OAM Backhaul Link Supporting 1 Tbps Over 1-km Transmission Based on Cassegrain Antennas

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 (B5G) mobile communications and sixth-generation (6G) mobile communications, 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 Gb/s and 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 Tbps OAM transmission system, this article proposes a symmetric OAM transmission scheme using cassegrain antennas (CAs). The CAs 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. Furthermore, the effectiveness of the backhaul link transmission scheme using symmetric CAs is verified through mathematical models, simulations, and experiments.