A Reconfigurable Second-Order OAM Patch Antenna With Simple Structure

Using a single patch antenna to generate a vortex electromagnetic wave greatly simplifies the application systems of orbital angular momentum (OAM) modes. OAM modes can be synthesized from degenerate modes, and thus, characteristic mode theory is a helpful tool to guide the construction of OAM antennas. Based on this idea, a single-fed circular patch with an arc segment as a symmetrical perturbation element is proposed to radiate a second-order OAM wave. Since the arc segment is independent of the radiation element, it is easy to reconstruct the OAM mode order or vortex direction by adjusting it. In this regard, two symmetrical arc segments switched on and off using p-i-n diodes are applied to implement the reconfiguration of the second-order OAM mode. The structure effect on the vortex wave is discussed by using modal weighting coefficients.