Broadband radio interferometer utilizing a sequential triggering techniquefor locating fast-moving electromagnetic sources emitted from lightning

A broadband radio interferometer to investigate the location of fast-moving electromagnetic (EM) sources emitted from lightning discharges has been de signed, A sequential triggering technique was applied to the system for rec ording the data of broadband electromagnetic pulses from 25 to 250 MHz. Onc e the electromagnetic pulse is detected and its amplitude exceeds a thresho ld level, the triggering circuit is turned on to record the waveform and ge t ready to acquire another pulse afterwards. This technique can overcome th e limitation of the digitizer's memory due to such high digitization rate a nd very large bandwidth. We have implemented our system to locate and retra ce fast-moving electromagnetic sources emitted from lightning discharges du ring a held experiment in Australia in summer 1997, As one of the results, a cloud-to-ground lightning discharge has been reconstructed in the two-spa tial dimension and in time sequence.