共查询到19条相似文献,搜索用时 109 毫秒
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电磁干扰(EMI)抑制技术是保证航天器各功能单元正常运行互不干扰的重要技术。开关电源是航天器内电磁干扰的主要来源。基于对星载开关电源DC/DC和负载点电源POL电磁干扰特性的测试结果,提出了一种星载二次电源系统的电磁干扰抑制方案,采用高稳晶振+控制器+时钟管理芯片硬件与软件设计结合的方法,利用高稳晶振为电源模块提供稳定时钟,通过控制器实现时钟管理芯片的分频和时钟分配。系统以非同步方式上电,软件控制时钟管理芯片输出电源模块同步时钟,然后软件打开时钟同步的使能,实现星载开关电源(DC/DC和POL)开关频率的外同步,最后通过测量输出电压频谱的方法验证了电磁干扰抑制方案的有效性。 相似文献
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出于对"低、慢、小"无人机进行导航定位诱骗的实际需求,在实验室原有的异步生成式GPS欺骗干扰源的基础上,研制了一种小型化的同步生成式GPS欺骗干扰源。首先,在异步生成式GPS欺骗干扰源射频信号模型的基础上,考虑到干扰源信号处理延时、欺骗信号的传播延时、无人机上目标接收机所接收真实卫星信号状态以及无人机运动模型,建立了对同步欺骗信号仿真时间和状态参数进行精确计算的数学模型。其次,通过本地授时型接收机提供驯服后的基准时钟和秒脉冲(1PPS)信号,实现欺骗干扰信号与真实卫星信号系统时的同步,并通过高阶直接数字频率合成(DDS)技术精确控制信号参数、保证欺骗信号到达目标接收机接收天线相位中心时与真实信号的相位状态在成功诱骗所允许的误差范围之内。最后,通过商用接收机和无人机进行了实验验证,在无人机上目标接收机正常跟踪真实卫星信号的前提下,开启同步生成式GPS欺骗干扰源发射欺骗信号,能够使目标接收机逐渐偏离正常定位测速结果而产生受控的定位测速结果。结果验证了同步信号模型和所设计同步信号生成电路的正确性,且表明同步生成式GPS欺骗干扰源能够实现对商用接收机和无人机导航定位的诱骗。 相似文献
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S/DB系统同步定时器的设计 总被引:1,自引:1,他引:0
龚德荣 《中国空间科学技术》1998,18(3):10-16
同步定时器是CDASS/DB系统的重要部件。它用高精度数字锁相环,精确地恢复地球同步气象卫星原始云图数据采集的同步基准信息。数字锁相环由用高速器件组成的相位比较器和用计算机软件实现的滤波器构成,采用标准频率计数方式,完成对精太阳脉冲(SP)和数字太阳——扫描同步检出(SSD)的锁相及星上时钟频率测量等任务。微机还兼作S/DB系统管理机。 相似文献
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就利用GPS技术实现中国VLBI网的高精度时频同步技术方案和其在天文学(天体物理、天体测量)、大地测量学、地球动力学(地球自转速率变化、地极移动、地壳形变、板块运动、地震)、空间科学和行星科学、时间频率比对及广义相对论检验等科学领域的重要应用进行了论证和介绍。 相似文献
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通过对一类混合系统仿真中的连续系统、离散事件系统及推理决策系统各自仿真时钟的分析,得出了推理决策系统仿真依赖于其他2个系统的结果,继而提出了用其中的离散事件系统仿真时钟去同步具有等步长策略的连续系统仿真时钟的等步长方法,并给出了相应的软件实现方法与性能评价准则,解决了该类混合系统仿真时钟的同步问题,从而为该类混合系统的仿真提供理论依据. 相似文献
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Wendong Meng Haifeng Zhang Peicheng Huang Jie Wang Zhongping Zhang Ying Liao Yang Ye Wei Hu Yuanming Wang Wanzhen Chen Fumin Yang Ivan Prochazka 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
High-precision time synchronization between satellites and ground stations plays the vital role in satellite navigation system. Laser time transfer (LTT) technology is widely recognized as the highest accuracy way to achieve time synchronization derived from satellite laser ranging (SLR) technology. Onboard LTT payload has been designed and developed by Shanghai Astronomical Observatory, and successfully applied to Chinese Beidou navigation satellites. By using the SLR system, with strictly controlling laser firing time and developing LTT data processing system on ground, the high precise onboard laser time transfer experiment has been first performed for satellite navigation system in the world. The clock difference and relative frequency difference between the ground hydrogen maser and space rubidium clocks have been obtained, with the precision of approximately 300 ps and relative frequency stability of 10E−14. This article describes the development of onboard LTT payload, introduces the principle, system composition, applications and LTT measuring results for Chinese satellite navigation system. 相似文献
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《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2020,65(3):978-996
Continuous and timely real-time satellite orbit and clock products are mandatory for real-time precise point positioning (RT-PPP). Real-time high-precision satellite orbit and clock products should be predicted within a short time in case of communication delay or connection breakdown in practical applications. For prediction, historical data describing the characteristics of the real-time orbit and clock can be used as the basis for performing the prediction. When historical data are scarce, it is difficult for many existing models to perform precise predictions. In this paper, a linear regression model is used to predict clock products. Seven-day GeoForschungsZentrum (GFZ) final clock products sampled at 30 s are used to analyze the characteristics of GNSS clocks. It is shown that the linear regression model can be used as the prediction model for the satellite clock products. In addition, the accuracy of the clock prediction for different satellites are analyzed using historical data with different periods (such as 2 and 10 epochs). Experimental results show that the accuracy of the clock with the linear regression prediction model using historical data with 10 epochs is 1.0 ns within 900 s. This is higher accuracy than that achieved using historical data of 2 epochs. Finally, the performance analysis for real-time kinematic precise point positioning (PPP) is provided using GFZ final clock prediction results and state space representation (SSR) clock prediction results when communication delay or connection breakdown occur. Experimental results show that the positioning accuracy without prediction is better than that with prediction in general, whether using the final clock product or the SSR clock product. For the final clock product, the positioning accuracy in the north (N), east (E), and up (U) directions is better than 10.0 cm with all visible GNSS satellites with prediction. In comparison, the 3D positioning accuracy of N, E, and U directions with visible GNSS satellites whose prediction accuracy is better than 0.1 ns using historical data of 10 epochs is improved from 15.0 cm to 7.0 cm. For the SSR clock product, the positioning accuracy of N, E, and U directions is better than 12.0 cm with visible GNSS satellites with prediction. In comparison, the 3D positioning accuracy of N, E, and U directions with visible GNSS satellites whose prediction accuracy is better than 0.1 ns using historical data of 10 epochs is improved from 12.0 cm to 9.0 cm. 相似文献
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Satellite positioning technology has been widely used in all kinds of military and civil land, marine, space and aeronautical target positioning tasks, naviga tion activities and accurate surveying measurements since 90 s in the last cen tury due to its advantage in providing all-weather, real-time, three dimensional and high precision positioning information, as well as speed and accurate timing information. By now, it has already formed a new hi-tech industry basically.This paper briefly reviews the development of the global satellite positioning and navigation technologies including the basic information of China's "Plough navigation system", introduces the history of satellite positioning technology and its major application fields as well as the status quo of this being industri alized trade in China, gives an account of the writers' vision for the application and prospect of the satellite positioning technologies in China, and approaches the tactics and stresses of the satellite positioning technology's application and its industrialization future in China. 相似文献
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Yang Yang Xiaokui Yue Jianping Yuan Chris Rizos 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Clock error estimation has been the focus of a great deal of research because of the extensive usage of clocks in GPS positioning applications. The receiver clock error in the spacecraft orbit determination is commonly estimated on an epoch-by-epoch basis, along with the spacecraft’s position. However, due to the high correlation between the spacecraft orbit altitude and the receiver clock parameters, estimates of the radial component are degraded in the kinematic approach. Using clocks with high stability, the predictable behaviour of the receiver oscillator can be exploited to improve the positioning accuracy, especially for the radial component. This paper introduces two GPS receiver clock models to describe the deterministic and stochastic property of the receiver clock, both of which can improve the accuracy of kinematic orbit determination for spacecraft in low earth orbit. In particular, the clock parameters are estimated as time offset and frequency offset in the two-state model. The frequency drift is also estimated as an unknown parameter in the three-state model. Additionally, residual non-deterministic random errors such as frequency white noise, frequency random walk noise and frequency random run noise are modelled. Test results indicate that the positioning accuracy could be improved significantly using one day of GRACE flight data. In particular, the error of the radial component was reduced by over 40.0% in the real-time scenario. 相似文献
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Qing Zhao Wang Gao Chengfa Gao Shuguo Pan Xing Yang Jun Wang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(3):1124-1142
The main challenge in real-time precise point positioning (PPP) is that the data outages or large time lags in receiving precise orbit and clock corrections greatly degrade the continuity and real-time performance of PPP positioning. To solve this problem, instead of directly predicting orbit and clock corrections in previous researches, this paper presents an alternative approach of generating combined corrections including orbit error, satellite clock and receiver-related error with broadcast ephemeris. Using ambiguities and satellite fractional-cycle biases (FCBs) of previous epoch and the short-term predicted tropospheric delay through linear extrapolation model (LEM), combined corrections at current epoch are retrieved and weighted with multiple reference stations, and further broadcast to user for continuous enhanced positioning during outages of orbit and clock corrections. To validate the proposed method, two reference station network with different inter-station distance from National Geodetic Survey (NGS) network are used for experiments with six different time lags (i.e., 5 s, 10 s, 15 s, 30 s, 45 s and 60 s), and one set of data collected by unmanned aerial vehicle (UAV) is also used. The performance of LEM is investigated, and the troposphere prediction accuracy of low elevation (e.g., 10–20degrees) satellites has been improved by 44.1% to 79.0%. The average accuracy of combined corrections before and after LEM is used is improved by 12.5% to 77.3%. Without LEM, an accuracy of 2–3 cm can be maintained only in case of small time lags, while the accuracies with LEM are all better than 2 cm in case of different time lags. The performance of simulated kinematic PPP at user end is assessed in terms of positioning accuracy and epoch fix rate. In case of different time lags, after LEM is used, the average accuracy in horizontal direction is better than 3 cm, and the accuracy in up direction is better than 5 cm. At the same time, the epoch fix rate has also increased to varying degrees. The results of the UAV data show that in real kinematic environment, the proposed method can still maintain a positioning accuracy of several centimeters in case of 20 s time lag. 相似文献
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星钟的频率稳定性决定了星钟提供时间信息的精度,而频率稳定性取决于星钟物理核心温度的稳定程度.基于RBF神经网络逼近星钟热模型,设计自适应PID控制方法实现星钟物理核心的温度控制.仿真验证了算法的有效性. 相似文献
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描述了一种可移动式铯原子钟的设计和性能。该装置可断续或连续运行,结构独特、潜力较大,在一定使用环境下,主要技术指标达到了国外商品铯钟相应的先进水平。 相似文献