A Wideband Millimeter-wave Bidirectional OAM Antenna using sequential rotation feeding

A wideband bidirectional circularly polarized (CP) orbital angular momentum (OAM) antenna array is proposed for millimeter-wave frequency. The designed antenna array is composed of four bidirectional radiating dual-CP antenna units that rotate 90 degrees sequentially to each other in the clockwise direction. Results indicate that the left-hand circular polarization (LHCP) with a mode
$l_{OAM}=-1$
in +z direction and right-hand circular polarization (RHCP) with a mode
$l_{OAM}=+1$
in −z direction, over a wide impedance and 3-dB axial ratio (AR) relative bandwidth of 32.3% from 26 to 36 GHz.