基于电磁涡旋的雷达目标成像

作为信息载体的电磁波除了传统的携带信息方式外，近年来其波前以电磁涡旋形式展现的信息调制能力也越来越受到关注。本文综述了电磁涡旋在信息调制等方面的研究进展，阐述了其在雷达信息获取方面的潜在应用价值。针对圆形相控阵列，建立了电磁涡旋波照射下理想点散射目标的回波模型。将各阵元的接收信号按照与发射时相同的模式移相后，沿圆周积分即可获得雷达阵列的输出回波。该回波可表示为经平方Bessel函数调幅后的傅里叶基函数的线性组合。结合Bessel函数的频谱特性，分析了轨道角动量态与方位角变量之间的近似对偶关系，利用逆投影和滤波-傅里叶变换方法进行了成像处理。仿真实验表明，电磁涡旋对雷达目标具有方位向成像的潜力。本文的研究可为新体制的雷达设计、目标识别技术的发展提供参考和借鉴。

Electromagnetic vortex based radar target imaging

Amplitude/frequency/phase modulation of electromagnetic(EM) wave are the common ways of carrying information. However, it has received intensive attention recently when the wave front acts as EM vortex for information modulation. In this paper, the progress on the information modulation capability of EM vortex is systematically summarized and its potential on radar information acquisition is also introduced. Aiming at the circular phased array, the echo signal model of ideal point target is established under the illumination of EM vortex wave. Once the echo signal phase of each antenna element is shifted with the same mode as applied for submission and integrated along the circular path, one can obtain the output signal of the radar array. The output signal can be modeled as the linear superimposition of Fourier basis with the amplitude modulated by squared Bessel function. According to the spectrum characteristic of Bessel function, the approximate dual relationship between the mode number of orbital angular momentum(OAM) and the variable of azimuthal angle is analyzed. Finally, the back projection(BP) algorithm and filtered FFT based algorithm are applied to image the target. Simulations show that electromagnetic vortex wave has the potential to acquire the cross-range profile of the radar target. The research in this paper may act as a reference to the design of new mechanism radar and the development of target recognition technology.