A feed system for spherical reflector

The present paper gives a simple method for synthesising a feed system for the spherical reflector to minimise the phase error "spherical aberration." The spherical reflector is considered as if it were consisting of several subsurfaces each approximating a certain hypothetical paraboloidal surface, resulting in several paraboloidal surfaces having parallel axes and different foci. The proposed feed system consists of several feeds located at these foci and arranged such that every one illuminates the corresponding subsurface of the reflector. The feeds are phased so that the reflector aperture is illuminated in phase. A feed system consisting of five feeds is designed, yielding a maximum phase error of 0.00079, with
\pm 38\deg
angle scanning.