A monopulse antenna having independent optimization of the sum and difference modes

A monopulse antenna for a tracking radar has been developed which overcomes the usual need for compromise between sum and difference mode performance. The reflector of this antenna is illuminated by an unusual feed which enables independent optimization of all three modes: sum, azimuth difference, and elevation difference. The feed achieves suitably tapered illumination in all the modes by selective excitation of four stacked horns In one plane, and by utilization of three waveguide modes in each horn in the other plane. Measurements of the antenna confirm an improvement in both the azimuth and elevation difference modes of over 3 db increase in peak gain, and over 10 db further sidelobe suppression, while retaining the optimum sum-mode performance.