Research On The Principle And Performance Parameters Of VHF Lightning Detection Radar

Thunderstorms are one of the most severe meteorological disasters,and the process of thunderstorm is bound to be accompanied by lightning,which often causes the casualties and damage of various facilities and devices.Accordingly,accurate detection of spatial location of lightning attach enormous implication on the study and prediction of thunderstorm and lightning,as well as disaster investigation and loss assessment due to lightning activity.When lightning comes,the electromagnetic radiation of wide spectrum caused by the change of instantaneous strong current make the passive detection of lightning become feasibility.On the other hand,the high temperature ionization effect is contributed to strong current that generates a large number of free electrons,which can reflect effectively electromagnetic wave.That provides sufficient condition to conduct the active(radar)detection of lightning.For the method of passive detection of lightning,the location of lightning can be achieved by probing the direction of the electromagnetic wave generated by lightning.Correspondingly,the error of passive lightning detection based on common method of time-of-arrival is analyzed and simulated.Further,owing to the diversity of lightning(i.e.,the possibility that multiple lightning may occur simultaneously in a certain region),and the reason that a tree-shaped lightning is equivalent to the distribution of multiple sources,the active method depended on radar for detection of lightning is proposed,which may obtain the more accurate results of spatial position.This paper analyzes the frequency band suitable for active detection of lightning and points out the special advantages of VHF band,as well as describes thoroughly the conceptual structure and the principle of operation of the VHF lightning detection radar(i.e.,the multi-pulse integration operational mode based on lightning triggered synchronous detection).On this basis,the phased array working mode based on wide transmission and narrow receive of VHF lightning detection radar is determined,and other main operated parameters of radar,such as transmitting power and the characteristic of transmitting Yagi antenna lobe,etc.,are derived.Further,the narrow beam forming algorithm of receive and performance are discussed.The simulated results demonstrated that under the condition of 60° wide transmitting beam/transmitting antenna gain of 8dBi?3° receive narrow beam/receive antenna gain of 18dBi?1?s transmitting pulse width/distance resolution of 150 m,and taking account into coherent accumulation gain,the detection power of radar canreach 100 km,as well as the cross distance resolution of 20 km is 1km.