Noise reduction of lightning electric fields measurements using filtering in the fractional Fourier domain

Abstract

Lightning electric field measurements are degraded by the presence of noise. In fact, during the measure of lightning electromagnetic pulses (LEMP), the electromagnetic environment and the measuring systems composed by analog-digital converters (ADC), coupling system and electronic circuits, inevitably introduce noise in the measured signals. In recent years, several activities has been developed by EMC-UNC group to measure, study and classify the parameters of lightning electric fields (LEF) in Bogotá, Colombia. However, the obtained measurements are distorted by significant noise levels. This paper shows the results of the first approach to apply the fractional Fourier transform as an alternative technique to reduce the presence of noise in a set of electric field signatures and presents the basic conditions to realize the filtering process in the fractional Fourier domain. Afterwards, some lightning electric field temporal characteristics were analyzed by using the processed signatures. Important differences between the processed and the original waveforms were observed.