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.