An Ultrawideband 1-Bit Reconfigurable Reflectarray Element With Improved Angular Stability

In this paper, a 1-bit ultra-wideband reconfigurable reflectarray (RRA) element with improved angular stability is proposed. Based on the magneto-electric (ME) dipole, a novel central-patch probe structure is introduced, wherein two diodes are connected to opposite sides of the probe to control the two resonant modes. This configuration yields a fully symmetric RRA element, which balances and stabilizes the current distributions associated with both resonant modes, thereby enabling an ultra-wideband 1-bit phase response. Furthermore, rows of metallic vias are incorporated on both sides of the element to enhance the angular stability of the 1-bit phase bandwidth. Consequently, the proposed RRA element achieves a 1-bit relative phase bandwidth of 58% (8.97-16.44 GHz) and maintains this bandwidth at 33% for oblique incidence angles up to 50°. To experimentally validate the design, a 1×2 elements prototype was fabricated and characterized using the rectangular waveguide (RWG) method. The measured results exhibit good agreement with the simulations, thereby verifying the ultra-wideband performance of the proposed element. System-level simulations of a 16×16 array confirm that the proposed element significantly enhances the gain bandwidth and wide-angle scanning performances. These characteristics make the proposed RRA element a strong candidate for future radar, satellite communication, and reconfigurable intelligent surface (RIS) applications.