Theoretical Analysis And Comparison Of Oam Waves Generated By Three Kinds Of Antenna Array

Antenna array is one of the methods which can generate Orbital Angular Momentum (OAM) waves. However, OAM waves generated by different antenna arrays have different characteristics of Electric-field (E-field) components' distribution and radiation patterns. In order to solve this problem, we derive E-field formulas of OAM waves generated by different kinds of dipole antenna array in this paper. The dipole antenna arrays are arranged by three methods: 1) antenna elements are in the same direction of y axis, 2) antenna elements are in the radial direction and 3) antenna elements are in the azimuthal direction. Results show that x components, y components and z components carry different OAM modes under the three conditions. Simulation results show that the same direction antenna array produces the best OAM waves because the y component is dominated by OAM mode l and RHCP/LHCP waves are negligible in energy, while the pure OAM waves carried by the z components generated by the other two antenna arrays have little energy. In addition, only the radiation pattern of l = 0 produced by the same direction antenna array does not have a null zone in the propagation direction. Radiation patterns of l = +/- 1 do not have null zones in the propagation direction generated by other two antenna arrays.