Ultra-wideband transmitarray antennas design based on ultrathin polarization conversion elements

Despite of various advantages, transmitarray antennas usually suffer from the limited bandwidth. In this paper, ultra-wideband polarization conversion elements are employed to design ultra-wideband linearly polarization transmitarray antennas. The proposed ultra-wideband transmissive polarization conversion element is a multilayered structure with asymmetric split circular ring structure in the middle layer and orthogonal metal gratings at the outermost layer. The element features ultra-wideband high efficiency transmission capability, a transmission phase coverage of 360 degrees and good phase linearity. By employing the proposed elements, an ultra-wideband linearly polarized transmitarray antenna with dimensions of 180 mm x 180 mm is designed and its highly efficient radiation performance is demonstrated by simulation. The designed transmitarray achieves 3 dB gain bandwidth of 61 %, ranging from 12.83 GHz to 24.09 GHz. The peak simulated gain is 28.13dB at 16.5GHz. In addition, the maximum aperture efficiency of the antenna is 54.13 % and the aperture efficiency is greater than 40% from 12.4 GHz to 18.4 GHz.