Central-fed hemispherical helical antenna
The characteristics of a hemispherical helical antenna with central-fed are investigated by experiment. Results for a 3-turn hemispherical helix indicate that circular polarization can be obtained over a wide angular range with relatively high gain of about 8 dB. The frequency bandwidth for a 3-dB axial ratio criterion is /spl sim/11%, with a nearly resistive input impedance of 163 /spl Omega/.
Multifilar hemispherical helical antennas
This investigation examines the radiation characteristics of a new bifilar hemispherical helical antenna. Directivity, E- and H-plane radiation patterns, axial ratio and input impedance of a few example designs are calculated. It is shown that the bifilar hemispherical helix provides a nearly constant gain over the measured bandwidth of about 14% and generally elliptical polarization with near circular polarization in limited cases.
Solutions to spherical anisotropic antennas
The antenna as an anisotropic boundary value problem was first considered by Cheo, Rumsey and Welch[1] in their solution to the frequency independent antenna problem. The theoretical results so obtained not only displayed the expected nature of an equiangular spiral antenna, but also closely agreed with actual experimental measurements. Therefore, the directionally conductive surface as a mathematical model of radiator is indeed a potentially powerful approach to antenna analysis. The present paper is a theoretical investigation of the solutions of a class of spherical spiral antennas.