Sub-wavelength Radio Array Instrumentation and Analysis for Transmitter and Thunderstorm-related Signals

Abstract

This thesis describes the development of new instrumentation and techniques for measuring and analysing radio signals from terrestrial transmitters and atmospheric electrical discharges. The goal was to advance the study of radio interferometry applied to terrestrial sources, particularly by using receiver arrays with sub-wavelength baselines to explore the limits of how small a baseline can reliably detect phase differences in a plane wavefront measured at different array stations. Single sensor recordings of distant atmospheric discharge processes were analysed first to investigate the characteristics of exceptional lightning flashes, and the transient luminous events (optical phenomena associated with atmospheric electrical discharges) caused by them. This was done by comparing the optical appearance of transient luminous events captured by video, with the radio signals received from the causative lightning, showing a relationship between the size of the charge moment change and the morphology of the optical appearance of transient luminous events. Small, field-deployable radio receivers, portable as briefcase sized packages when stowed, and operating at 0-400 kHz, were developed. Arrays of these receivers were deployed with short baselines, from a few metres to several tens of metres, to test phase stability when measuring close, powerful constant transmitter signals at wavelengths or 1500 m, or thirty times as long as the baseline. Finally, arrays of sensors were deployed to a lightning rich environment in Northern Colombia, where successful azimuthal direction-finding was performed on lightning signals with sub-wavelength scale baselines, with the array baseline of around 600 m roughly equivalent to the upper limit of the receivers.

Date of Award	21 Feb 2024
Original language	English
Awarding Institution	University of Bath
Sponsors	Horizon 2020
Supervisor	Martin Fullekrug (Supervisor) & Biagio Forte (Supervisor)