'Soft' exterior surface modification for circularly polarized and polarization selective linear array antennas

Linear and planar arrays of radiating apertures, whether fed from waveguide, cavities, stripline, microstrip or in some other way, present a particular problem for circularly polarized or polarization selective antenna designs. This is because the plane conducting ground plane into which the apertures are normally inserted for arrays of this type, is not itself dual polarized owing to the differing field boundary conditions which apply to the E and H components of the radiated electromagnetic wave. This paper describes a ground plane modification which achieves good E/H boundary condition equivalence for a waveguide fed polarization selective linear slot array.