Polarisation Properties of Electrically Small Antennas on High Impedance Surfaces

An investigation into the effects on the axial ratio of a circularly polarised patch antenna placed on a Sievenpiper type high impedance surface (HIS) is presented. This paper highlights a phenomenon observed in the axial ratio and gain of a circularly polarised antenna when its ground plane is a high impedance surface; the angular position of the antenna on the high impedance surface is critical to its performance, it must therefore be chosen with care and this paper addresses that issue. The aperture of the antenna is placed in the same plane as the top surface of the high impedance surface and the axial ratio is shown to be a function of the antenna´s angular position on the high impedance surface.