Broad-Band Multiple OAMs' Generation with Eight-Arm Archimedean Spiral Antenna (ASA)

Abstract

In this paper, an eight-arm Archimedean spiral antenna (ASA) is proposed to generate multiple orbital angular momentum (OAM) modes over a respectable frequency band (1.9-3GHz). Firstly, the principle of radiation by eight-arm ASA with right-hand spiral line is analyzed and simulated. It is demonstrated that the OAM modes and polarizations of the generated vortex waves are reconfigurable by changing the fed phases of the eight arms and controlling the radius of the antenna arm. Meanwhile, a prototype is fabricated and measured, in which experimental results agree well with simulation ones. At last, compared with other recently reported OAM-generating antennas, the proposed antenna with the smaller structure ( $\Phi 2.45\lambda _{0}$ , where $\lambda _{0}$ is the wavelength of the center frequency) can produce the higher gain (4.5-11.2dBi) vortex waves carrying multiple OAM modes (five modes) in the broad band of 1.9-3GHz.