Losses, sidelobes, and cross polarization caused by feed-supportstruts in reflector antennas: design curves

In a symmetrical reflector antenna the feed system and its support struts block the aperture and thereby deteriorate the radiation characteristics. Simple design curves are presented for the efficiency reduction, the sidelobe levels, and the cross polarization caused by strut blockage. The results are obtained from an analytical study that includes the induced field ratio (IFR) of the struts. The most significant IFR values for struts with circular cross section are calculated and plotted in a way which makes them easy to use as design curves. The use of the design curves is demonstrated by an example