Single-Layer, Multimode OAM Reflectarray Antennas

In this letter, an innovative reflectarray (RA) antenna able to radiate in the same direction multiple orbital angular momentum (OAM) modes, is presented: depending on the direction of arrival of the impinging field, the RA radiates a broadside beam carrying on an OAM mode with different index. Two circular RAs with diameter
$D = 19.8\lambda$
at the the frequency
$f_{0} = 30\,$
GHz, able to radiate two or four OAMs, have been designed and simulated, while a prototype of the dual-mode configuration has also been manufactured and experimentally characterized. The obtained results prove that vortex beams are successfully generated in the range of frequencies from 28 to 32 GHz, confirming the effectiveness of the proposed design.