An Ultrathin Linear-to-Circular Polarization Converter with Wide Axial Ratio Bandwidth

In this paper, an ultrathin transmission-type linear-to-circular polarization (LCP) converter is designed for X-band using a simple bi-layer frequency selective surface. The proposed polarization converter converts the TE- (or y-) and TM- (or x-) polarized incident waves into left-handed circularly polarized (LHCP) and right-handed circularly polarized (RHCP) transmitted waves, respectively. It offers 42.4% (8 - 12.3 GHz) 3 dB axial ratio bandwidth (ARBW) to the LHCP transmitted wave while it possesses only 0.027λ
0
thickness (λ
0
is the wavelength at the mid-operating frequency). Moreover, the converter is quite insensitive to the oblique incident waves. The polarization state of the transmitted wave is characterized by determining the actual polarization ellipses at few frequency samples. The measurement results show good agreement with the numerically simulated results.