OAM Backhaul Link Supporting 1 Tbps over 1 km Transmission based on Cassegrain Antenna

Orbital angular momentum (OAM) beams present an inverted cone form and divergence. Consequently, the transmission distance and rate of the backhaul link based on OAM are severely limited. On the other hand, in the upcoming beyond fifth generation mobile communications (B5G) and sixth generation mobile communications (6G), the demand for communication distance between the macro base station (BS) and the self-backhaul small cell (SBSC) ranges from hundreds of meters to several kilometers, and the demand for transmission rate ranges between 100 Gbps to 1 Tbps. The OAM beam generated by the uniform circular array (UCA) exhibits inverted cone divergence. The difference in divergence angle between different modes can be two times or even more than three times. This makes it impossible to achieve long-distance and high-speed transmission simultaneously. In order to construct a 1-km and 1-Tbps OAM transmission system, this paper proposes a symmetric OAM transmission scheme using Cassegrain antennas. The Cassegrain antennas can converge the OAM beams and achieve high antenna gain. When the antennas are strictly coaxially aligned, backhaul links supporting a 1-km transmission distance and a 1-Tbps transmission rate are constructed. Further, the effectiveness of the backhaul link transmission scheme using symmetric Cassegrain antennas is verified through mathematical models, simulations and experiments.