Optimum feeds for all three modes of a monopulse antenna II: Practice

In an amplitude-monopulse antenna whose main aperture is illuminated by a feed, it is desired to control the feed excitation independently in the sum, azimuth difference, and elevation difference modes. It is possible to describe a feed system, comprising an infinite array of radiators and hybrid junctions, which demonstrates the principle of complete independent control of the three modes. There are several practical feeds which approach a hypothetical ideal one in varying degrees. One representative type is the "twelve-horn feed;" although it has some disadvantages, it is versatile and quite useful. However the most attractive type for many applications appears to be one having a combination of multiple-horn excitation in one plane and multimode-waveguide excitation in the other. With a simple form of the "multihorn-multimode" feed, the ideal is substantially realized, and a major improvement in monopulse performance can be obtained.