Radiation characteristics of a spherical helical antenna

Abstract

A helical antenna, consisting of a winding over a spherical surface, is proposed and investigated, both theoretically and experimentally. The winding is such that a constant spacing between turns is maintained. It is fed coaxially, with the inner conductor forming the helical winding and the outer conductor becoming the ground plane. Radiation characteristics of the proposed spherical helix are calculated, using the method of moments, and compared with the measured results. The results of this investigation indicate that radiation properties of the spherical helix are markedly different from those of the conventional cylindrical helix. Of particular interest is that, over a certain bandwidth, the proposed helix is capable of providing circular polarisation over a broad beamwidth. This property and its compact size make the spherical helix attractive to mobile radio communication systems with low channel capacity.