  A wide bandwidth, dual polarized, modified four-square antenna is presented
as a feed antenna for radio astronomical measurements. A linear array of these
antennas is used as a line-feed for cylindrical reflectors for Tianlai, a radio
interferometer designed for 21~cm intensity mapping. Simulations of the feed
antenna beam patterns and scattering parameters are compared to experimental
results at multiple frequencies across the 650 - 1420 MHz range. Simulations of
the beam patterns of the combined feed array/reflector are presented as well.
