Realization of Multimode OAM Beams with Almost the Same Divergence Angles

Yunfan Zhang,Junping Geng,Hongliang Wu,Weihao Qi,Xianling Liang,Qian Chen,Wei Wang,Mauro Parise

doi:10.1155/2021/6683622

Abstract

This paper proposes a new method of realizing multimode OAM beams with almost the same divergence angles. The theoretical relationship between the divergence angle of the OAM beam and its radiation source is presented, and the radiation source distributions for various mode OAM beams with the same divergence angle range are discussed. In order to verify this method, an eight-mode OAM antenna constructed by a bifocal parabolic reflector and dual OAM feeds is designed and simulated. The simulation results show that the divergence angle ranges of 3 dB beamwidth for OAM modesl=±1,±2,±3,±4are2.2°,4.6°,2.2°,5.0°,2.4°,4.4°, and 2.6°,4.8°, the divergence angles corresponding to the maximum beam directions are3.5°,3.6°,3.5°, and 3.8°, respectively, and the maximum difference is within0.3°.

Highlights

Since Allen et al first discovered OAM in 1992 [1] and ide et al verified the multiplexing transmission capability of OAM electromagnetic waves in the radio frequency band in 2007 [2], the research on OAM antennas has attracted widespread attention [3,4,5]
To achieve the same divergence angle for different OAM modes, Zhang et al proposed an OAM antenna based on a ring slit resonator, which can generate omnidirectional OAM beams [13], this method effectively realizes the consistency of beam divergence angles for various OAM modes, but the beam divergence angle is 90° due to its omnidirectional radiation
In order to achieve the abovementioned OAM source distributions of modes |l| 1, 2, 3, 4, we propose a bifocal parabolic reflector with dual OAM feeds, as shown in Figure 4. e reflector is composed of two paraboloids with different focal lengths (f1, f2 ) and aperture sizes (D1, D2 ), which are denoted by part A and part B. e geometric expressions of the two paraboloids are as follows: z P

Summary

Introduction

Since Allen et al first discovered OAM (orbital angular momentum) in 1992 [1] and ide et al verified the multiplexing transmission capability of OAM electromagnetic waves in the radio frequency band in 2007 [2], the research on OAM antennas has attracted widespread attention [3,4,5]. Many methods were proposed to generate OAM waves at radio frequency, such as crafted antennas [6], loop antennas [7], OAM phase plates [8], and circular antenna arrays [9, 10]. Qin et al proposed a four-mode UCA (uniform circular array) antenna design [14], through optimization of the element positions, and the beam with OAM modes of l −1, −2, and −3 and the divergence angle of 18° was generated simultaneously. A bifocal parabolic reflector antenna with dual OAM feeds is proposed as an example to achieve the corresponding equivalent source distributions and verify the design of eight-mode OAM beams with almost the same divergence angles

Theory and Analysis

Part A

Simulation and Discussion

Part B

Conclusion