Beamwidth Reduction of Helical Antenna Using Single Layer FSS Structure

In this paper, a 3 X 3 frequency selective surface (FSS) structure consisting of Jerusalem cross-shaped unit cell has been designed to use it as a superstrate above the helical antenna to mitigate the beamwidth of the main beam of the helical antenna. The designed helix is a wideband right hand circularly polarized antenna with 10 number of turns operating in axial mode. The FSS is placed at a distance of 19 mm above the helix. The main radiated beam of the helix possesses a beamwidth of 40 degree which constricts to 26 degrees after placing the FSS. The composite structure is operating at 7.93 GHz where a narrower main beam and a satisfactory gain of 12.42 dB can be achieved sustaining the circular polarization. Due to this property, we can use this composite structure as a filter to select a particular frequency (In this paper, it's 7.93 GHz) from a wide 10 dB bandwidth of the helix where we can obtain a circularly polarized radiation pattern with a relatively high Co-Polarization gain and a much narrower main beam.