涡旋电磁波的产生、接收与成像应用研究

发布时间：2018-04-26 19:36

本文选题：轨道角动量 + 涡旋电磁波　；参考：《中国科学院大学(中国科学院国家空间科学中心)》2017年硕士论文

【摘要】：轨道角动量是涡旋电磁波的新自由度,不同的轨道角动量可以构成无穷维模态空间中的正交基,有多路复用以提高频谱效率解决电磁频谱拥挤问题的潜力。涡旋电磁波的幅度具有第一类贝塞尔函数的形式,辐射场对于成像区域有着不同的权重,容易突破天线孔径实现天线波束内的超分辨率成像。本文的目的是对基于均匀圆形天线阵的涡旋电磁波的产生与接收进行误差分析,得出能够准确判别轨道角动量模态的误差阈值,明确轨道角动量各接收方案的接收条件,为涡旋电磁波的产生与接收提供技术参考。同时对涡旋电磁波在雷达探测与成像方面的应用潜力进行探索与评估。本文首先研究了天线阵元激励幅度和相位存在高斯分布误差、量化误差、单个阵元误差以及均匀圆形天线阵的阵元个数对所产生的涡旋电磁波的幅相特征的影响,利用相位梯度法计算了轨道角动量模态并给出准确辨认模态时的各误差阈值。仿真实验显示,在各类激励幅度和相位误差下,涡旋电磁波有效幅射区域的幅度会由环状变得不规则,相位在有效辐射区域内保持良好,而在幅度强度很低的中心和边缘出现了模糊与恶化。实验结果说明,涡旋电磁波对各类激励幅度和相位误差具有良好的抗干扰特性。论文对均匀圆形天线阵的接收方案进行了误差分析,分析了均匀圆形天线阵接收阵列与发射阵列不平行的情况下,涡旋电磁波的幅度与相位的改变。结果表明,涡旋电磁波对均匀圆形天线阵有倾斜角的误差具有很强的敏感性,甚至在3度的倾斜角误差下涡旋电磁波的相位分布已不能分辨出轨道角动量的模态。另外,明确了涡旋电磁波的各接收方案的接收条件。最后,论文对涡旋电磁波在雷达探测与成像中的应用进行了研究。根据涡旋电磁波的幅度中空特征选择了侧视成像体制,建立了涡旋电磁波的成像模型,利用最小二乘的关联算法成像。仿真结果表明,同参数下与传统信号的成像分辨率相比,涡旋电磁波将分辨率提高了1.8倍。对涡旋电磁波的成像结果进行了评价:由于涡旋电磁波幅度的圆对称以及中空结构特征,对成像分辨率的提升能力有限;涡旋电磁波所形成的信号参考矩阵条件数很高,表明具有较大的病态性;随着信噪比的增加,成像结果以及均方根误差均会有一定的改善。
[Abstract]:Orbital angular momentum is a new degree of freedom of vortex electromagnetic wave. Different orbital angular momentum can form the orthogonal basis in infinite dimensional mode space and has the potential of multiplexing to improve the spectral efficiency to solve the problem of electromagnetic spectrum congestion. The amplitude of vortex electromagnetic wave has the form of Bessel function of the first kind, and the radiation field has different weights for the imaging region, so it is easy to break through the antenna aperture to realize super-resolution imaging in the antenna beam. The purpose of this paper is to analyze the error of vortex electromagnetic wave generation and reception based on uniform circular antenna array, to obtain the error threshold which can accurately distinguish the orbital angular momentum mode, and to determine the receiving conditions of each receiving scheme of orbital angular momentum. It provides a technical reference for the generation and reception of vortex electromagnetic wave. At the same time, the application potential of vortex electromagnetic wave in radar detection and imaging is explored and evaluated. In this paper, the effects of Gao Si distribution error, quantization error, single element error and the number of array elements of uniform circular antenna array on the amplitude and phase characteristics of vortex electromagnetic wave are studied. The phase gradient method is used to calculate the orbital angular momentum modes and the error thresholds for identifying the modes are given. The simulation results show that the amplitude of the effective radiation region of vortex electromagnetic wave changes from annular to irregular under various excitation amplitude and phase error, and the phase keeps well in the effective radiation region. At the center and edge where the amplitude intensity is very low, there is blur and aggravation. The experimental results show that the vortex electromagnetic wave has good anti-interference characteristics to all kinds of excitation amplitude and phase error. In this paper, the error analysis of the receiving scheme of uniform circular antenna array is carried out, and the amplitude and phase of vortex electromagnetic wave are analyzed when the receiving array of uniform circular antenna array is not parallel to the transmitting array. The results show that the vortex electromagnetic wave is very sensitive to the error of the uniform circular antenna array with inclination angle, and even the phase distribution of the vortex electromagnetic wave can not distinguish the orbital angular momentum mode under the angle error of 3 degrees. In addition, the receiving conditions of each receiving scheme of vortex electromagnetic wave are determined. Finally, the application of vortex electromagnetic wave in radar detection and imaging is studied. According to the amplitude and hollow characteristic of vortex electromagnetic wave, the lateral imaging system is selected, the imaging model of vortex electromagnetic wave is established, and the least square correlation algorithm is used to image the image. The simulation results show that the resolution of the vortex electromagnetic wave is 1.8 times higher than that of the conventional signal under the same parameters. The imaging results of the vortex electromagnetic wave are evaluated. Due to the circular symmetry of the amplitude of the vortex electromagnetic wave and the hollow structure, the lifting ability of the imaging resolution is limited, and the condition of the signal reference matrix formed by the vortex electromagnetic wave is very high. With the increase of SNR, the imaging results and the root mean square error will be improved to some extent.
【学位授予单位】：中国科学院大学(中国科学院国家空间科学中心)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN820.15

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