暗能量探测专用宽带馈源研制
发布时间：2019-05-23 02:45
【摘要】：暗能量研究是当代科学研究中的重大前沿问题，现代宇宙理论认为，通过射电观测手段，对宇宙大尺度结构进行精密测量，利用其空间功率谱中的重子声学振荡特征测定不同红移处宇宙的膨胀速度，，可实现暗能量的探测。本文依据中国科学院国家天文台所提出的“天籁计划”，探索一种专用宽频带馈源的设计方法，研制在400MHz~1400MHz频带范围内均保持良好电性能的新型宽频带馈源，满足天籁计划要求。 论文在对比分析国内外天线阵及宽频带馈源研究现状基础上，指出了当前宽频带馈源在225MHz~750MHz频段时，远场辐射方向图对称性较差、回波损耗较大、匹配性不好等缺陷。通过引入反射面天线工作原理和电磁场理论，分析了天籁计划射电望远镜阵列中宽频带馈源的特殊指标，提出减少旋转抛物面天线与馈源相互影响的方法。 设计了一款四方板宽频带馈源，通过三维电磁仿真软件CST的仿真分析与结构优化、实物制作和性能测试，结果表明在低频段400MHz~1200MHz范围内，具有非常好的宽频性能也可保证天线阵列的高效率，但在高频段1200MHz~1400MHz内，馈线和四方板宽频带馈源匹配性能变得很差。为此，设计了改进折叠型的宽频带馈源，经仿真分析、结构优化、制作和性能测试，获得一款理想的宽频带馈源结构型式，实测表明在400MHz~1200MHz频带内具有非常好的宽频性能，其回波损耗低于-10dB，电压驻波比（VSWR）小于2.5，带宽约为50%，较好地满足了天籁计划项目的技术要求。 本文最后利用三组6m口径单元抛物面天线进行实验研究，为保证抛物面天线具有理想的波前，馈源装调过程中使相位中心与抛物面天线的焦点重合。实验中主要通过馈源和标准噪声源的切换来测定系统温度，测得系统温度大约为70K；用抛物面天线系统观测太阳、CygA、Cas A等射电源，得到了较好的干涉图样，将观测数据和模拟数据进行比较，从干涉条纹的斜率上看两者几乎完全吻合，说明宽频带馈源——抛物面天线系统的一致性非常好。 本文所提出的宽频带馈源及其试验方案，有利于馈源宽频带问题的深入研究，为“天籁计划”的宽频带馈源提供了优选方案。
[Abstract]:The study of dark energy is an important frontier issue in contemporary scientific research. according to modern cosmic theory, the large-scale structure of the universe is accurately measured by means of radio observation. The expansion velocity of the universe at different red shifts can be measured by using the baryons acoustic oscillations in its spatial power spectrum, and the detection of dark energy can be realized. According to the "sounds of Nature Plan" put forward by the National observatory of the Chinese Academy of Sciences, this paper explores a design method of special broadband feed, and develops a new broadband feed which maintains good electrical performance in the range of 400MHz~1400MHz frequency band, which meets the requirements of the plan. Based on the comparative analysis of the research status of antenna array and broadband feed at home and abroad, this paper points out that when the broadband feed is in 225MHz~750MHz band, the symmetry of far-field radiation pattern is poor, the echo loss is large, and the matching is not good. By introducing the working principle of reflector antenna and the theory of electromagnetic field, the special indexes of broadband feed in the array of planned radio telescopes are analyzed, and a method to reduce the interaction between rotating paraboloid antenna and feed is proposed. A broadband feed of square plate is designed. Through the simulation analysis, structure optimization, physical fabrication and performance test of 3D electromagnetic simulation software CST, the results show that in the range of low frequency band 400MHz~1200MHz, The high efficiency of antenna array can also be guaranteed by having very good broadband performance, but in the high frequency band 1200MHz~1400MHz, the matching performance of feed line and square plate broadband feed becomes very poor. For this reason, an improved folding broadband feed is designed. Through simulation analysis, structure optimization, fabrication and performance test, an ideal broadband feed structure is obtained. The measured results show that it has very good broadband performance in the 400MHz~1200MHz band. The echo loss is less than-10 dB, the VSWR (VSWR) is less than 2.5, and the bandwidth is about 50%, which meets the technical requirements of the project. Finally, three groups of 6m aperture element paraboloid antennas are used for experimental study. In order to ensure the ideal wavefront of the paraboloid antenna, the phase center coincides with the focus of the paraboloid antenna in the process of feed installation and adjustment. In the experiment, the system temperature is measured by switching the feed source and the standard noise source, and the system temperature is about 70K. The paraboloid antenna system is used to observe the sun, CygA,Cas A and other radio sources, and a better interference pattern is obtained. The observed data are compared with the simulated data, and the slope of the interference fringes is almost in good agreement with each other. It is shown that the consistency of the broadband feed-paraboloid antenna system is very good. The broadband feed and its experimental scheme proposed in this paper are beneficial to the in-depth study of the feed broadband problem and provide the optimal selection scheme for the broadband feed of the "Natural Sound Plan".
【学位授予单位】：杭州电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P159.4
[Abstract]:The study of dark energy is an important frontier issue in contemporary scientific research. according to modern cosmic theory, the large-scale structure of the universe is accurately measured by means of radio observation. The expansion velocity of the universe at different red shifts can be measured by using the baryons acoustic oscillations in its spatial power spectrum, and the detection of dark energy can be realized. According to the "sounds of Nature Plan" put forward by the National observatory of the Chinese Academy of Sciences, this paper explores a design method of special broadband feed, and develops a new broadband feed which maintains good electrical performance in the range of 400MHz~1400MHz frequency band, which meets the requirements of the plan. Based on the comparative analysis of the research status of antenna array and broadband feed at home and abroad, this paper points out that when the broadband feed is in 225MHz~750MHz band, the symmetry of far-field radiation pattern is poor, the echo loss is large, and the matching is not good. By introducing the working principle of reflector antenna and the theory of electromagnetic field, the special indexes of broadband feed in the array of planned radio telescopes are analyzed, and a method to reduce the interaction between rotating paraboloid antenna and feed is proposed. A broadband feed of square plate is designed. Through the simulation analysis, structure optimization, physical fabrication and performance test of 3D electromagnetic simulation software CST, the results show that in the range of low frequency band 400MHz~1200MHz, The high efficiency of antenna array can also be guaranteed by having very good broadband performance, but in the high frequency band 1200MHz~1400MHz, the matching performance of feed line and square plate broadband feed becomes very poor. For this reason, an improved folding broadband feed is designed. Through simulation analysis, structure optimization, fabrication and performance test, an ideal broadband feed structure is obtained. The measured results show that it has very good broadband performance in the 400MHz~1200MHz band. The echo loss is less than-10 dB, the VSWR (VSWR) is less than 2.5, and the bandwidth is about 50%, which meets the technical requirements of the project. Finally, three groups of 6m aperture element paraboloid antennas are used for experimental study. In order to ensure the ideal wavefront of the paraboloid antenna, the phase center coincides with the focus of the paraboloid antenna in the process of feed installation and adjustment. In the experiment, the system temperature is measured by switching the feed source and the standard noise source, and the system temperature is about 70K. The paraboloid antenna system is used to observe the sun, CygA,Cas A and other radio sources, and a better interference pattern is obtained. The observed data are compared with the simulated data, and the slope of the interference fringes is almost in good agreement with each other. It is shown that the consistency of the broadband feed-paraboloid antenna system is very good. The broadband feed and its experimental scheme proposed in this paper are beneficial to the in-depth study of the feed broadband problem and provide the optimal selection scheme for the broadband feed of the "Natural Sound Plan".
【学位授予单位】：杭州电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P159.4
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