Wideband Circularly Polarized High-Order Bessel Beam Reflectarray Design Using Multiple-Ring-Cascade Elements

In this letter, a wideband circularly polarized high-order Bessel beam reflectarray composed of 30x30 elements with different spatial orientations is proposed. The element is formed by a multiple-ring-cascade structure printed on the top surface of FR-4 substrate, an air layer, and a metal ground plane. The multiple-ring-cascade structure supports the multiple resonance property, which contributes in achieving the wideband circularly polarized performance. The reflection phase of 360. is achieved by continuously changing the spatial direction of the element. To validate the effectiveness of the proposed element, a high-order Bessel beam reflectarray with the size of 75 cm x 75 cm is designed, fabricated, and experimentally demonstrated. The measured results confirm that a high-order Bessel beam with l = + 1 is successfully generated from 5 to 8 GHz, which has less divergence in near-field transmission as compared to the vortex beam carrying the same orbital angular momentum mode.