  Recently, multi-mode antennas have been studied for communication as well as
localization purposes. In this work, the capabilities provided by a single
planar multi-mode radiator as a steerable multi-port antenna are explored. As
an original contribution, the radiation characteristics of individual groups of
modes of the single radiator are combined to optimize beamforming performance.
Three possible codebook realizations are studied and compared. A new
optimization criterion, gain by element factor, is introduced.
