G T MAXIMIZATION OF A PARABOLOIDAL REFLECTOR FED BY A DIPOLE-DISK ANTENNA WITH RING BY USING THE MULTIPLE-REFLECTION APPROACH AND THE MOMENT METHOD/

A 1.8-m paraboloidal reflector fed by a dipole-disk antenna with a bea mforming ring is optimized far high G/T at L-band by using the moment method (MM) and the multiple reflection (MR) approach, The MR approach is based on using MM to calculate the radiation and scattering patter ns of the feed, using physical optics plus uniform geometrical theory of diffraction (UTD) to include the reflector, and in addition to incl ude the mutual interaction (multiple reflections) between the reflecto r and the feed by using the expression for the sum of an infinite geom etric series. The MR approach is shown to be equally accurate as a MM solution of the complete antenna with reflector, provided the reflecto r is in the far field of the feed, and the MR approach is much faster, As a result of the calculations using the MR approach, design curves are presented showing how the G/T varies as a function of antenna geom etry, size, and elevation angle, all for a given noise profile of the surrounding sky and ground. The computed radiation patterns and G/Ts a re compared with measurements for several elevation angles and surroun ding terrain.