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大口径射电望远镜电磁兼容评估技术研究
Alternative TitleResearch on EIC Evaluaiton for Large Diameter Radio Telescope
刘奇
Subtype博士
Thesis Advisor王娜
2019
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Name理学博士
Degree Discipline天文技术与方法
Keyword电磁兼容性,射电望远镜,电波环境,干扰电平限值,辐射评估,干扰缓解 EMC,radio telescope,emmision evaluation,interference level limit, RFI mitigation
Abstract电磁兼容性是设备或系统的重要性能指标,也是保障系统的工作效能和提高系统可靠性的重要因素。大口径射电望远镜运行阶段,台址周围无线电业务及内部潜在电磁干扰降低观测系统灵敏度,影响天文观测的质量。本论文针对拟建的新疆110m全向可动射电望远镜(QiTai raido Telescope,QTT),开展系统电磁兼容评估技术及控制方法研究,具有重要的工程应用价值。 首先,依据现有电波环境测量方法的不足,深入分析了仪器设备的关键参数配置方法及测量时间计算方法,采用Y因子法校准测量数据,提出一种准实时电波环境测量方法。面向高重复性宽带频谱,分析了宽带频谱信号和噪声特征,结合标准差理论,提出一种基于邻值比较的信噪分离方法,并采用邻值统计方法优化关键参数,提高信噪分离精度。针对QTT台址,开发了自动化电波环境监测系统,该系统6GHz以下频段,系统增益大于40dB,系统噪声系数小于2dB,测量不确定度小于1.47dB,具有极高的系统灵敏度和测量精度;分析了频谱监测数据流,设计了基于HDF5的数据存储格式,开发了自动化电波环境测量和监控软件和数据处理软件。依据QTT台址长期监测数据,评估分析了台址电磁环境、主要干扰源特征及其影响。 其次,提出大口径射电望远镜馈源口面干扰电平限值量化方法,建立了基于台址地形的电波传播模型,分析了现有电波传播模型的优缺点及适应性,结合QTT台址实际地形及地质特征,采用Longley-Rice和Two-Ray电波传播模型,预测分析了QTT台址潜在干扰区域电磁干扰达到射电望远镜的电波路径衰减,结合大口径射电望远镜天线增益量化方法,提出设备所在位置干扰电平限值量化方法,运用该方法对QTT台址潜在干扰区域的干扰电平限值进行量化。依据设备所在位置干扰电平限值,调研分析了国内外军用、民用电磁兼容测量标准,结合电磁干对射电天文观测的影响,提出一种大口径射电望远镜电磁兼容控制方法,解决了现有电波暗室测量系统无法直接测量评估电子设备电磁兼容的问题,该电磁兼容控制方法计划应用于QTT建设及运行阶段,确保系统拥有良好的电磁兼容性。 最后,依据QTT台址潜在干扰区域干扰电平限值,结合典型电子设备电磁辐射频谱,分析了QTT电磁兼容设计需求,提出电磁兼容设计初步方案。另外,针对台址建筑设施内中低电磁辐射干扰源,提出一种低成本建筑屏蔽方法,应用于QTT台址现有建筑。
Other AbstractElectroMagnetic Compatibility (EMC) is an important perfomance index of equipment or system, which is also an important factor to ensure the working efficiency of the system and improve the reliability of the system. For large diameter radio telescope constructing and operating stage, potential electromagnetic interference from the radio service around the site and the internal various types of electrics will affect the quality of certain observations or specific observation types, limiting the overallefficiency ofradio astronomical observations. This theis invesgated the electromagnetic compatibility evaluation technology for the proposed 110m diamter fully movable radio telescope in Xinjiang(QTT, Qi Tai radio Telescope), which has an important engineering application value. Firstly, according to the shortcomings of the existing radio environment measurement methods in radio astronomical field, the key parameters configuration and measurement time calculation methods for signal analyzer were analyzed deeply, we use Y-factor method for system gain measuring to calibrate RFI data, and a quasi-real-time radio environment measurement method is proposed. For broadband spectra, this thesis analyzed the characteristics of broadband spectra signal and noise, combined with standard deviation theory,a high precision signal-to-noise separation method based on neighborhood value comparison was proposed to realize signal extracted and counted effectively. Additionally, an automated, high-sensitive radio environment monitoring system was developed for QTT site. System perfomance testing data indicate that, below 6GHz, the system gain is greater than 40 dB, system noise figure is less than 2 dB, and the measurement uncertainty is less than 1.49 dB, which is sensitive enough for wealk signal detection. What's more, according to the data flow of spectrum monitoring, we designed a HDF5 data format for data storage, and a measurement and monitor software including a data processing software were developed for spectrum monitoring and data processing effectively. Based on the long-term monitoring RFI data, we evaluated RFI environment of QTT, and analyzed the main interference sources characteristics and their effects on observations as well. Secondly, we proposed an interference level limit quantified method for feed aperture of large diameter telescope. Then a radio wave propagation model based on QTT site terrain was established by analyzing the advantagesand disadvantages of the existing radio wave propagation methods. We used Longley-Rice and Two-Ray model to predict the path loss between the potential interference area and QTT. Combined with the proposed large diameter radio telescope antenna gain quantified method, the interference level limit of the potential interference area at QTT are calculated. Further more, we investigated and analyzed the EMC measurement standards, and an EMC evaluation method was estalbished for large diameter radio telescope with interference impacting on observations analyzed, which will be applied to the QTT construction and operation stage ensuring that the system has good electromagnetic compatibility. Finally, we calculated the EMC design requirements according to the interference level limit of potential interference areas, and the preliminary EMC design scheme for QTT was privided. Additionally, inder to mitigate the RFIs in facilities, we propose alow cost building shielding approach, which was applied to the existing buildings at QTT site.
Pages105
Language中文
Document Type学位论文
Identifierhttp://ir.xao.ac.cn/handle/45760611-7/2710
Collection研究生
Affiliation中国科学院新疆天文台
First Author AffilicationXinjiang Astronomical Observatory, Chinese Academy of Sciences
Recommended Citation
GB/T 7714
刘奇. 大口径射电望远镜电磁兼容评估技术研究[D]. 北京. 中国科学院大学,2019.
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