Analytical High-efficiency Spot-beam Model for High Throughput Satellites

We develop a simple model for a feed horn with a uniformly excited circular aperture at the focus of an offset paraboloidal reflector antenna and compare it with reflector antenna analyses using combinations of circular waveguide TE1n modes. The model demonstrates the deep dip that can occur at the spot-beam center for certain feed diameters and it is used in a design procedure that relates the feed and the spot-beam diameter. The model may be extended to include feed horn flare effects.