Multiplexed antennas that sector-split in a first band and operate as MIMO antennas in a second band

Base station antennas include a plurality of multiplexer filters and a multi-column array of radiating elements that includes a plurality of sub-arrays. Each filter may have a first and second ports that are configured to pass RF signals in respective first and second frequency bands and a third common port that is coupled to a respective one of a plurality of sub-arrays. These antennas also include first frequency band ports that are coupled to the first ports of respective subsets of the multiplexer filters and second frequency band ports that are coupled to the second ports of at least some of the multiplexer filters. The antenna may operate as a MIMO sector antenna in the first frequency band and as a sector-splitting antenna in the second frequency band.