Matching Theory of Cross-Polarization Suppression Components for Large-Scale Slot Array Antenna with High-Gain Horn

In order to achieve circular polarization, parallel metallic plates are applied to large-scale slot array antenna with a high-gain horn to obtain pure linear polarization at first. Based on a practical slot array antenna, it is found that these plates not only suppress cross-polarization, but also have band-notched performance for co-polarization at a wide potential notched band. Theoretically, the plates and horn form short horn waveguides with cut-off characteristics to suppress cross-polarization. However, according to simulation and measurement results, the horn waveguides are actually non-closed qusi-horn waveguides because of engineering errors. By transmission line models, it is found that qusi-horn waveguides have two notched bands related to the notched performance of parallel-plate and horn waveguides respectively. Based on these, a matching theory for cross-polarization suppression components and slot array antennas are proposed and validated. This theory gives guidance to design of similar components and array antennas which need to matching co-polarization while suppressing cross-polarization in practical projects.