Radiation properties of the optimized offset-fed radial rib umbrella reflector antenna

The properties of the offset-fed radial rib umbrella reflector are analyzed. A simple formula for positioning the feed to maximize the gain is given. The best aim point for the feed is numerically determined to be very close to the rib center. The exponent of a
\cos^{n} \alpha
feed pattern, evaluated for maximum gain, and the loss due to the gores is presented. It is shown that the offset configuration exhibits the same behavior and position of the gore-related sidelobe as the front-fed umbrella reflector.