Electronically controlled phase center locations in electrically large aperture antennas with enhanced cross-talk properties

The cross polarization performance of an electrically large aperture antenna, capable of providing adaptive multi-phase center locations within its aperture, is addressed in this paper. Such adaptive operation is realized using an offset parabolic reflector antenna, illuminated by a dual-mode circular waveguide feed at the TE₁₁ and TE₂₁ modes. The amount of the phase center displacement is then dependent on the strength of the mode content factors of the primary feed. It is shown that when the phase center is electronically displaced over the reflector aperture with such a dual-mode feed, the cross polarization performance deteriorates. This can be alleviated by introducing an extra TM₁₁ mode to the waveguide feed, without affecting the phase center locations of the compound reflector and the feed.