A Circularly Polarized Horn Antenna Based on an FSS Polarization Converter

This letter designed a circularly polarized horn antenna by loading a frequency selective surface (FSS) polarization converter at the aperture of a standard horn. The proposed polarization converter is based on multilayer nonresonant FSS. It is composed of a two-layer dielectric slab and three printed metal layers, which are etched on the top, middle, and bottom layers of the slab. The three metal layers consist of a two-layer patch with a square truncated corner and a one-layer grid line with a slot. By introducing perturbation to both the patch and the grid line, the polarization converter shows a low profile and subwavelength unit size, whose dimension is 0.18 lambda(0) x 0.18 lambda(0) while the thickness is only 0.1 lambda(0). The simulated results show that the axial ratio (AR) is less than 3 dB in the frequency range of 9.6-11.7 GHz, i.e., a fractional bandwidth of 19.7% within the targeted frequency band. The measurement results are in a good agreement with the simulation results, which proves the feasibility of the design.