What is "torus reflector antenna"

Hi,
do you know what does "torus reflector antenna" mean? I can not find regular information.

Thank!

It is a reflector type antenna which is formed by rotating a generating curve, having an axis of beam direction, about a fixed axis such that the axis of beam direction defines a beam scanning surface corresponding to the surface of a cone. Scanning is obtained by rotating a feed on the arc of a circle centered on the fixed axis so that, due to symmetry, radiation patterns on the beam scanning surface are identical for all feed positions. The beam scanning surface so described permits an approximation to the specific surface defined by a group of lines drawn from an earth station site to points on the geostationary arc.

Thank you! Very interesting....