通信学报

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论涡旋电磁波轨道角动量传输新维度

张超, 王元赫   

  1. 清华大学航天航空学院航空宇航电子系统实验室,北京 100084
  • 作者简介:张超(1978-),男,陕西城固人,清华大学航天航空学院教授、博士生导师,IET 会士、IEEE 高级会员、IEICE 高级会员。工信部IMT-2030(6G)无线技术工作组OAM 任务组组长。主 要研究方向为涡旋电磁波传输与探测,以及航空宇航电子系统。 王元赫(1997-),男,江苏涟水人,清华大学航天航空学院博士生,主要研究方向为电磁波轨 道角动量传输与探测。

New Dimension in Orbital Angular Momentum Transmission

摘要: 轨道角动量(OAM)是电磁波的固有物理量,与电场强度的物理量纲线性无关,所以相互独立,
可构成无线传输中的新维度。作为下一代移动通信中潜在关键技术的涡旋电磁波OAM 传输易与传统多天线
多输入多输出(MIMO)传输相混淆,从而引发关于涡旋电磁波OAM 是否在无线传输中提供新维度的争
议。本文从电磁波资源利用和发展的历史出发,分析了电磁波OAM 的物理特征,明确了只有电磁波量子携
带内禀OAM 的涡旋电磁波传输系统才可以获得MIMO 传输以外的无线传输新维度;统计态OAM 涡旋波束
中的电磁波量子形成的外部OAM 与空域维度相耦合,无法构成MIMO 传输以外的新维度,但在直射视距
(LoS)信道时可获得额外自由度和较低的复杂度。依据信道容量的不同,本文将典型涡旋电磁波OAM 传
输系统划分为四个不同区域,并着重指出量子态OAM 涡旋电磁波传输可以形成超越传统MIMO 容量界的含
有OAM维度的新MIMO 容量界。

关键词: 轨道角动量, 无线通信, 涡旋微波量子, 涡旋电磁波, 内禀轨道角动量

Abstract: Orbital Angular Momentum (OAM) is an intrinsic physical quantity in the Electro-Magnetic (EM) wave,
and the corresponding physical dimension is linearly independent with that of the electric field strength, so that the
OAM is independent with the electric field strength and constitutes the new dimension in the wireless transmission.
The vortex wave transmission system, which is the potential key technology in next-generation mobile
communications, is easily confused with the traditional Multiple-Input Multiple-Output (MIMO) transmission system.
This leads to the controversy on whether the OAM of vortex wave can provide the new dimension for the wireless
transmission. With tracing back to the history of EM wave utilization and development, the physical characteristics of
OAM are analyzed, and the fact that only the vortex wave transmission system with EM wave photon carrying
Intrinsic OAM (IOAM) can obtain the new dimension besides MIMO transmission is clarified. Compared with the
MIMO transmission, the Extrinsic OAM (EOAM) formed by the plane microwaves in the statistical OAM beam is
coupled with the space domain and cannot provide the additional new dimension. However, in the Line of Sight (LoS)
channel, the additional degrees of freedom and lower complexity can be achieved. Moreover, the typical vortex EM
wave OAM transmission system can be divided into four different regions based on the different channel capacities.
Taking the microwave band as an example, it is pointed out that only the quantum OAM transmission based on vortex
microwave photon can form a new MIMO bound with the OAM dimension beyond the traditional MIMO bound.

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