Numerical validation of arecibo-based analytical hat antenna theory using canonical PEC/PMC strip grids

The hat antenna is a self-supported rear-radiating waveguide feed used in the Comhat reflector that has been manufactured in more than 1M pieces for use in radio links. The design of hat feeds is done by numerical simulations taking advantage of its rotational symmetry. There exists an early analytical model for the far-field of the hat feed including the axial waveguide, and treating the hat brim as a PEC/PMC strip grid. The purpose of the present paper is to validate the theoretical model by simulations using COMSOL Multiphysics.