RADIATION OF AN APERTURE ANTENNA COVERED BY A SPHERICAL-SHELL CHIRAL RADOME AND FED BY A CIRCULAR WAVE-GUIDE

This paper presents a full-wave analysis of the radiation characterist ics of an aperture antenna that is flush-mounted on a ground plane and fed by a circular waveguide supporting the dominant TE11 mode. The an tenna is covered by a dielectric hemispherical chiral radome. Huygen's equivalence principle and the image theory are utilized to simplify t he problem, The magnetic dyadic Green's function for the three-layered geometry is formulated and applied to analyze the radiated electromag netic fields outside the chiral radome. Both the exact and approximate expressions of electric fields valid for the Fresnel and Fraunhofer z ones are obtained using the spherical vector nave functions and their approximations in the far zone. Various chiral materials are assumed a nd computations of antenna parameters are carried out. The effects of the dielectric chiral radome on the radiation power patterns, sidelobe levels, and 3-dB beamwidths are also discussed numerically.