Abstract: A tracking system for use with an antenna having a multiple beam radiation pattern for sensing the direction of radiant energy incident upon the antenna. Pairs of the beams are selectively coupled to a monopulse comparator comprising a pair of hybrid couplers interconnected by a fixed phase shifter providing 90.degree. phase shift and by a pair of variable phase shifters providing phase shifts of equal magnitude but opposite sign. The output of the second hybrid coupler provides monopulse sum and difference signals. A sensing circuit responsive to the sum and difference signals operates the variable phase shifters to steer a null between the selected pair of beams.