基于聚合型涡旋电磁波束的三维SAR成像

合成孔径雷达(synthetic aperture radar, SAR)能够突破天线孔径对分辨率的限制，因而得到了广泛应用. 本文提出了一种基于聚合型涡旋电磁波束的三维SAR成像方法，通过设计合适的成像几何构型，利用涡旋电磁波的相位特性实现对高度维的分辨，并推导得到高度维分辨率与模式数及雷达参数之间的关系. 考虑到回波信号中引入的涡旋相位项，对后向投影算法进行改进，实现对观测区域的三维成像，并引入稀疏重构算法减少对模式数的需求. 仿真结果表明，利用多模式聚合型涡旋电磁波束能够对分布在不同高度的目标进行准确重构，利用稀疏重构算法能够用少数模式实现高分辨三维成像. 本文提出的方法为新体制雷达成像研究提供了一定的参考.

Three dimensional SAR imaging based on the focused electromagnetic vortex beam

Synthetic aperture radar(SAR) is widely applied since it can break through the limitation of resolution by antenna aperture. In this paper, the focused electromagnetic(EM) vortex beam is applied to synthetic aperture radar to realize 3D imaging. By appropriately designing the imaging geometry, height resolution can be achieved with the use of the phase characteristics of EM vortex wave, and the relationship between height resolution and the number of orbital angular momentum(OAM) mode and radar parameters is derived. Considering the vortex phase term introduced in the echo signal, the improved back projection algorithm is applied to realize 3D imaging, and then sparse recovery algorithm is introduced to reduce the demand of the number of OAM mode. Simulation results indicate that the targets distributed at different heights can be accurately reconstructed, and high resolution is realized by sparse recovery method with few OAM modes. The method in this paper provides a certain reference for the research of new radar imaging system.