Wideband enhancement of coated metallic hard struts by using magnetic materials

There are many situations where the antenna electromagnetic waves are obstructed by some mechanical structures that cause an increase of the sidelobes and gain reduction. The mechanical structure consists often of one or more rods, e.g. feed support struts in axisymmetric reflector antennas and the framework of space frame radomes. Scattering from rods and struts are strongly polarization dependent when the cross-section dimensions are in the order of a wavelength. The present paper represents an attempt to increase the bandwidth of the hard struts that can be realized by coating the metallic surfaces with uniform magnetic or dielectric layer. We consider initially a strut coated with a magnetic or dielectric layer, i.e. no corrugations and no metallic strips on it. This strut coated with a dielectric or magnetic layer will have minimum forward scattering, for the TM-case only. It does not retain its minimum scattering characteristics for the TE-case, for which we need the corrugations or strips. Still such a strut is applicable in a linearly polarized system, to reduce scattering for TM-case blockage losses, e.g. support struts located in the E-plane of axisymmetric reflector antennas.