An antenna includes a planar ground plane, a planar exciter, and a plurality of passive elements. The planar ground plane and the planar exciter are disposed orthogonal to a longitudinal axis of the antenna. The planar exciter is spaced apart from the ground plane. The planar exciter is configured to excite right-hand circularly-polarized electromagnetic radiation. The planar exciter is configured to excite first currents orthogonal to the longitudinal axis and substantially no current parallel to the longitudinal axis. The plurality of passive elements is symmetrically disposed azimuthally about the longitudinal axis and spaced apart from the planar exciter. The plurality of passive elements is electromagnetically coupled to the planar exciter. The plurality of passive elements is configured to excite second currents parallel to the longitudinal axis and third currents orthogonal to the longitudinal axis.