An active receiving antenna for borehole pulsed radar applications

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dc.contributor.advisor Palmer, K. D. en_ZA Van Wyk, M. D. en_ZA
dc.contributor.other University of Stellenbosch. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. 2010-01-07T09:40:27Z en_ZA 2010-06-01T08:51:09Z 2010-01-07T09:40:27Z en_ZA 2010-06-01T08:51:09Z 2002-12 en_ZA
dc.description Thesis (MEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2002. en_ZA
dc.description.abstract An efficient radiating strucllire was needed for borehole pulsed radar applications in the 10-100 MHz frequency band. Both resistively loaded and insulated wire antennas were investigated and an active antenna is proposed as a fmal solution. The study proceeded from the characterization of the origin of radiation on a conductive dipole wire antenna when excited with a transient. Different radiation mechanisms were identified when the antenna was excited with a current or voltage source. The wire antenna in insulated surroundings was modelled using transmission line theory to simulate the antenna in the borehole environment. The transmission line model proved to be useful for investigating conducting and resistively loaded antennas for the dimensions associated with borehole surveys. From the modelling results, it became apparent that the asymmetric resistively loaded antenna might provide the best practical solution. This antenna displays reasonably stable input impedance and low far-field variations for different theta angles across the desired frequency band. Different percentage Wu-King resistive profiles were studied to show that a 50% reduction in the normal Wu-King resistor values will add only a little ringing but have better amplitude response than the 100% Wu-King loading. The asymmetric resistively loaded antenna has better sensitivity to receiving transients when combined with a high impedance source load than when symmetrically loading the antenna. An active antenna incorporating the asymmetric resistively loaded antenna and a low noise current feedback front end amplifier was built and measured in an air environment. The results show that the active antenna has a flat transfer function and reacts as a wide band electric field probe with better resolution than in the conventional 50 Q loaded case en_ZA
dc.language.iso en en_ZA
dc.publisher Stellenbosch : University of Stellenbosch
dc.subject Ground penetrating radar en_ZA
dc.subject Radar -- Antennas en_ZA
dc.subject Dissertations -- Electronic engineering en_ZA
dc.subject Theses -- Electronic engineering en_ZA
dc.subject.other Electrical and Electronic Engineering en_ZA
dc.title An active receiving antenna for borehole pulsed radar applications en_ZA
dc.type Thesis en_ZA
dc.rights.holder University of Stellenbosch
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