Dual-Band Miniaturized Linear-to-Circular Metasurface Polarization Converter With Wideband and Wide-Angle Axial Ratio

A dual-band miniaturized linear-to-circular polarization converter (LCPC) metasurface with wideband and wide-angle axial ratio (AR) is proposed and demonstrated. The metasurface is formed with periodic arrays of unit cells. The unit cells consist of three metallic layers separated by two substrates. The top and bottom metallic layers contain the identical cells with two metal strips and an “I”-type strip with four stubs for <inline-formula> <tex-math notation="LaTeX">$y$ </tex-math></inline-formula>-polarization each. The middle metallic layer comprises an infinitely long metal strip and two “I”-type strips for <inline-formula> <tex-math notation="LaTeX">$x$ </tex-math></inline-formula>-polarization. The LCPC performs a wideband response in both operating bands with the wide passbands generated by the orthogonal “I”-type strips. Prototyped <inline-formula> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula>-/ <italic>Ka</italic>-band design shows that the simulated/measured AR remains below 3 dB over the lower bandwidth of 15–21.2 GHz (34.3%)/16.3–21.1 GHz (25.7%) and higher bandwidth of 27–30.3 GHz (11.5%)/27–29.8 GHz (9.9%) under normal incidence in <inline-formula> <tex-math notation="LaTeX">$y-{z}$ </tex-math></inline-formula> plane, respectively. For a 45° incidence, the measured AR still achieved the 3 dB bandwidth of 33.7%/9.4% in both the bands. The study shows that by virtue of orthogonal structures placed at different layers, the element size and the cross-polarization level are suppressed by 65% and 10 dB, respectively, compared to the previous work. Furthermore, the LCPC with the miniaturized elements shows wide-angle response in both the bands.