The bandwidth of OAM antennas, which have a great potential for multiple-input multiple-output (MIMO) communication, must be wide enough. Unfortunately, most of researchers only care about the generation and characteristics of vortex beams carrying orbital angular momentum (OAM) but ignore the bandwidth of OAM antennas. To develop OAM antenna suitable for MIMO communication, Vivaldi antenna is used as the element of circular array because of its wide bandwidth. Three compact wideband circular Vivaldi antenna arrays that can generate vortex beams carrying OAM with numbers of modes l=0, -2, +2 are proposed and experimentally validated in this paper. Measured results show that the proposed antennas can radiate vortex beams with different numbers of modes over a frequency range of 2.7-2.9 GHz.
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