Hard struts reduce aperture blockage in axisymmetric reflector antennas

In axisymmetric reflector antennas the primary feed or the subreflector will most often be supported by struts that block the aperture and thereby cause a reduction of the directivity and an increase of the sidelobe levels. It is desirable to shape and load the struts in such a way that this blockage is minimized. The authors have investigated experimentally how the blockage can be reduced by using hard struts, i.e., struts that are loaded in order to obtain a hard boundary condition for the E-field. The hard boundary condition minimizes the scattering from the strut. The idea is based on the concept of artificially soft and hard surfaces in electromagnetics.<>