A Wideband Circularly Polarized Transmitarray Using Parallel Dielectric Plate-Based Unit Cells With Negative Anisotropy Slop

A solution to enhance the axial ratio (AR) bandwidth of a circularly polarized (CP) planar transmitarray using 3-D printed parallel dielectric plate unit cells is presented here. Unlike the conventional anisotropic structure with positive anisotropic slope property, a structure with negative anisotropic slope property is proposed, which exhibits a wider polarization conversion bandwidth. By further incorporating element rotation and geometrical variation, a six-state phase adjustment scheme is adopted to design a 540-element circular-aperture CP transmitarray. Promising results are demonstrated experimentally, showing an aperture efficiency of 41%, a wide 1 dB gain bandwidth of 25% and an overlapped 3 dB gain and AR bandwidth of 42.4%. With these substantial advancements, the proposed approach opens exciting avenues for designing wideband polarizers and discrete lenses based on 3-D-printed anisotropic structures.