时频联合分析在闪电定位中的应用

为了揭示闪电甚高频（very high frequency，VHF）辐射源的时频特性，探索时频分析方法在闪电VHF辐射源定位中的应用，文中利用Wigner-Ville分布（Wigner-Ville distribution，WVD）对闪电宽带VHF辐射信号进行了时频分析，提出一种半二维相关（semi-two-dimensional correlation，STDC）时延算法来实现闪电VHF辐射源的定位，并通过数值模拟和人工引雷观测数据对定位算法进行了验证.时频分析结果揭示了在纳秒尺度上，先导宽带VHF辐射"倾斜状"的时频分布特征中高频辐射先于低频成分到达，典型的倾斜斜率约为-3 MHz/ns.提出的时频定位算法可以计算信号不同频率成分的时延，便于去除干扰点影响.利用本算法对一次人工引雷直窜先导进行了定位分析，通过舍去调频（frequency modulation，FM）干扰，能够清晰描绘先导VHF辐射源的发展过程，定位结果与高速摄像图像吻合，进一步丰富了短基线VHF的定位方式.

Application of time-frequency joint analysis in lightning location

In order to reveal the time-frequency characteristics of lightning VHF radiation sources and explore the application of time-frequency analysis methods in the location of lightning VHF radiation sources, the Wigner-Ville distribution (WVD) is used to analyze the time-frequency characteristics of lightning broadband VHF radiation signals. On this basis, a semi-two-dimensional correlation time delay algorithm is proposed to realize the location of lightning VHF radiation source. Finally, the localization algorithm is verified by numerical simulation and artificial lightning observation data. The results of time-frequency analysis reveal that the time-frequency distribution of broadband VHF radiation is "tilted" at nanosecond scale. The high-frequency radiation arrives before the low-frequency components, and the typical tilt slope is about -3 MHz/ns. The proposed time-frequency localization algorithm can calculate the delay of different frequency components of the signal, and facilitate the removal of the influence of the interference point. This algorithm is used to locate and analyze the dart leader in an artificially triggered lightning. The development process of the VHF radiation source can be clearly depicted by deducting the FM (FM) interference. The mapping result is consistent with the high-speed camera image, which further enriching the positioning of VHF location.