A shared beamformer flexibly allocates beams among clusters of beams produced by phased array antenna apertures that are deployed on a satellite (or other type of platform). By sharing the beamformer among the beam clusters, if one beam cluster is not providing useful coverage, the beams may be reallocated to one or more other beam clusters that are providing useful coverage. To share the beamformer among the beam clusters, a selector network is used to select which particular beam cluster (or clusters) is used for producing one or more narrow beams that are constrained to the coverage area of the beam cluster (or clusters).