  This paper describes the design of a 5.5:1 bandwidth feed antenna and
reflector system, intended for use in hydrogen intensity mapping experiments.
The system is optimized to reduce systematic effects that can arise in these
experiments from scattering within the feed/reflector and cross-coupling
between antennas. The proposed feed is an ultra wideband Vivaldi style design
and was optimized to have a smooth frequency response, high gain, and minimal
shadowing of the reflector dish. This feed can optionally include absorptive
elements which reduce systematics but degrade sensitivity. The proposed
reflector is a deep parabolic dish with $f/d = 0.216$ along with an elliptical
collar to provide additional shielding. The procedure for optimizing these
design choices is described.

Instrumentation and Methods for Astrophysics