Evaluation of air-gap stacked capacitive antennas for lightning remote sensing

Abstract

This paper evaluates the capacitive antenna performance (sensitivity and frequency shifting) as a lightning sensor in different antenna design structures. Two experiments were carried out, Experiment A - using two different structure antennas, an A3 size capacitive antenna and a quarter A4- sized capacitive antenna, capturing the electric field (E-field) generated by the small spark at a distance of 1 meter away from both antennas. The results were taken in a ratio form of the 1st pulse amplitude captured by quarter A4 size antenna verses 1st pulse amplitude of the waveform captured by A3 antenna for each corresponding spark. Same set up and measurement were taken during the Experiment B except for the quarter A4 size antenna was now being slotted with 6 copper plates were slotted within the gap between the top plate and bottom plate. The result from Experiment A showed an average ratio at 0.1957 with a range of 0.0333 to 0.3085 while the results of Experiment B showed the average value laid at 0.2606 within the range of 0.1581 to 0.4510. The comparison results of Experiment A with Experiment B gave an increment of the sensitivity of the quarter A4 antenna from no stack to fully stacked antenna. However, there was also a significant frequency shifting of the quarter A4 antenna with the change of antenna structure (15% for quarter A4 capacitive antenna without stack; 20% for quarter A4 stacked capacitive antenna).