1.College of Big Data and Information Engineering, Guizhou University, Guiyang 550025, China 2.Key Laboratory of Micro-Nano-Electronics and Software Technology of Guizhou Province, Guizhou University, Guiyang 550025, China 3.Engineering Research Center of Power Semiconductor Device Reliability, the Ministry of Education, Guizhou University, Guiyang 550025, China
Fund Project:Project supported by the National Natural Science Foundation of China (Grant No. 61961006) and the Science and Technology Foundation of Guizhou Province, China (Grant No. QKHJC [2020]1Y257)
Received Date:13 June 2021
Accepted Date:12 July 2021
Available Online:17 August 2021
Published Online:05 December 2021
Abstract:Orbital angular momentum (OAM) vortex electromagnetic waves can provide a new degree of freedom for information modulation at a physical level, which has great prospects of applications in the fields of wireless communication and radar imaging. The application of beam scanning techniques of phased array to OAM vortex electromagnetic wave can increase its communication coverage and expand the detection coverage of vortex radars. Firstly, in this paper, the principle of generating the beam steering vortex electromagnetic beam is discussed and the compensated phase formula for generating beam steering OAM beams is given by planar phased array. Secondly, considering the advantages of phased array antennas in beam scanning and OAM reconfigurability, a planar phased array with 8 × 8 antenna elements at 10 GHz is designed and fabricated. The performances of OAM beam steering and mode reconfigurability are verified. Finally, the performance changes of the deflecting OAM vortex beam at different scanning angles are discussed and analyzed. Simulations and measurements both show that there exist pattern distortion problems when steering angle of OAM beam becomes large. In this paper, the variation of the OAM mode purity is also studied when the scanning angle and the OAM mode number change. The results show that the planar phased array antennas can effectively generate the beam steering OAM vortex beams in a certain angle range. Hence, this paper can provide a reference for the OAM vortex electromagnetic wave communication and the vortex radar in the future. Keywords:orbital angular momentum/ vortex wave/ beam steering/ planar phased array
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2.1.涡旋波束扫描原理
如图1所示, 当OAM涡旋电磁波束的指向为任意角度(θ, φ)时, 可以通过坐标旋转变换设置一个相对直角坐标系$X'Y'Z' $, 使得波矢k的方向与$Z' $轴重合. 在此条件下, 用平面阵天线生成OAM波束, 平面阵上各单元的相位Φ可表示为 图 1 用于产生涡旋电磁波的平面阵列天线示意图 Figure1. Schematic diagram of the planar array for generating vortex waves.