Reduction of sidelobe level by improved strut design for low F/D Cassegrain antennas

To reduce sidelobe level caused by strut radiation, an improved design of subreflector support struts, similar to that used in flat reflectors and useful for deep reflectors (F/D of about 0.25) is proposed. Pattern measurements are performed on an open-site antenna test range in the far-field using a 3-m diameter Cassegrain antenna fed by a corrugated horn. Results of comparative measurements that are made for the radiation patterns associated with different support strut configurations are presented. The sidelobe specification of 32-25 log theta is depicted for comparison. The optimum strut design is found to consist of a curved parabolic-shaped supporting strut and a scattering surface structure attached to it on the main reflector facing side.