Design And Implementation Of Digital Signal Processing Methods Based On VLF/LF Lightning Detection

Lightning is the instantaneous discharge process occurred in the natural atmosphere,including cloud-to-cloud flash and cloud-to-ground flash, which can cause serious naturaldisasters; The Lightning discharge process can produce electromagnetic radiation withfrequency from very low frequency (VLF) to ultra high frequency (UHF).The cloud-to-ground flash is the discharge process which occurs between the cloudsand the ground. It’s peak current can reach tens of thousands to hundreds of thousands ofamps, making a great threat of ground objects. Very low frequency/Low frequency (VLF/LF) pulses associated with the Ground lightning can be treated as the flash monitoringpositioning conditions.Based on cloud to ground flash detection and location in VLF, this paper mainly talkabout the digital signal processing methods from the theory, design to implementationprocess.With regard to the VLF/LF receiving system that composed of orthogonal ring andmonopole antenna, the analog signal filtering is susceptible to interference and residualouter frequency components. Therefore it is need to do band pass filtering with the linearphase FIR filter after analog to digital conversion, and decimate in order to reduce thesubsequent digital calculation and processing requirements. Because the analog front-endprocessing could not be exactly the same, it must be calibrate the channel amplitudeinconsistency to ensure a certain direction finding precision requirements. In fact, largeamounts of data about real-time receiving treatment must consider short-time energydetection, only when detected the data block which contains lightning pulse signal tomake the azimuth angle calculation and upload data, in order to improve the treatmentefficiency of the system. To the effective data block detected, the specific direction findingcalculation way azimuth estimation, eventually obtaining incident signal source DOA ofestimated results.