Sidelobe reduction of a parabolic reflector with auxiliary reflectors

Reducing the sidelobe level of a reflector antenna in a particular direction is desirable in many applications. A simple way of achieving this reduction is to add auxiliary reflectors either internally over the main reflector surface or externally outside the main reflector surface. Design curves are presented on the size of these auxiliary reflectors versus feed taper and
F/D
to achieve a prescribed sidelobe reduction. Typically, for a 10 dB sidelobe reduction, the diameter of the auxiliary reflector is about a third of the main reflector diameter (10 percent in surface area).