Generating Mode 1/-1 Circularly Polarized Nonvortex OAM Beams Using Uniform Circular Arrays

In this paper, uniform circular arrays (UCA) capable of generating non-vortex mode 1/-1 circularly polarized orbital angular momentum (OAM) beams are designed and simulated. The generated OAM beams have the characteristic helical phase front, but the radiation pattern does not have a null at the center in the direction of propagation. This is in contrast to the typical OAM beams, which not only carry the helical phase fronts but also have a null at the center of their radiation patterns. This is achieved by applying the OAM mode 1/-1 excitation phases to the antenna elements and sequentially rotating the antenna elements of the UCA by an amount equal to their excitation phases. Furthermore, it is shown that the rotation and the excitation phases conflate to result in a circularly polarized beam. Several examples of such arrays designed at 17.8 GHz operating frequency are presented via full-wave simulations in the CST Microwave Studio software. Such non-vortex OAM beams could enable high data rate long-range communications by multiplexing several beams.