暗能量探測專用寬帶饋源研制
發(fā)布時間：2019-05-23 02:45
【摘要】：暗能量研究是當(dāng)代科學(xué)研究中的重大前沿問題，現(xiàn)代宇宙理論認(rèn)為，通過射電觀測手段，對宇宙大尺度結(jié)構(gòu)進(jìn)行精密測量，利用其空間功率譜中的重子聲學(xué)振蕩特征測定不同紅移處宇宙的膨脹速度，，可實(shí)現(xiàn)暗能量的探測。本文依據(jù)中國科學(xué)院國家天文臺所提出的“天籟計(jì)劃”，探索一種專用寬頻帶饋源的設(shè)計(jì)方法，研制在400MHz~1400MHz頻帶范圍內(nèi)均保持良好電性能的新型寬頻帶饋源，滿足天籟計(jì)劃要求。 論文在對比分析國內(nèi)外天線陣及寬頻帶饋源研究現(xiàn)狀基礎(chǔ)上，指出了當(dāng)前寬頻帶饋源在225MHz~750MHz頻段時，遠(yuǎn)場輻射方向圖對稱性較差、回波損耗較大、匹配性不好等缺陷。通過引入反射面天線工作原理和電磁場理論，分析了天籟計(jì)劃射電望遠(yuǎn)鏡陣列中寬頻帶饋源的特殊指標(biāo)，提出減少旋轉(zhuǎn)拋物面天線與饋源相互影響的方法。 設(shè)計(jì)了一款四方板寬頻帶饋源，通過三維電磁仿真軟件CST的仿真分析與結(jié)構(gòu)優(yōu)化、實(shí)物制作和性能測試，結(jié)果表明在低頻段400MHz~1200MHz范圍內(nèi)，具有非常好的寬頻性能也可保證天線陣列的高效率，但在高頻段1200MHz~1400MHz內(nèi)，饋線和四方板寬頻帶饋源匹配性能變得很差。為此，設(shè)計(jì)了改進(jìn)折疊型的寬頻帶饋源，經(jīng)仿真分析、結(jié)構(gòu)優(yōu)化、制作和性能測試，獲得一款理想的寬頻帶饋源結(jié)構(gòu)型式，實(shí)測表明在400MHz~1200MHz頻帶內(nèi)具有非常好的寬頻性能，其回波損耗低于-10dB，電壓駐波比（VSWR）小于2.5，帶寬約為50%，較好地滿足了天籟計(jì)劃項(xiàng)目的技術(shù)要求。 本文最后利用三組6m口徑單元拋物面天線進(jìn)行實(shí)驗(yàn)研究，為保證拋物面天線具有理想的波前，饋源裝調(diào)過程中使相位中心與拋物面天線的焦點(diǎn)重合。實(shí)驗(yàn)中主要通過饋源和標(biāo)準(zhǔn)噪聲源的切換來測定系統(tǒng)溫度，測得系統(tǒng)溫度大約為70K；用拋物面天線系統(tǒng)觀測太陽、CygA、Cas A等射電源，得到了較好的干涉圖樣，將觀測數(shù)據(jù)和模擬數(shù)據(jù)進(jìn)行比較，從干涉條紋的斜率上看兩者幾乎完全吻合，說明寬頻帶饋源——拋物面天線系統(tǒng)的一致性非常好。 本文所提出的寬頻帶饋源及其試驗(yàn)方案，有利于饋源寬頻帶問題的深入研究，為“天籟計(jì)劃”的寬頻帶饋源提供了優(yōu)選方案。
[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".
【學(xué)位授予單位】：杭州電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：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".
【學(xué)位授予單位】：杭州電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：P159.4
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