Contents 1. Introduction
Typical dual reflector antenna design requires a feed antenna that properly illuminates the subreflector to produce the desired far field pattern of the antenna system. It is very common to have a feed antenna that provides a −10 to −15 dB edge illumination on the subreflector to obtain optimal performance of the overall antenna system. With the dual reflector antenna system as shown in Figure 1, the electrical size of the feed antenna can have an aperture of a few wavelengths in diameter to provide the proper illumination. Typical design steps involve (1) Feed design that has very good VSWR and (2) Use the far field pattern to compute the illumination on the subreflector and subsequently the main reflector to determine the far field pattern of the whole antenna system. For most communication system, this design approach works fine to satisfy the performance requirement. However, in some very high performance system in communication and radar applications, the above design procedure may not be sufficient to determine the actual performance of the antenna, mainly due to the structure scattering of the relatively large horn antenna which no one has taken into account during the design phase.
