Electromagnetic scattering from a monopole antenna in the presence of a hemisphere conductor

The wire antenna in the presence of a sphere was studied by Buller and Keshavamurthy (1980), where the integro-differential equation method and the numerical dyadic Green´s function method were used to analyze the input impedance and the radiation pattern of the wire antenna. Good results were obtained which are useful to EMC engineers. In this paper, the radar cross section (RCS) of the grounded antenna/hemisphere structure is calculated by means of mode matching method (MMM) as well as the method of moments (MoM). The former is used to calculate the hemisphere´s scattered fields whereas the latter is used to determine the probe´s induced current. Using image theory, the ground plane is removed and the equivalent sphere and dipole an now illuminated by a pair of plane waves. The fields radiated from the dipole´s induced current is found using the Green´s function technique, taking the influence of the sphere into account. On the other hand, the fields scattered directly by the sphere is easily obtained using the MMM. Then, the total scattered fields of this structure are the vector sum of the scattered fields obtained above. To verity the program, the special case of a/spl rarr/0 was checked and the result agreed very well with that available in the literature. Finally, the effects of the radius a of the hemisphere, the antenna/hemisphere spacing b, and the antenna´s impedance loading Z/sub l/ on the RCS are studied.