Circularly Polarized and Linear Polarized Mode Multiplexing OAM Antenna Using Sequentially Rotated Technique

A circularly polarized (CP) reconfigurable and linear polarized (LP) orbital angular momentum (OAM) mode multiplexing concentric uniform circular array (CUCA) is presented. The designed antenna array consists of two parts: an inner UCA composed of four LP antenna elements and an external UCA composed of eight sequentially rotated CP reconfigurable elements. The inner UCA and outer UCA are capable of generating multiplexed OAM beams at 3.28 GHz with l = +1 and mode l = ±2, respectively. To assess the performance of these vortex beams, a purity analysis of the multiplexed OAM modes was conducted. When all elements are fed with the same amplitude signal, the mode purity of the inner UCA at l = +1 with LP is 27.6%. As for the external UCA, at l = +2 with right-hand CP (RHCP), the mode purity in the electric field Ex- component is 32.5%, and in the Ey- component, it is 47.5%. Furthermore, l = −2 with left-hand CP (LHCP) has similar results. The obtained results are consistent, validating the potential application of the proposed modal multiplexing method in future communication.