Double-OAM-mode Generation by Octagonal Microstrip Ring Antenna

In this paper, a double-mode orbital angular momentum (OAM) antenna is proposed. By using an octagonal microstrip ring antenna with a matched load can generate orbital angular momentum (OAM) beams with different OAM modes at the same frequencies. When the inner ring is fed, this antenna can generate an OAM mode of $l=1$ at 5GHz. Similarly, when the outer ring is fed, vortex waves with $l=2$ can be generated. Because of its low profile and small size, this antenna is more potential in wireless communication, mobile devices, remote sensing and so on.