Study on Channel Characteristics of Terahertz Orbital Angular Momentum Communication System

Electromagnetic waves carrying orbital angular momentum (OAM) is considered as one of the candidate physical layer technologies for future 6G system thanks to its technical potential of improving the system capacity and spectral efficiency, and solving the problem of co-frequency interference. On the other hand, the terahertz (THz) frequency band, which has the potential to improve the data transmission rate with large bandwidth spectrum resources, has become the inevitable development trend of wireless communication. Thus, it is quite beneficial to further improve the system performance with the vortex electromagnetic waves in THz band. In this paper, a THz- OAM system based on uniform circular antenna array is proposed. The plane radiation distribution and channel characteristics of vortex electromagnetic waves at 0.22-THz are studied. The simulation results show that the THz vortex waves present obvious quantum state compared with lower frequency electromagnetic waves. The transmission distance, the radius of antenna array and the number of antenna elements could affect the characteristics of THz-OAM channel. The optimal OAM channel gain can be achieved when the number of transmitter and receiver antenna elements are set equal. The research on the channel characteristics of THz-OAM system, which considered the strong directivity of THz and the line-of-sight communication of OAM, provides a solution for short-range point-to-point high-speed communication in future wireless system.