LAUSR

In order to evaluate the transmission performance of orbital angular momentum (OAM) beams with a parabolic antenna, this letter investigates the attenuation of OAM beams reflected by the parabolic reflector. Specifically, the system structure and mathematical models of the OAM transmission with a parabolic antenna are established. According to the geometrical optics approximation and aperture field method, the electric field strength after the parabolic antenna is solved. In the case of the paraxial approximation, for the zero-order OAM mode, the receiving power is inversely proportional to the square of the transmission distance. However, for all the nonzero-order OAM modes, the receiving power is inversely proportional to the fourth power of the transmission distance. Compared with OAM beams generated by the traditional antenna array without the parabolic reflector, the receiving power can be improved greatly by the proposed structure with the parabolic reflector used for the OAM beam convergence. Especially for OAM beams with the high orders, the attenuation is no longer related to the OAM mode.