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 30×30 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
$^\circ$
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 × 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.