Simulations of the Antenna-shielding Effect of the Daocheng Solar Radio Telescope (DSRT)
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摘要: 稻城太阳射电望远镜(DSRT)由313面6 m直径抛物面天线组成。天线接收信号幅值和相位的精确修正是决定DSRT成像质量的关键因素。然而DSRT阵列可能会出现邻近天线相互遮挡的问题,从而改变接收信号的幅值和相位,影响其成像质量。利用电磁仿真软件计算了接收频率为300 MHz(波长λ=1 m)时的相邻两单元与相邻三单元两种情况。三元系统中遮挡效应的影响仅比双元系统中相关影响略为显著。在本文考虑的最严重的遮挡情况(天线边缘的投影间距D = –1λ)下,对于双/三元系统,相对于单天线系统水平和垂直增益分别降低了0.6/0.6 dB和 0.3/0.4 dB,相位偏差分别为–3.3º/–3.871º和–1.744º/–2.244º。此外还分析了其他遮挡情况。研究表明DSRT系统中的天线遮挡效应分析可由双元系统充分描述,在后期数据处理时应适当考虑该效应,尽量提升DSRT数据的利用效率和成图质量。Abstract: The Daocheng Solar Radio Telescope (DSRT) is a next-generation solar radio telescope funded by the Chinese Meridian Project–Phase II. DSRT is composed of 313 parabolic antennas with a diameter of six meters. The antennas are evenly distributed in a circle with a diameter of one kilometer. With the synthetic aperture imaging techniques, key factors determining the DSRT imaging quality are accurate calibrations of amplitude and phase of the received signals. Yet, under some circumstances, adjacent antennas of DSRT may shield each other, which will affects the amplitude and phase of the received signals and thus deteriorate imaging quality. In this study, such shielding effects of three- or two-antenna using the electromagnetic simulation software at frequencies of 300 MHz (λ=1 m) were simulated. The shielding effect in the three-antenna system is slightly worse than that in the two-antenna system. When the projected distance of adjacent antennas is taken to be –1λ, i.e., the most serious effect of shielding considered here, the horizontal and vertical gains of the system with two/three antennas decline by 0.6/0.6 dB and 0.3/0.4 dB, respectively, and the horizontal and vertical phase deviations are –3.3º/–3.871º and –1.744º/–2.244º, respectively, compared to the system with one antenna. Other situations with different projected shielding distances are also investigated. The results show that the two-antenna system can sufficiently describe the shielding effect associated with DSRT. Such effect should be properly taken into account when processing the future DSRT data so as to improve the data usage efficiency and imaging quality.
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表 1 双/三元系统中不同遮挡情况水平极化接收天线的辐射性能比较
Table 1. Comparison of radiation characteristics of horizontal polarized antennas under different shielding conditions in the two/three-antenna system
双/三元系统主方向增益/dBi 双/三元系统旁瓣水平/dB 双/三元系统主波束指向/(°) 单天线 23.8/23.8 19.0/19.0 0/0 D=1λ 23.8 /23.8 19.2/19.1 0/0 D=0.5λ 23.8/23.8 19.9/19.4 0/0.5 D=0λ 23.8/23.8 19.8/19.0 0.5/0.5 D=–0.5λ 23.6/23.6 17.0/18.7 1.0/1.0 D=–1λ 23.2/23.2 17.7/16.2 1.5/1.5 表 2 双/三元系统中不同遮挡情况垂直极化接收天线的辐射性能比较
Table 2. Comparison of radiation characteristics of vertical polarization under different shielding conditions in the system with two/three-antenna system
双/三元系统主方向增益/dBi 双/三元系统旁瓣水平/dB 双/三元系统主波束指向/(°) 单天线 23.8/23.8 19.0/19.0 0/0 D=1λ 23.8/23.8 19.1/19.1 0/0 D=0.5λ 23.8/23.8 19.4/19.4 0/0.5 D=0λ 23.8/23.8 19.0/19.0 0.5/0.5 D=–0.5λ 23.6/23.7 17.9/18.7 1.0/1.0 D=–1λ 23.5/23.4 15.6/16.2 1.5/1.5 表 3 双/三元系统中不同间距遮挡下接收天线的主方向相位比较
Table 3. Comparison of radiation phase along the main direction of the receiving antenna under different shielding distance in the two/three-antenna system
主方向相位变化 双/三元系统水平极化/(°) 双/三元系统垂直极化/(°) 单天线 0/0 0/0 D=1λ –0.279/–0.309 –0.079/–0.093 D=0.5λ –0.767/–0.819 –0.089/–0.137 D=0λ –1.289/–1.545 –0.393/–0.490 D=–0.5λ –1.983/–2.096 –1.085/–0.490 D=–1λ –3.300/–3.871 –1.744/–2.244 -
[1] MCLEAN D J. Metre-wave solar radio bursts[M]//Solar Radiophysics. Cambridge: Cambridge University Press, 1985 [2] WILD J P, SMERD S F, WEISS A A. Solar bursts[J]. Annual Review of Astronomy and Astrophysics, 1963, 1: 291-366 doi: 10.1146/annurev.aa.01.090163.001451 [3] FENG S W, CHEN Y, KONG X L, et al. Radio signatures of coronal-mass-ejection-streamer interaction and source diagnostics of type II Radio Burst[J]. The Astrophysical Journal, 2012, 753(1): 21 doi: 10.1088/0004-637X/753/1/21 [4] CHEN Y, DU G H, FENG L, et al. A solar type II radio burst from coronal mass ejection-coronal ray interaction: simultaneous radio and extreme ultraviolet imaging[J]. The Astrophysical Journal, 2014, 787(1): 59 doi: 10.1088/0004-637X/787/1/59 [5] FENG S W, CHEN Y, KONG X L, et al. Diagnostics on the source properties of a type II radio burst with spectral bumps[J]. The Astrophysical Journal, 2013, 767(1): 29 doi: 10.1088/0004-637X/767/1/29 [6] ALAIN K, JEANMARC D. The nancay radioheliograph[J]. Coronal Physics from Radio and Space Observations, 1997, 483: 192-201 [7] GRECHNEV V V, LESOVOI S V, SMOLKOV G Y, et al. The Siberian solar radio telescope: the current state of the instrument, observations, and data[J]. Solar Physics, 2003, 216(1/2): 239-272 doi: 10.1023/A:1026153410061 [8] XU L, YAN Y H, MA L, et al. Image processing for synthesis imaging of Mingantu Spectral Radioheliograph (MUSER)[J]. Multimedia Tools and Applications, 2018, 77(16): 20937-20954 doi: 10.1007/s11042-017-5545-5 [9] NAKAJIMA H, NISHIO M, ENOME S, et al. The Nobeyama radioheliograph[J]. Proceedings of the IEEE, 1994, 82(5): 705-713 doi: 10.1109/5.284737 [10] 杜清府, 程仁君, 陈昌硕, 等. 太阳射电观测系统多通道变频电路一致性补偿方法与实现[J]. 中国科学:技术科学, 2019, 49(8): 901-909 doi: 10.1360/N092018-00408DU Qingfu, CHENG Renjun, CHEN Changshuo, et al. A compensation method for the consistency of multi-channel mixing circuit for solar radio observation system[J]. Scientia Sinica Technologica, 2019, 49(8): 901-909 doi: 10.1360/N092018-00408 [11] 徐珂, 尚自乾, 严发宝, 等. 毫米波宽带太阳射电观测系统的信号平坦度补偿方法[J]. 中国科学:技术科学, 2021, 51(1): 413-423XU Ke, SHANG Ziqian, YAN Fabao, et al. Compensation method of signal flatness for a broadband solar millimeter radio observation system[J]. Scientia Sinica Technologica, 2021, 51(1): 413-423 [12] THOMPSON A R, MORAN J M, SWENSON JR G W. Interferometry and Synthesis in Radio Astronomy[M]. New York: John Wiley & Sons, 2008 [13] ROHLFS K, WILSON T L. 射电天文工具[M]. 姜碧沩, 译. 北京: 北京师范大学出版社, 2008ROHLFS K, WILSON T L. Tools of Radio Astronomy[M]. JIANG Biwei, trans. Beijing: Beijing Normal University Press, 2008 [14] 颜毅华, 陈林杰, 谭宝林, 等. 太阳大气等离子体动力学射电成像探测系统[J]. 中国科学:物理学 力学 天文学, 2019, 49(5): 059608YAN Yihua, CHEN Linjie, TAN Baolin, et al. Radioheliograph array for the solar atmospheric dynamics[J]. Scientia Sinica Physica, Mechanica & Astronomica, 2019, 49(5): 059608 [15] SERGEY L, ALEXANDER A, ALEKSEY K, et al. Siberian Radioheliograph: first results[J]. Solar-Terrestrial Physics, 2017, 3(1): 3-18 doi: 10.12737/article_58f96ec60fec52.86165286 [16] WANG C. Development of the Chinese meridian project[J]. Chinese Journal of Space Science, 2010, 30(4): 382-384 [17] WANG C. Recent advances in observation and research of the Chinese Meridian Project[J]. Chinese Journal of Space Science, 2018, 38(5): 640-649 [18] 王添鸽, 马迁, 欧刚强. 舰艇卫星通信天线遮挡问题研究[J]. 舰船电子工程, 2019, 39(6): 76-78WANG Tiange, MA Qian, OU Gangqiang. Research on blocking problems of the satellite antenna of warships[J]. Ship Electronic Engineering, 2019, 39(6): 76-78 [19] 王国民, 谷晓鹏, 邱恺. 机载天线遮挡角在地空通信中的影响探析[J]. 通信技术, 2016, 49(12): 1724-1727WANG Guomin, GU Xiaopeng, QIU kai. Effects of airborne-antenna blocking angle on air-grounding communication[J]. Communications Technology, 2016, 49(12): 1724-1727 [20] FENG S W, CHEN Y, LI C Y, et al. Harmonics of solar radio spikes at metric wavelengths[J]. Solar Physics, 2018, 293(3): 39 doi: 10.1007/s11207-018-1263-z [21] STUTZMAN W L, THIELE G A. Antenna Theory and Design[M]. 2 nd ed. New York: Wiley, 1998 [22] 宋东安, 易学勤, 温定娥. 金属挡板遮挡效应试验[J]. 舰船科学技术, 2010, 32(9): 76-79SONG Dong’an, YI Xueqin, WEN Dinge. Experimental study of shaded effectiveness of plates[J]. Ship Science and TEchnology, 2010, 32(9): 76-79