Denoising of lightning electric field signals using fractional Fourier transform

In recent years, several activities have been carried out by EMC-UNC (research group) to measure, study and classify the parameters of lightning electric fields signals in Bogotá, Colombia. However, measurements are distorted and exhibit significant noise levels caused by undesired signals from the electromagnetic environment together with other types of disturbances produced by the measuring system, which inevitably introduces noise in signal measurements. This paper shows the results of applying the fractional Fourier transform (FRFT) as an alternative technique to reduce the presence of noise and also of undesired signal components within a set of electric field signatures. Basic conditions to carry out the filtering process in the fractional Fourier domain (FRFd) are presented. Afterwards, some lightning electric field temporal characteristics are analyzed by using the processed signatures. Important differences between processed and measured waveforms are observed.