Generating Concentrically Embedded Spatially Divided OAM Carrying Vortex Beams Using Transmitarrays

To effectively exploit the orbital angular momentum (OAM) characteristics, it is essential to have devices which are capable of generating beams with multiple OAM modes simultaneously. Most of the proposed techniques commonly require time division multiplexing at the transmitter side or beam splitters at the reception side for separating OAM modes and directing beams of different OAM modes to different directions. To overcome this problem, here, the concept of aperture sharing for generating concentrically embedded OAM-carrying beams is presented. Such a methodology provides embedded beams of various OAM modes which are launched toward a single direction through a shared aperture of transmitarray (TA), while having a spatial division between them. In this manner, the transmitted beams are initially separated by the hardware at the transmitter level. A novel circularly polarized (CP) substrate-coupled unit cell is designed and used as the elemental components on the aperture of the TA. Three prototype TAs are realized for investigating different cases of the OAM modes embedding and verifying the effectiveness of the proposed method. The obtained simulated and experimental results are consistent which validate the novel technique.