Matching Theory of Cross-Polarization Suppression Components for Large-Scale Rectangular Waveguide Slot Array Antennas

In order to obtain good circular polarization, parallel metallic plates are used for large-scale rectangular waveguide slot array antennas to achieve pure linear polarization at first. It is found that these plates not only suppress cross-polarization, but also influence the original amplitude distribution of arrays for co-polarization. Though it is easy to obtain the proper plates length to achieve satisfying cross-polarization suppression. Plates with a specific length drastically perturb the array distribution, which leads to severe degradation of radiation performance. A matching theory for plates design is proposed and verified. It provides proper parameters for parallel metallic plates, and criteria for judging the design results. A practical array antenna is fabricated. Both the simulation and measurement results validate this theory. The theory gives guidance of designing similar external components for cross-polarization suppression or other functions, which is useful for slot arrays and other array antennas.