献
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《中国对外贸易(英文版)》2008,(6):62-65
Among the Fortune 500 firms,more and more images from China emerge out.On the 2008 list,Sinosteel Corporation,a landmark group of China industries quietly squeezes into the candidate line.As the largest steel service & trade enterprise,its sales reached at RMB 111.24 billion,with a year-on-year increase of 83.03 percent,and the profit grew by 180.03 percent.On the Sinosteel 2008 Work Meeting,the president Huang Tianwen uttered,"In the coming year,we will work for US$20 billion sales,and look forward to getting a position in Fortune 500 firms for ourselves." 相似文献
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Zang Kejia 《中国对外贸易(英文版)》2008,(7):16-17
When the 103rd Canton Fair is approaching, an old friend of Canton Fair, Li Ying from Jiangsu prov-ince recollected his past five years' experiences to the grand trade meeting. Each year is special, with some unforgettable memories colored by the year. 相似文献
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Estaing, former French president, Valery Giscard d'Estaing attended Sino-French Economic Seminar held in Shanghai in early April and said that the world center has shifted from the west to the east with many European and US companies entering into Asia, and China has the ability to play an important role in the world stage. Estaing, naming himself"French Confucian", then said in Chinese that a cook-group includes 10 people in ancient Chinese soldier system and the cook is in charge of cooking for them. And people who belong to the same cook are actually "Partners". 相似文献
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《中国对外贸易(英文版)》2008,(5):12
The annual meeting of the World Economy Forum was held in Davos,a little town in Switzerland,on January 23rd to the 27th this year,with the theme"the Power fo Collaborative Innovation",over 2500 celebrates from ture political and cconomic circles of more than 80 countries and challengred logether to talk about the future of the global economy in 2008,A Forum for the problems and challenges that face whole world,some of the keywords which drew attention during the event were:the U.S.subprime mortgage crisis,soaring energy prices,the economic slowdown in the U.S.ermerging economic bodies,authority funds and the general unpredictable nature of the global economy. 相似文献
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"If you are considering to trade with companies in Japan or expanding your business to Japan we are ready to help from the very beginning."You will find this greeting at the first sight on the Chinese website of Japan External Trade Organization 《中国对外贸易(英文版)》2008,(10):16-17
If you are considering to trade with companies in Japan or expanding your .business to Japan, we are ready to help from the very beginning." You will find this greeting at the first sight on the Chinese website of Japan External Trade Organization (JETRO). JETRO has committed itself in delivering highly efficient and quality services to meet the demand of internal and external customs including Japanese companies, hence winning a good reputation in the international trade arena. In recent years, with its priority in advancing business cooperation in South and East Asia, JETRO has made great achievement in promoting trade between China and Japan. Therefore, China's Foreign Trade interviewed Mr. Yoichi Maine, Deputy Director General of JETRO BEIJING. 相似文献
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Guo Yan 《中国对外贸易(英文版)》2008,(12):62-63
Looking at the increasingly fierce competition in the world auto market. global automobile manufacturing industry, taking Europe, the U.S. and Japan as representatives, is gradually forming a new type of relationship, mutual cooperation between whole vehicle and parts manufacturers. We can clearly see that auto parts manufacturers have become independent from the whole vehicle manufacturing companies, which means that the former structure of auto industry has greatly changed, and a new relationship, 相似文献
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Guo Yan 《中国对外贸易(英文版)》2008,(1):10-10
In the middle of last December, the key purchase contracts for coal used in power generation in 2008 were signed, reflecting a demand for more than 1.085 billion tons. It is important to note that the country's five biggest power producers, China Huaneng Group, China Guodian Corporation, China Power Investment Corporation, China Huadian Corporation and China Datang Corporation, had settled on the prices on their purchase contracts, and they are expected to consume 290 million tons of coal for generating electricity, 相似文献
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Liu Xinwen 《中国对外贸易(英文版)》2008,(7)
Last year,the volume of China's auto trade reached US$66.878 bil- lion,of which imports accounted for US$25.982 billion,a year-on- year increase of 24.45 percent;while ex- ports totaled US$40.896 billion,growing by 45.31 percent.The China Association of Automobile Manufacturers(CAAM) predicts that the number of autos sold in 2008 will break the 1 million barrier for the first time in history,representing an increase of about 20 percent. 相似文献