Monopulse Antennas with Doubly Curved Reflectors

Doubly curved reflector antennas produce different cross-polarization components in the different directions of elevation because of the reflector´s curvature. In an one-plane monopulse system often used in the secondary radar case the cross-polarized components fill up the central null in the difference pattern. This effect is shown theoretically and experimentally. The beam width reduction by the monopulse system is therefore in most of the directions of elevation less effective. Hence there is a need of compensation or reduction of the cross-polarization. If the feed consists of dipoles the compensating components can be generated by different inclinations of the dipole stubs. With this technique the critical cross-polarization level in the difference pattern can be reduced by 10 dB typically. With a proper dimensioning a decrease of cross-polarization over the whole elevation angle region is possible.