Subjects: Astronomy >> Astrophysical processes submitted time 2023-10-18 Cooperative journals: 《天文研究与技术》
Abstract: Type II radio bursts are the best tracers of Coronal Mass Ejections (CME). The coronal or interplanetary shocks are generated along with a dramatic effect on the Earth′s magnetosphere, when CME exceed the local Alfin velocity. The detection of type II radio bursts in the radio band manifests the generation of coronal shock waves. The prediction of the arrival time of shock waves to the Earth is essential to the space weather prediction. Type II radio burst was detected for the first time by Qitai low frequency (Qitai LFRA) at around 06:20 UT on September 28, 2021, with a frequency coverage of 18-50 MHz and a duration of more than 10 minutes. Since virtually no observation with effective spatial resolution have been made at extremely low frequency (<40 MHz) band, there is a great possibility to discover unknown phenomena at this band in future. Our observation shows that Qitai LFRA has good performance (Typical gain: 6 dBi) and high sensitivity(-78 dBm/125 kHz, DR: 72 dB), and can play a unique role in the 25th annual solar activity peak.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-01-17 Cooperative journals: 《天文研究与技术》
Abstract: The array antenna is placed at the focal plane of the radio telescope and combined with the beam forming network to observe a sky area at the same time to achieve greater field of view coverage. Because the amplitude and phase of each element need to be adjusted, the array antenna is actually a small phased array. Therefore, when designing the array, in addition to combining the focal field distribution of the telescope and the field of view to be achieved by the telescope, the performance verification of the array itself can refer to the traditional phased array. This paper designs a 2 × 2 rectangular microstrip patch antenna array with element spacing of 0.7 times the wavelength. The measured results show that the S11 of each port is all below -10dB, and the beam gain after the beamforming of 4 elements is 12.54dBi. By adding a delay line with a theoretical deviation of 30 degrees to the corresponding element, the beam scanning angle of the array is 28.3 degrees. Although the measured data are slightly different from the simulation results, which is related to array fabrication and feed port welding, the related work has accumulated experience for the design, development and testing of array antenna with more elements, and it has a good guiding significance for performance verification.
Subjects: Astronomy >> Astrophysical processes submitted time 2022-07-29 Cooperative journals: 《天文研究与技术》
Abstract: In order to solve the problem of non-uniform temperature thermal deformation caused by antenna alidade under solar radiation, environmental parameters, solar irradiation parameters and the geometric model of the alidade structure are derived, and the thermodynamic simulation of antenna alidade structure under multiply operating conditions is realized, and Based on the integrated model, the temperature characteristics of antenna alidade are analyzed. 24 fiber Bragg grating temperature sensors are installed on the antenna alidade structure, and the relative accuracy of the measured temperature and the simulated temperature field is higher than 85%, which verifies the correctness of the simulation method. Combined with the geometric relationship between the shift field of the antenna structure and the data of the deviation of the antenna azimuth axis and the measured temperature characteristic data, the rapid calculation of the deformation from measured temperature to the alidade structure is realized, and the causes of the deviation of the antenna alidade shaft are analyzed.
Subjects: Astronomy >> Astrophysical processes submitted time 2022-05-30 Cooperative journals: 《天文研究与技术》
Abstract:相控阵馈源是将阵列天线放置于射电望远镜焦面场处,用以实现更高增益及更灵活波束调控的接收机技术。鉴于其与阵列天线一样,是由多个天线单元以一定方式组合排列而成,工作时阵元之间产生电磁耦合在所难免。本文选用螺旋天线作为阵列天线单元,工作频率为1.25GHz,对独立天线进行仿真优化后,该天线-10dB阻抗带宽仅为70MHz。依托该天线单元建立55矩形排布螺旋天线阵列模型,分别选取阵元间距为1、0.5、0.25、0.125倍波长(1.25GHz@0.24m),以此验证不同阵元间距下的互耦效应对整个阵列带宽的影响。最终通过对各阵元输入阻抗进行匹配,仿真得到在0.25倍波长间距下,阵列中心阵子的-10dB阻抗带宽可扩展至550MHz,而阵列天线的带宽也基本表征了将其用作相控阵馈源的工作带宽。上述工作加深了对阵列天线带宽特性的理解,也为实际应用于射电望远镜系统的相控阵馈源实现更宽的工作带宽提供了可能。
Subjects: Astronomy >> Astrophysical processes submitted time 2021-09-29 Cooperative journals: 《天文研究与技术》
Abstract:快速射电暴(Fast Radio Burst,FRB)是目前射电天文领域的主要热点前沿。其相关研究被《自然》(Nature)杂志评选为2020年十大科学发现之一。FRB爆发时间极短且鲜少重复的特点,使其观测捕捉到的概率极低。由人工从海量的天文观测数据中识别FRB事件是件耗时费力的工作。机器学习技术的蓬勃发展为实时搜寻与多频段联合跟踪观测FRB带来了可能。该文从传统机器学习方法和深度学习方法两个方面,对该研究已有的成果进行了分析与总结,并探讨了基于机器学习的FRB搜寻技术目前存在的问题和面临的挑战,分析了其未来发展趋势。
Subjects: Astronomy >> Astrophysical processes submitted time 2021-09-29 Cooperative journals: 《天文研究与技术》
Abstract:射电天文接收机中频系统是接收机的重要组成部分,接收机的L、S、C、K波段的左圆极化和右圆极化信号在高频仓通过下变频成为中频信号。中频信号通过同轴电缆传送到观测室。观测室距离射电望远镜高频仓较远,因此线损较大,且不同频率的信号损耗不同,频率越高损耗越大,导致中频信号功率较小且增益平坦度随频率增加而降低。设计了四通道均衡放大模块,提高中频信号增益并补偿增益平坦度。该模块的均衡器采用了集总元件和微带线相结合的方式,具有结构紧凑、易于集成、成本低的优点。测试结果表明,在6倍频带宽内,均衡量≥8dB,均衡后功率平坦度≤3.5dBm,回波损耗≤-15dB,满足了射电天文中频检测系统的要求。
Subjects: Astronomy >> Astrophysical processes submitted time 2021-06-18 Cooperative journals: 《天文研究与技术》
Abstract: 射电天文是通过接收和处理无线电波以此研究宇宙天体的一门学科,微波接收机则是射电天文观测的核心接收设备。结合中国科学院新疆天文台南山25米射电望远镜现有K波段制冷接收机及未来Q波段毫米波观测需求,本论文提出一种K波段常温接收机研制,该接收机射频工作频率22-24.2GHz,经混频最终输出3.95-6.15GHz的中频信号,主要用于在K波段开展强度校准方法实践及大气不透明度测量。最终采用冷热负载法测试K波段常温接收机噪声温度为402.2K(理论计算为410.6K),标准噪声源为166.3K也满足设计需求,结合斩波轮校准机械结构,该K波段接收机已经具备开展强度校准及大气不透明度测试功能,相关工作也可为南山25米射电望远镜未来Q波段毫米波观测做技术预研。
Subjects: Astronomy >> Astrophysical processes submitted time 2020-05-12 Cooperative journals: 《天文研究与技术》
Abstract:噪声注入定标方法作为厘米波段一种常规强度校准方式而被广泛使用。通过组建K波段常温接收机及其定标平台,在室内20℃下使用传统冷热负载法标定接收机噪声温度及噪声源温度,之后在室外-7℃中使用同样方法再次标定上述参数,并利用室内标定的噪声源去进一步标定室外环境中接收机的噪声温度。测试结果表明,在环境温度变化约27度时,接收机噪声温度定标差异约为50.5%,标准噪声源定标差异约为41%。故此得知,如若将噪声注入法应用于常温接收机定标中,首先需考虑对接收机进行恒温处理,另外可采取对注入的标准噪声源进行温度补偿,使其可以更加精确的应用于二次定标当中,这也是本论文下一步计划开展的工作。
Subjects: Astronomy >> Astrophysical processes submitted time 2020-05-06 Cooperative journals: 《天文研究与技术》
Abstract:为实现宽频带电磁环境实时测量,基于Roach II开发平台,开发设计了数字频谱仪,实时带宽10MHz−2GHz,动态范围达到55dB。首先,分析了数字频谱仪开发设计理念和模块参数设置考虑,实现快速扫描模式、脉冲监测模式测试功能。其次,通过频率响应、动态范围、线性度等关键指标测量及分析,并与商用频谱仪测量结果对比,确定该数字频谱分析仪具有相对准确的测试精度,可应用于射电望远镜台站宽带实时频谱监测及瞬态信号分析。
Subjects: Astronomy >> Astrophysical processes submitted time 2020-04-09 Cooperative journals: 《天文研究与技术》
Abstract:针对新疆奇台110m全向可动射电望远镜(Qi Tai Radio Telescope,QTT)台址电磁环境监测系统,开发监测及数据处理软件,实现电磁环境自动化监测与高效数据处理,具有重要的工程意义。本文依据电磁环境监测系统测量需求,分析了软件开发的主要功能及关键技术问题,设计了基于HDF5数据格式的数据存储流程,采用多仪器并行控制及多线程并行处理技术,基于Microsoft Visual Studio开发平台,实现自动化电磁环境监测与高效数据处理软件的开发,并应用于QTT台址电磁环境监测系统。
Subjects: Astronomy >> Astrophysical processes submitted time 2019-04-17 Cooperative journals: 《天文研究与技术》
Abstract: 对新疆天文台(XAO)南山一米大视场天文望远镜(NOWT)观测的历史数据,我们进行细致的数据挖掘,发现了百余颗变源。数据处理pipeline为XAO时域巡天数据处理包,该处理包同时考虑了测光系统内部权重和相关性,并结合快速混合算法编写的。除去已知的变源,我们发现了很多新的变源。对新变源证认的过程中,我们将结果与LAMOST、GCVS、VSX、Gaia DR2等星表进行了交叉。在讨论部分,我们对各星表的使用情况给出了说明。对于新源最后发现绝大部分是食双星,少部分是脉动变星,并有一颗表现相对复杂的变源。
Subjects: Astronomy >> Astrophysical processes submitted time 2018-11-01 Cooperative journals: 《天文研究与技术》
Abstract: 新疆天文台望远镜所产生的观测数据通过数据专线传输到台本部数据中心进行长期存储。采用rsync进行数据传输,过程中没有详细的日志记录信息,无法对传输情况进行统计分析。本文通过调研新疆天文台数据传输需求,设计并开发了新疆天文台观测数据传输日志系统。系统以新疆天文台南山站、奇台站的数据存储服务器和台本部长期存储为基础,设计了日志系统的整体架构,实现了数据传输过程的日志记录。系统基于shell多线程技术、qt框架开发了后台服务程序及日志系统软件界面,实现了日志分析、统计备份与数据传输可视化页面。