Browsing by Author "Zekarias, Afework"

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    Design of Improved TEM Horn Antenna in Double Exponential Approach for Impulse GPR Applications
    (Addis Ababa University, 2021-05) Zekarias, Afework; Ephrem, Teshale
    Ground Penetrating Radar (GPR) is a popular geophysical technique that is used to investigate the ground using electromagnetic waves. Analogous to medical imaging GPR is used for subsurface imaging and exploration. Antenna is a key element of any GPR system. The design of GPR antennas differs from the classical approach. Classical antennas are designed for operating in free space but antennas for GPR must operate in the vicinity of the ground and this is a major constraint in their design. The GPR antenna must couple the electromagnetic waves directly in to the ground. In this thesis, improved Transverse Electromagnetic (TEM) horn antennas are designed for impulse GPR applications and improving the design of the TEM horn antenna is focused on reducing the aperture reflections in double exponential approach. Student version of FEKO software is used in the simulation and The simulation results show that, TEM horn antennas, TEM60cm and TEM120cm each with aperture impedance of 200 and 250 Ohm designed in double exponential approach have less Voltage Standing Wave Ratio(VSWR) than TEM horn antenna with 377 Ohm aperture impedance of similar size as the frequency of operation increase and the VSWR of TEM60cm and TEM120cm each with aperture impedance of 200 and 250 Ohm is less than 2 over an ultra-wide frequency range within the frequency range of interest.