In the paper, an alternative formulation for an optimum beamformer with a robustness capability against directional errors is presented. With this approach, the width of the main beam can be specified and a compromise can be reached between a reasonable signal acceptance angle and the ability of the beamformer to reject directional interferences. Furthermore, based on a partitioned processor interpretation, the new beam-former gives a clue to a way of reducing the complexity of a full processor.