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 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. , e.g. using an FDTD solver. But the enormous computational size of problems of this kind easily limits the practicality of using a full-wave solver. Â In this application note, first we consider investigate the radiation characteristics of a large parabolic reflector of manageable size illuminated by a waveguide-fed pyramidal horn antenna. We first solve the reflector-horn combination problem entirely using [[EM.TempoIllumina]] to establish a baseline for verification. NextThen, the we add a realistic pyramidal horn structure is taken out and enclosed in a Huygens box. A Huygens surface observable is defined and computed for feed to the [[EM.Tempo]] project. The parabolic reflector antenna is then transferred to [[EM.Illumina]] and it is illuminated by a Huygens source based on simulate the previously simulated data. combination antenna using [[EM.IlluminaTempo]]'s IPO full-wave FDTD solver is used to solve this hybrid problem. The results are then compared to the baseline FDTD results.
== A Note on Parabolic Reflectors ==