共查询到20条相似文献,搜索用时 62 毫秒
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俞德育 《卫星电视与宽带多媒体》2005,(6):56-57
经过各部门多方深入细致研究,明年上半年即将发射的我国自行研制直播卫星(鑫诺2 号)已确定将采用圆极化波方式。另据2004年6月11日法国阿尔卡特宇航公司(Alcatel Space)发布的消息,中国卫星通信集团公司(ChinaSat)与阿尔卡特宇航公司草签合同,向法方订购的中星9号(ChinaSat-9)广播电视直播卫星也是采用圆极化工作方式(该星计划2007年由中国长征3号乙火箭发射,当年投入使用,定点轨位是92.2°E,并称该星将和我国鑫诺2号(SinaSat-2)一超构成中国第一代广播电视卫星直播系统,同时也将用于2008年北京奥运会的广播电视转播)。现就卫星工作的极化问题进行一些技术性讨论,尤其重点讨论圆极化问题, 可供今后接收我国直播卫星信号和商界研制产品时参考。 相似文献
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《数字通信世界》2005,(5):51-51
4月21日,阿尔卡特宇航公司与中国卫星通信集团公司(简称“中国卫通”)签署了一项价值1亿欧元的合同。按照合同,阿尔卡特将为中国卫通设计并制造新一代的通信直播卫星——“中星9号”。这颗直播卫星将使中国卫通成为中国提供卫星广播服务的主要运营商之一。中国卫通总裁张海南先生、阿尔卡特宇航公司董事长兼首席执行官苏睿思(Pascale Sourisse)女士,分别代表中法两方在合同上签字。基于阿尔卡特Spacebus 4000 C1卫星平台的“中星9号”是一颗大功率广播电视直播卫星,将配备22台有效Ku波段转发器提供广播卫星服务(简称BSS),包括18个36兆赫兹和4个54兆赫兹频道。“中星9号”卫星发射时的重量将达到4,500 相似文献
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王莉 《卫星电视与宽带多媒体》2007,(8):23-23
中国直播卫星有限公司(直播星公司)于3月30日至4月1日参展第15届中国国际广播电视信息网络展览会(CCBN2007),该公司未设单独展台,而是与中国卫星通信集团(中国卫通)、鑫诺卫星通信有限公司(鑫诺公司)展台以“三合一”的形式搭建在一起。据称,这是我国首家专业从事直播卫星运营的企业第一次正式公开亮相。国家广电总局副局长赵实、张海涛、胡占凡、田进、科技司司长王效杰等 相似文献
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2006年对广播电视业和卫星业来说将有一件共同的大事,那就是直播卫星上天。 相似文献
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Jee-Hoon Lee Jung Man Hwang Dong Hyuk Choi Seong-Ook Park 《IEEE transactions on information technology in biomedicine》2009,13(3):400-404
This paper proposes an integrated hypersensitive Doppler radar system through a circular polarization characteristic. Through the idea of a reverse sense of rotation when the reflecting surface is perfectly conducting, it is shown that the detecting property of the system can be effectively improved by using antennas that have a reverse polarization. This bistatic radar system can be used in noninvasively sensing biosignals such as respiration and heart rates with the periodic movement of skin and muscle near the heart. The operating frequency of the system is in the X-band and the radar size is 95 times 50 times 13 mm3. 相似文献
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Land mobile systems currently use vertically polarized antennas while trying to solve the problem of small sector signal variations, which are greater for vertical polarization than for either horizontal or circular polarization; This difference in small sector variations is shown from results of tests at 430 MHz. The variations at 900 MHz should be more rapid and have amplitudes at least as great as those shown for 450 MHz. At 900 MHz antennas can be made small for mobile service and the improvements noted here may spur developments in circularly polarized antennas. 相似文献
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本文介绍一种宽带圆极化微波电视全向发射天线,该天线具有频带宽,结构简单,体积小,重量轻,便于安装,成本低等特点,已应用在多个微波电视传输工程中。 相似文献
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激光诱导击穿光谱(LIBS)是一种快速、实时的元素成分分析技术。为了提高LIBS的灵敏度,人们已经提出多种方法来提高LIBS的光谱强度。本文采用飞秒脉冲激光烧蚀黄铜产生LIBS,对比了圆偏振和线偏振下LIBS光谱的强度,结果发现圆偏振下的光谱强度比线偏振下的强,光谱强度大约提高了15%。采用飞秒激光照射金属时,金属内部的自由电子吸收光子的能量。在线偏振飞秒激光场中,电子在脉冲的每个光学周期中经历交替的加速和减速;而圆偏振飞秒激光可以连续加速电子,因此电子可以获得更高的能量,这使得圆偏振飞秒激光产生的光谱强度不同于线偏振飞秒激光产生的光谱强度,圆偏振激光有助于改善飞秒LIBS信号的强度。 相似文献
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《Broadcasting, IEEE Transactions on》1982,(2):65-72
In this paper a new dipole-panel for circular polarized TV arrays is presented. The numerical analysis and the experimental tests performed upon this basic source show that it exhibits very good characteristics of axial ratio over a frequency band of the order of ±15%. Perhaps the most important feature of the dipole-panel is its high degree of componibility when it is used as a unit building-block in the synthesis of TV antenna arrays: smooth circular horizontal patterns have been realized with four-, five-and six-face arrays. Moreover, the possibility of synthesizing patterns different from the omnidirectional one, such as the cardioid pattern and the kidney pattern, shows that this dipole-panel is able to cover a very wide range af practical pattern shapes. To illustrate these features, a collection of numerical and experimental data are presented. 相似文献
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本文介绍了水平极化和圆极化两种天线的特点和参数,通过当地发射台安装的两副不同极化天线,在相同环境条件下收测其覆盖场强,将收测的数据进行对比,分析了两副天线的覆盖效果,并据此对调频广播发射天线的更新换代提出建议. 相似文献
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Jayashree P. Shinde Raj Kumar Mahadev D. Uplane 《Wireless Personal Communications》2014,75(2):843-856
A novel circular polarization (CP) design of a single-feed Hexagonal shaped microstrip antenna for enhanced antenna parameters is presented. The CP design is obtained by placing three isosceles triangular defects at proper locations in the hexagonal radiating patch as well as in the square ground plane. By adjusting one of the side lengths of the triangular defect, slightly longer or shorter than that of the others, two orthogonal near degenerate resonant modes for CP radiation are excited. Moreover, the 3 dB axial ratio bandwidth is surrounded by the 10 dB impedance bandwidth, to ensure that the antenna radiates CP waves in its impedance band. The antenna gain of the proposed antenna has increased by 5.34 dB (7.93 vs. 2.59 dB), as compared to the hexagonal microstrip antenna with triangular truncations in patch but without triangular defects in the ground plane having same substrate material, height and same radiating patch size and shape. Prototype antenna is fabricated for experimental evaluation. Simulated and measured results are in good agreement with each other. 相似文献