Fast and novel analysis of the EM radiation from large reflector antennas via Gaussian beams

A relatively simple procedure, which resembles a geometric theory for Gaussian beam reflection and diffraction, is developed for the fast analysis of electrically large reflector antennas. The feed radiation is expressed initially in terms of a relatively few sets of identical, rotationally symmetric vector Gaussian beams (GBs) with constant interbeam angular spacing. These GBs, which are launched from the feed region, are incident on the reflector surface and are thus reflected by it. A relatively simple, closed form expression has been developed for describing the fields associated with the reflection of a general electromagnetic (EM) astigmatic GB incident on an electrically large smooth surface. A closed form expression is also obtained for describing the diffraction of a general astigmatic GB by the curved reflector edge. Such a GB based analysis completely avoids the need for the conventional numerical computation of the physical optics (PO) integral for evaluating the fields radiated by reflector antennas. Some numerical results indicating the utility of this GB method are presented for the case of offset parabolic reflector antennas, although the method should be applicable to other smooth, electrically large reflector shapes.