In this study, the impact of finite ground plane edge diffractions on the amplitude patterns of aperture antennas is examined. The Uniform Theory of Diffraction (UTD) and the Geometrical Optics (GO) methods are utilized to calculate the amplitude patterns of a conical horn, and rectangular and circular waveguide apertures mounted on square and circular finite ground planes. The electric field distribution over the antenna aperture is obtained by a modal method, and then it is employed to calculate the geometrical optics field using the aperture integration method. The UTD is then applied to evaluate the diffraction from the ground planes' edges. Far-zone amplitude patterns in the E and H planes are finally obtained by the vectorial summation of the GO and UTD fields. In this paper, to accurately predict the H-plane amplitude patterns of circular and rectangular apertures mounted on square ground plane, the E-plane edge diffractions need to be included because the E-plane edge diffractions are much more intensive than those of the H-plane edge regular and slope diffractions. Validity of the analysis is established by satisfactory agreement between the predicted and measured data and those simulated by Ansoft's High Frequency Structure Simulator (HFSS). Good agreement is observed for all cases considered.
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