Reduction of radiation from central exciting region of Eleven feed and pattern improvements for VLBI2010 applications

Multiport, decade bandwidth Eleven feed for prime focus reflector is ongoing development for VLBI 2010 applications. Current version of this feed uses four differential lines used to excite the log-periodic arrays above ground plane. These excitation lines packaged in small central region referred as centre puck shows radiation from lines above 10GHz causing distortion in feed pattern. This paper focuses on these radiations from exciting structures and proposes new methods to efficiently excite log-periodic arrays of Eleven feed while minimizing the radiation losses.