超短基线电磁脉冲阵在电磁辐射源测向中的应用
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摘要
为提高电磁辐射源的定位精度,该文提出一种利用光纤方式同步的超短基线电磁探测阵列(CASMA)。该阵列包括5个电磁探测站和1个控制中心,阵元间距约为1 km(基线长度与波长的比值约为0.1),同步精度可达10 ns。CASMA用来测量20～70 kHz长波发射电台的垂直电场信号,并利用低频电磁干涉成像算法计算发射电台的方位角。通过实验对比可以发现,估计的发射台方位角与真实发射台方位角之间的误差小于0.2°,远远优于传统的波达角估计方法。因此,CASMA对电磁辐射源具有很高的测向精度。根据实验结果,在2500 km范围内,若两CASMA电磁探测阵对电磁辐射源进行交汇定位,定位精度预期可达0.5%·R(R为探测距离)。
To improve the location resolution of electromagnetic radiation source, a ultra-short baseline network CASMA(Mini-Array by Chinese Academy of Sciences) is proposed for detection, utilizing optical fiber for timing. CASMA contains 5 electromagnetic detection stations and a control unit. The distance between each pair of stations is about 1 km, meaning that the length of baseline to the wavelength is about 0.1. The timing accuracy is about 10 ns. CASMA is applied to record the vertical electric field emitting by radio transmitters.CASMA utilizes interferometric imaging algorithm to calculate the transmitters' azimuth. By experiment, the calculated azimuths approach the expected azimuths with deviations are less than 0.2°, showing many advantages over traditional systems or methods. Consequently, CASMA has accuracy direction finding resolution for electromagnetic radiation source. According to the results, the location accuracy may be expected to be 0.5%·R in a 2500 km scope where R is the distance between the electromagnetic radiation source and CASMA using two sets of CASMA for intersection positioning.
To improve the location resolution of electromagnetic radiation source, a ultra-short baseline network CASMA(Mini-Array by Chinese Academy of Sciences) is proposed for detection, utilizing optical fiber for timing. CASMA contains 5 electromagnetic detection stations and a control unit. The distance between each pair of stations is about 1 km, meaning that the length of baseline to the wavelength is about 0.1. The timing accuracy is about 10 ns. CASMA is applied to record the vertical electric field emitting by radio transmitters.CASMA utilizes interferometric imaging algorithm to calculate the transmitters' azimuth. By experiment, the calculated azimuths approach the expected azimuths with deviations are less than 0.2°, showing many advantages over traditional systems or methods. Consequently, CASMA has accuracy direction finding resolution for electromagnetic radiation source. According to the results, the location accuracy may be expected to be 0.5%·R in a 2500 km scope where R is the distance between the electromagnetic radiation source and CASMA using two sets of CASMA for intersection positioning.
引文
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[18]CARTER G C.Coherence and time delay estimation[J].Proceedings of the IEEE,1987,75(2):236-255.doi:10.1109/PROC.1987.13723.
[2]CUMMER S,LI Jingbo,HAN Feng,et al.Quantification of the troposphere-to-ionosphere charge transfer in a gigantic jet[J].Nature Geoscience,2009,2(9):617-620.doi:10.1038/NGEO607.
[3]FULLEKRUG M,ROUSSELDUPRE R,SYMBALISTY EM D,et al.Relativistic electron beams above thunderclouds[J].Atmospheric Chemistry&Physics&Discussions,2011,11(15):7747-7754.doi:10.5194/acp-11-7747-2011.
[4]GEMELOS E S,INAN U S,WALT M,et al.Seasonal dependence of energetic electron precipitation:Evidence for a global role of lightning[J].Geophysical Research Letters,2009,36(21):147-148.doi:10.1029/2009GL040396.
[5]QIN Jianqi,CELESTIN S,and PASKO V P.Low frequency electromagnetic radiation from sprite streamers[J].Geophysical Research Letters,2012,39(22):1-5.doi:10.1029/2012GL053991.
[6]STOCK M G,AKITA M,RISON W,et al.Continuous broadband digital interferometry of lightning using a generalized cross-correlation algorithm[J].Journal of Geophysical Research Atmospheres,2014,119(6):3134-3165.doi:10.1002/2013JD020217.
[7]THOMAS R J,KREHBIEL P R,RISON W,et al.Accuracy of the lightning mapping array[J].Journal of Geophysical Research Atmospheres,2004,109(D14):1-34.doi:10.1029/2004JD004549.
[8]CUMMINS K L,MURPHY M J,BARDO E A,et al.Acombined TOA/MDF technology upgrade of the U.S.national lightning detection network[J].Journal of Geophysical Research Atmospheres,1998,103(D8):9035-9044.doi:10.1029/98JD00153.
[9]SMITH D A,EACK K B,HARLIN J,et al.The Los Alamos Sferic Array:A research tool for lightning investigations[J].Journal of Geophysical Research Atmospheres,2002,107(D13):5-14.doi:10.1029/2001JD000502.
[10]BITZER P M,CHRISTIAN H J,STEWART M,et al.Characterization and applications of VLF/LF source locations from lightning using the Huntsville Alabama Marx Meter Array[J].Journal of Geophysical Research Atmospheres,2013,118(8):3120-3138.doi:10.1002/jgrd.50271.
[11]MEZENTSEV A and FULLEKRUG M.Mapping the radio sky with an interferometric network of low‐frequency radio receivers[J].Journal of Geophysical Research Atmospheres,2013,118(15):8390-8398.doi:10.1002/jgrd.50671.
[12]FULLEKRUG M,MEZENTSEV A,WATSON R,et al.Array analysis of electromagnetic radiation from radio transmitters for submarine communication[J].Geophysical Research Letters,2014,41(24):9143-9149.doi:10.1002/2014GL062126.
[13]FULLEKRUG M,MEZENTSEV A,WATSON R,et al.Map of low frequency electromagnetic noise in the sky[J].Geophysical Research Letters,2015,42(11):4648-4653.doi:10.1002/2015GL064142.
[14]FULLEKRUG M,SMITH N,MEZENTSEV A,et al.Multipath propagation of low frequency radio waves inferred from high resolution array analysis[J].Radio Science,2015,50(11):1141-1149.doi:10.1002/2015RS005781.
[15]LIU Zhongjian,KUANG L K,MEZENTSEV A,et al.Variable phase propagation velocity for long-range lightning location system[J].Radio Science,2016,51(11):1806-1815.doi:10.1002/2016RS006058.
[16]FULLEKRUG M,LIU Zhongjian,KOH K,et al.Mapping lightning in the sky with a mini array[J].Geophysical Research Letters,2016,43(19):10448-10454.doi:10.1002/2016GL070737.
[17]LYU Fanchao,CUMMER S A,SOLANKI R,et al.A low‐frequency near‐field interferometric TOA 3D Lightning Mapping Array[J].Geophysical Research Letters,2014,41(22):7777-7784.doi:10.1002/2014GL061963.
[18]CARTER G C.Coherence and time delay estimation[J].Proceedings of the IEEE,1987,75(2):236-255.doi:10.1109/PROC.1987.13723.