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

Abstract

A broadband radio interferometer to investigate the location of fast-moving electromagnetic (EM) sources emitted from lightning discharges has been designed. A sequential triggering technique was applied to the system for recording the data of broadband electromagnetic pulses from 25 to 250 MHz. Once the electromagnetic pulse is detected and its amplitude exceeds a threshold level, the triggering circuit is turned on to record the waveform and get ready to acquire another pulse afterwards. This technique can overcome the limitation of the digitizer's memory due to such high digitization rate and very large bandwidth. We have implemented our system to locate and retrace fast-moving electromagnetic sources emitted from lightning discharges during a field experiment in Australia in summer 1997. As one of the results, a cloud-to-ground lightning discharge has been reconstructed in the two-spatial dimension and in time sequence.

Broadband VHF sources locating system using arrival-time differences for mapping of lightning discharge process

“…After recording the signal, the digital oscilloscope will switch to the trigger-waiting status waiting for the next signal with a 50 ms dead time between successive segments. The utilizing of this function has also been reported by Mardiana and Kawasaki (2000). The oscilloscope is controlled by a personal computer via a GPIB bus.…”

“…Recently, the method of broadband interferometer has been introduced and illustrated (Shao et al, 1996;Mardiana and Kawasaki, 2000;Mardiana et al, 2002). The analysis of this technique is conducted on frequency domain by applying the Fourier transform to the signal.…”

Simulation of Lightning Flash in Time of Arrival (TOA) Method by Using Three Broadband Antennas

“…To solve this equation, parameter "t" needs to be determined in (7). Equations (2) to (6) show while antenna sensor two is sensing a portion of the electromagnetic waveform of a lightning event generated by point "P", the antenna sensor one is sensing another portion of the electromagnetic waveform which is generated in a little far point "P 1 ".…”

“…An implementation of the single station system is by using a short baseline sensor configuration for the purpose of lightning location [4][5][6][7]. This short baseline configuration uses three broadband antennas to identify the azimuth and elevation of lightning source.…”

Simulation of Lightning Flash and Detection Using Time of Arrival Method Based on Four Broadband Antennas

“…A fourth antenna, located as a certain distance away depending on the measuring limitation, can be added to provide the information needed to determine the exact coordinate (X,Y,Z) of the signal source. This TOA technique is usually used for the purpose of lightning location in a small region (10 to 15 km radius) [4][5][6][7].…”