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52.
在航空应用中,多卫星导航系统组合导航是未来的发展趋势,可用性是航空应用的主要性能要求之一。但是在截止角增大时,GPS单系统的可用性却达不到航空性能标准。针对该问题,对GPS/Galileo/BD组合系统在中国境内的可用性进行仿真分析,与GPS单系统相比,组合系统的可用性相对单系统有所提高,且截止角较大时,仍能达到可用性要求。 相似文献
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一种GPS/Galileo双模双频接收机射频前端芯片设计 总被引:1,自引:0,他引:1
提出了一种双频带混合GPS/Galileo接收系统,GPS与Galileo共同运作,规避了单一模式的安全漏洞,使卫星定位提供更稳定、更可靠、更安全的导航服务成为可能.接收系统同时接收GPS L1/L2和Galileo E1/E5a信号,提高了系统灵敏度,可以实现高精度定位和实时导航定位,同时能够最大限度地复用射频硬件资源,大大减少了芯片面积的消耗和系统功耗.通过系统参数仿真,各系统性能指标均满足设计要求. 相似文献
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Kerry V. Magruder 《Centaurus; international magazine of the history of science and medicine》2009,51(3):189-212
Abstract. Gabriele Beati (1607–1673) taught mathematics at the Collegio Romano when in 1662 he published an introduction to astronomy, the Sphaera triplex . This little work contains an interesting cosmic section which is analyzed here as representing a fusion of Jesuit traditions in cosmology achieved by Giovanni Battista Riccioli (1598–1671). The cosmic section enumerates three heavens, depicts fluid planetary heavens, and expresses hexameral biblical idiom. Woodcut and engraved variants of the cosmic section offer a glimpse of Jesuit freedom to experiment with various cosmological systems (Capellan, Tychonic and semi-Tychonic). Analysis of this cosmic section suggests several conclusions for the interpretation of visual representations, science and biblical interpretation, the Scientific Revolution and Jesuit science after Galileo. 相似文献
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伽利略导航系统将在E5频段发射交替二元偏置载波(Alternate Binary Offset Carrier,ALTBOC)信号,但国内外学者对其特性的研究还很不充分。基于随机信号分析理论,在对Galileo ALTBOC(15,10)信号各分量正交性证明基础上,提出采用多进制符号编码调制信号功率谱和正交信号功率谱公式推导Galileo ALTBOC信号的功率谱的新方法,并将其与传统双向偏移QPSK-R(10)信号功率谱近似算法进行比对,ALTBOC功率谱密度与双向偏移QPSK-R(10)功率谱密度最大差0.9 dB。 相似文献
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Hui Hua Chen Wei Min Jia Min Li Yao 《Wireless Communications and Mobile Computing》2014,14(15):1500-1508
Global Navigation Satellite Systems positioning accuracy indoor and urban canyons environments are greatly affected by multipath because of distortions in its autocorrelation function. In this paper, we propose a new multipath mitigation technique based on the concept of S‐curve shaping for the new alternative binary offset carrier (AltBOC)‐modulated signals, which will most likely be used in both European Galileo system and Chinese Compass system. The definition of an optimum S‐curve is employed to reduce the false lock points and to improve the multipath mitigation capability via determining the shape of the local code tracking reference function. The structure of the proposed code tracking loop for AltBOC signals is quite simple and only requires one complex correlator. Results demonstrate that the proposed technique provides superior multipath mitigation performance compared with the conventional receiver correlation techniques and removes the ambiguity completely. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Comments on an article (see record 2007-14606-004) by A. Machado and F. J. Silva, who claimed that psychology's current conception of scientific method comprises two clusters of activities: experimentation and mathematization. They proposed that psychology needs to enrich its accounts of scientific method with a third cluster of activities that they call conceptual analysis. Haig agrees with the authors that psychology needs to improve its understanding of scientific methods, but he believes that giving greater attention to conceptual analysis is not the appropriate way to do this. In this comment, Haig suggests that conceptual analysis as such is not a distinctive feature of scientific method. He maintains instead that the most appropriate way to enrich our understanding of scientific method is to develop better theories of scientific method. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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