An Improved Method for Analyzing Broadband VHF Interferometer Lightning Observations
An Improved Method for Analyzing Broadband VHF Interferometer Lightning Observations
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DOI：
10.1109/tgrs.2023.3299368
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发表时间：
2023
影响因子：
8.2
通讯作者：
Xiangpeng Fan;P. Krehbiel;M. Stanley;W. Rison;H. Edens;Yijun Zhang
中科院分区：
文献类型：
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作者：
Xiangpeng Fan;P. Krehbiel;M. Stanley;W. Rison;H. Edens;Yijun Zhang
以干涉仪（INTF）天线探测到的甚高频（VHF）脉冲信号为参考单位，提出了一种基于脉冲匹配和峰值提取的闪电定位方法。该方法的第一个关键步骤是通过使用系综经验模式分解（EEMD）方法来优化INTF的原始VHF数据，以通过带通滤波来控制原始信号的质量，从而仅保留40-80 MHz的相对高频分量。然后，通过主窗和辅窗的组合，利用广义互相关实现了不同天线波形的匹配。在微尺度窗口（11 ns），脉冲信号进一步精确匹配，并在阈值和相似性约束下计算到达时间差。最后，采用非线性最小二乘法获得匹配脉冲辐射源的二维坐标。与传统的质心法相比，该方法得到的辐射源数目大大增加。对于不同放电强度的闪电情况，定位辐射源的数量可以增加10-20倍，对于特定的短持续时间和快速变化的放电过程（如飞镖领导者和K事件），定位辐射源的数量可以增加近100倍。在20-88 MHz频率范围内，采样频率为180 MHz时，闪电放电过程的分析分辨率可提高到10 ns。当辐射源被完全定位时，闪电通道的宽度可以成功地从代表空间中定位的辐射源的无尺寸点的密度重建。
Based on the very-high-frequency (VHF) pulse signal detected by interferometer (INTF) antennas as the reference unit, a lightning location method based on pulse matching and peak extraction is proposed in this article. The first key step of this method is to optimize the raw VHF data of the INTF by using the ensemble empirical mode decomposition (EEMD) method to control the quality of the original signal by bandpass filtering to preserve only the relatively high-frequency components of 40–80 MHz. Then, through a combination of main and auxiliary windows, the matching of waveforms from different antennas is realized by means of generalized cross correlation. In a microscale window (11 ns), the pulse signals are further accurately matched, and the arrival time difference is calculated under threshold and similarity constraints. Finally, the 2-D coordinates of the matched pulsed radiation sources are obtained using the nonlinear least-squares method. Compared with the results of the traditional “centroid” approach, the number of radiation sources obtained with the proposed method is greatly increased. For lightning cases with different discharge intensities, the number of located radiation sources can be increased by a factor of 10–20, and for specific short-duration and rapidly changing discharge processes (such as dart leaders and K events), the number of located radiation sources can be increased by a factor of nearly 100. For INTF operation at 20–88 MHz with a sampling rate of 180 MHz, the analytical resolution of the lightning discharge process can be improved to 10 ns. When the radiation sources are fully located, the widths of the lightning channels can be successfully reconstructed from the density of no-size points representing the located radiation sources in space.