Kamal, Syed Osama; (2025) Towards the Beam Scanning Ground Penetrating Radar: Antennas, RF Circuits and Data Processing. Doctoral thesis (Ph.D), UCL (University College London).

Text PhD_Thesis.pdf - Accepted Version Access restricted to UCL open access staff until 1 March 2026. Download (31MB)

Abstract

Ground-penetrating radar (GPR) is a non-invasive geophysical method used to image and map subsurface features by transmitting high-frequency electromagnetic waves into the ground. As these waves encounter different materials with varying electrical properties, some of the energy is reflected back to the surface, where it is detected by a receiver. By analyzing the time and strength of these reflected signals, GPR can provide detailed information about the subsurface structures, such as soil layers, rocks, voids, and buried objects. Borehole ground-penetrating radar extends the capabilities of traditional GPR by utilizing probes inserted into boreholes drilled into the ground. This technique is particularly valuable for subsurface investigations where surface-based GPR is limited by depth or resolution. Borehole GPR allows for more precise imaging of deep subsurface features, including the detection of water content, fractures, and other geological structures. The thesis presents significant contributions to the design and development of components for GPR and borehole GPR systems, aiming to improve subsurface water content measurement using a beam-scanning technique. Two novel designs of X-band coaxial periodic leaky wave antenna arrays are introduced for confined space applications. The first design, a parallel configuration, achieves high gain and narrow beam patterns, making it suitable for cross-borehole radar. The second, an adjacent configuration, offers a more compact design with superior sidelobe and backlobe suppression, enhancing performance in restricted environments. The thesis also introduces two novel impedancetransforming baluns using tandem couplers designed to improve impedance matching for Lband power RF amplifiers. These baluns not only demonstrate relaxed coupling factors and efficient impedance transformation but also have practical applications that have been verified through simulations and practical measurements. These baluns improve impedance matching and efficiency, achieving significant enhancements in performance metrics such as gain, output power, and efficiency of a power amplifier designed to compensate for the losses caused by lowefficiency borehole antennas. The components, specifically designed for L-band SFCW radar or VNA-based measurement, are integral to the beam-scanning borehole geophysical radar for subsurface imaging and contribute to the overall system functionality and performance.

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