共查询到20条相似文献,搜索用时 93 毫秒
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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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Chun Yi 《中国对外贸易(英文版)》2008,(6)
In recent years.China's public finance put social construction high on the agenda and attaches more importance on livelihood insurance and improvement.The 2003-2007 public financial expenditure reflects a fact that the government isputting more emphasis on livelihood andissues concerning the people. 相似文献
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《中国对外贸易(英文版)》2008,(6)
"Crucial for economic growth.energy utilization has its role in all economic sectors and every aspect of people's daily life.Now we are in dire need of a new profession,namely energy manager.We not only need to have passion and responsibility,but also a scientific approach to conserve energy and cut emissions.APpropriate legislation should be in place.and a special profession should be introduced to ensure the implementation of these laws and regulations." 相似文献
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According to Ma Kai's economic planning report submitted to the NPC session on March th. 《中国对外贸易(英文版)》2008,(6):15-15
According to Ma Kai's economic planning report submitted to the NPC session on March 5th,(Ma Kai is the Minister in charge of the National Development and Reform Commission),the government has listed the slowdown in trade surplus growth and the steady expansion of external investment as major tasks for 2008. 相似文献
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《中国对外贸易(英文版)》2008,(1):64-67
A bout fifty years ago. a baby's cry broke the sky of quietness, in a small and beautiful town of Hunan province, which surroundcd by green hills and clear water. Though his .birth brought his family great happiness and hope just as any new life, nobody knew that the little boy would get great achievement when he grow up. even start his business oversea, and earn international honor. Let's share with you the entrepreneur Ouyang Riping's story, which may insights thcsc people who want to succeed and complete oneself in favorite condition or adversity rather leave things to so-called fate. 相似文献
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Liu Xinwen 《中国对外贸易(英文版)》2008,(5):44-45
"In recent years, we've found increasing interest from Chinese investors in the Belarus economy. Please let China know, Belarus is always ready to be a true friend to China. We have built a fort in Europe for China," the President of Belarus, Alexander Lukashenko told Zhou Xiaochuan, President of the Bank of China, during his visit to the capital of Minsk, on January 8th, he expressed his high praise and firm confidence in the development of Sino-Belarusian relations. 相似文献
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《中国对外贸易(英文版)》2008,(5):34-35
Similar to what the Christmas Day means for the westerners,the Spring Festival is the most important celebration for Chinese people.This big event according to Chinese traditional lunar calendar relaxes and pleases the whole country as the happiest gathering time of the year.National-wide crusade for going back home,too-difficult-to-get train tickets,generous family-going-out shopping,Miaohui laundering,New Year Eve reunion dinner,visiting friends and relatives,watching annual TV gala......each piece of clue reminds us of the smell of Chinese Spring Festival. 相似文献
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《中国对外贸易(英文版)》2008,(5):21
FDI(Foreign Direct Investment),a component of a country's national financlal accounts,is investment of foreign assets into domestic structures,equipment,and organizations.It does not include foreign investment into the stock markets,concession and subcontract.FDI iS thought to be more useful to a country than investments in the equity of its companies because equity investments are potentially "hot money"which can leave at the first sign of trouble,whereas FDI is durable and generally useful whether things go well or badly. 相似文献
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Holding percent of train media resources across China based on "Time Cube" on the Intermedia Recommendation Introduction Meeting on December HTC announced its high-profile strategy of tour marketing tapping the immeasurable potentials on the train. Meanwhile HTC officially launched its brand new product Olympic Train on the meeting providing a fabulous platform for all the brands that are prepared to do a smart marketing on the occasion of Olympic Games.…… 《中国对外贸易(英文版)》2008,(1):58
Holding 88 percent of train media resources across China, based on "Time Cube", on the 2008 Intermedia Recommendation and Introduction Meeting on December 19, 2007, HTC announced its high-profile strategy of tour marketing and tapping the immeasurable potentials on the train. Meanwhile, HTC officially launched its brand new product Olympic Train on the meeting, providing a fabulous platform for all the brands that are prepared to do a smart marketing on the occasion of 2008 Olympic Games. 相似文献
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Audrey Guo 《中国对外贸易(英文版)》2008,(1)
In the end of 2007, Air China Limited (hereinafter "Air China") and Shanghai Airlines, formally joined Star Alliance at a ceremony held in the new Terminal Three at Beijing Capital International Airport. With the addition of the two Chinese airlines, Star Alliance now has 19 member carriers operating 17,000 daily flights to 897 destinations in 160 countries. 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