== Introduction ==
Parabolic reflectors are typically used a high-gain antenna due to their electrically very large aperture dimensions. The Physical Optics (PO) technique can solve reflector problems efficiently when the details of the feed mechanism can be neglected. For example, a parabolic reflector with a very large focal length can be modeled using a Hertzian short dipole radiator placed at its focal point. Besides the conventional Geometrical-Optics-Physical-Optics (GOPO) technique, [[EM.Illumina]] ([[EM.Cube]]'s PO Module) offers a generalized Iterative Physical Optics (IPO) solver. IPO effectively compensates for the shortcomings of GOPO with regard to multiple shadowing effects and handling of concave surfaces that support multi-bounce rays. Therefore, IPO is a good candidate for solving large parabolic reflector antenna structures. The basic steps of simulating a parabolic reflector antenna using the IPO solver are describd described in detail in [[EM.Illumina Tutorial Lesson 3: Computing The Radiation Pattern Of Parabolic Dish Reflectors]].
In many realistic situations, however, the reflector's feed structure cannot be approximated as a simple point source or it may even cause blocking effects. In problems like this, a full-wave simulation of the entire structure is needed. In this application note, first we investigate the radiation characteristics of a large X-band parabolic reflector at 10GHz using [[EM.Illumina]]. Then, we add a realistic pyramidal horn feed to the reflector and simulate the combination antenna using [[EM.Tempo]]'s full-wave FDTD solver.