基于电磁涡旋的旋转物体探测机理及方法研究

Electromagnetic vortex, i.e., electromagnetic waves carrying orbital angular momentum (OAM), is becoming a hot topic worldwide in recent years. Electromagnetic vortex possesses rotational properties due to its helical phase fronts. It has been found that when electromagnetic waves with OAM illuminate on a rotating surface, a frequency shift can be observed, which is called the rotational Doppler effect. Because electromagnetic vortex has the transverse momentum which is perpendicular to the propagation direction, the observed frequency shift is proportional to the OAM modes and the rotational speed of the objects. The traditional linear Doppler effect has been widely used to measure the velocity of moving objects, but it cannot detect the rotational speed of objects. The rotational Doppler effect of electromagnetic vortex can be utilized to detect the objects with rotational components, especially useful for the motionless objects with rotating parts, such as helicopters. The study of the rotational Doppler effect currently is only focused on the optical spectrum. This project proposes to investigate the rotational Doppler effect in the microwave/mm-wave spectrum, a new spectrum for rotational Doppler effect applications. The operating mechanism of the rotational Doppler effect will be studied for practical rotational components, such as rotational propellers. The rotational Doppler effect will be applied to the detection of real objects with rotational components, such as unmanned aerial vehicles (UAVs), helicopters, and ships.

电磁涡旋，即带有轨道角动量的电磁波，是当前国内外的研究热点。电磁涡旋因其螺旋形相位面而具有旋转特性：研究表明当带有轨道角动量的电磁波入射到旋转平面时，可以观察到频率的偏移，这被称之为旋转多普勒效应。由于电磁涡旋具有垂直于传播方向的横向动量，所观察到的频率偏移正比于轨道角动量模式和平面旋转速度。利用传统线性多普勒效应可以探测物体的运动，但不能探测物体的旋转。而应用电磁涡旋的旋转多普勒效应，可以实现对带有旋转部件的物体探测，特别是对静止的带有旋转部件的物体探测更具独特优势。目前旋转多普勒效应研究仅限于光学频段，项目开展微波与毫米波频段的电磁涡旋旋转多普勒效应研究，具有学术创新性；项目研究电磁涡旋对实际旋转体（如螺旋桨）的旋转多普勒效应的形成机理，具有实用的理论意义；项目应用电磁涡旋实现对无人机，直升机，舰船等带有旋转部件的实用物体探测，探索有效可行的探测方法，具有重要的实际意义和工程应用价值。

项目围绕利用轨道角动量（OAM）涡旋电磁波实现旋转物体探测的理论机理与实现方法开展系统研究，包括多模态OAM涡旋电磁波的产生方法，多模态旋转多普勒效应的探测机理，以及基于多模态OAM涡旋电磁波的隐身机理与实现方法。提出了可重构多模态OAM涡旋电磁波概念和实现方法，通过控制/调整超表面的反射特性，实现多种不同的OAM模态，为涡旋电磁探测提供不同模态的OAM波束，对涡旋电磁探测系统的实现具有重要科学意义；实现了利用OAM涡旋电磁波探测旋转物体的旋转多普勒频移，为涡旋电磁探测提供了实现方法，具有重要应用价值；探讨了基于时空调制超表面的多普勒隐身斗篷，通过控制超表面的OAM模态，实现不同运动/旋转物体隐身，为物体隐身技术提供了新的技术途径，具有潜在应用前景。项目正继续开展基于涡旋电磁波的旋转物体高效探测方法研究，深入探索理想与非理想情况下回波模型及其参数提取以及旋转物体目标分类对涡旋电磁探测的影响。项目还开展了其它多频宽带集成/共口径融合天线研究，为涡旋电磁探测提供坚实的天线理论与技术保障。项目资助发表SCI收录国际期刊论文15篇，授权国家专利15项，其中发明专利2项，资助培养出站博士后1名，毕业博士生1名，毕业硕士生10名，在读博士生2名，在读硕士生5名，获优秀学生论文奖1名。