A Low-Profile EBG Structure-Loaded Hat Feed for Suppressing Sidelobe Level of Reflector Antennas

Abstract

A hat feed loaded with low-profile electromagnetic band gap (EBG) structure is proposed to reduce the radiation side lobe levels (SLLs) of reflector antennas. A mushroom shaped EBG structure is designed to suppress the surface currents along the external wall of the feeding waveguide distorting the primary radiation and elevating the SLLs of the reflector antenna. For a 1.2 m X-band hat-fed reflector antenna, it is found that the fluctuations of SLLs with working frequency are suppressed by loading the EBG structures. The study shows that the SLL is reduced by 4.6 dB compared with that of the non-loaded hat feed reflector antenna. The reason for significant SLL reduction in the EBG structure-loaded hat feed reflector antenna is explained, and the prototype is manufactured and tested. The measurement shows that within 7.0 ~ 8.2 GHz, the SLL is lower than −19.4 dB, and the antenna efficiency is over 66.3%. The result proves the superiority of the EBG structure-loaded hat feed reflector antenna over the traditional designs.

Keywords

• Hat feed
• small-aperture reflector antenna
• low sidelobe
• EBG structure