Planar millimetre-wave antenna simultaneously producing four orbital angular momentum modes and associated multi-element receiver array

The authors present the design and simulation of a planar Bull's eye antenna that can simultaneously produce four orbital angular momentum (OAM) modes with up to 2.4 GHz impedance bandwidth at 60 GHz. OAM modes l = ±3, ±13 are produced simultaneously by two ring resonators in the centre of the antenna. The peak gain is 13.1 (8.1) dBi at ±10 (±25) degrees for mode l = ±3 (±13), with all modes present over a 30° angular range (15–45° from the boresight). For reception and demultiplexing, the authors use a discretely sampled partial aperture receiver (DSPAR), and show algebraically that such systems can achieve ideal mode orthogonality in cases where existing partial aperture receivers cannot. The authors present a DSPAR design to complement the Bull's eye antenna, needing only four simple receiving elements and hence more readily scaling to work over longer link distances than systems relying on horn antennas with integrated spiral phase plates.