Reduced sidelobes and cross-polarization of axial mode helix using a soft corrugated ground plane

The authors investigate the use of soft surface, i.e., a corrugated ground plane, to replace the smooth conducting disk of the Kraus helical antenna. It is shown that the sidelobe level and the cross-polarization can be improved compared to using a smooth disk. The same improvements are obtained by only corrugating the outer part of the disk. The return loss is almost identical to that obtained by a smooth conducting disk. The improved helical antenna with a soft corrugated disk is an attractive cheap feed for a primary-fed reflector or dual-reflector antenna. This improved model can also be used as an element in an array. The reduced sidelobe in the ground plane surface direction will also reduce the mutual coupling.<>