基于时间反演的自适应聚焦天线阵列研究

发布时间：2018-12-11 19:56

【摘要】：时间反演是一种自适应空时聚焦技术。时间反演后的声波或电磁波可自适应地匹配于传输信道,并有效地抑制甚至利用多径干涉,提高信息传输可靠性和探测精度。近年来该技术已成功地应用于目标探测、水声通信、无损检测、地震预报等方面,并成为电磁波领域中的一个研究热点。本文的研究围绕着基于时间反演的自适应聚焦天线阵列展开,研究了时间反演电磁波的空时聚焦特性以及与传播环境的相互作用机理,将其与阵列天线理论有机地结合起来,形成了基于时间反演的目标探测和波束形成算法,以及脉冲阵列天线的辐射分析设计方法。旨在为基于时间反演的阵列天线的研究、发展提供理论依据及新思路。首先,本文详细介绍了时间反演电磁波的聚焦原理,在此基础上建立了时间反演电磁波的实现模型和算法,并结合田口优化算法对影响聚焦效果的因素进行了讨论。从波动方程的时间反演对称性和电波传播的互易性出发,分别采用格林函数和多径信道模型分析了时间反演腔和时间反演镜操作下的时间反演电磁波的聚焦原理。并将时间反演操作算子引入时域有限差分法中,结合田口优化算法仿真分析了强散射环境下,时间反演镜单元位置、记录时间、记录波形、阵列配置等因素对时间反演聚焦脉冲峰值的影响。这些工作为时间反演自适应聚焦天线阵列的实现打下了基础。其次,对脉冲阵列天线的分析和设计方法进行了研究,并根据脉冲天线收发波形的时间反演特征,提出了一种收发模型可方便地对阵元间的互耦进行分析。脉冲阵列天线允许适当降低对天线单元的要求,配合高速度的开关可有效地提高系统辐射性能,并使其具有波束形成和波束扫描的能力,是实现自适应聚焦天线系统的一种有效的途径。由于脉冲阵列相关理论还处于发展阶段,其分析与设计存在着许多难点,因此论文提出了一些方法解决了部分问题。论文将点源分析方法和仿真计算相结合,提出了一种快速的脉冲阵列方向图的计算方法,极大地提高了计算速度减小了内存占用；还在时域推导了多路信号在空间实现最大化功率合成的条件,据此设计了一种阵馈抛物柱反射面天线,在轴向输出超宽带高功率的微波窄波束；另外,在超宽带系统传递函数的基础上,研究了脉冲天线在同一激励下的收发波形,发现了二者之间的时间反演特征；基于此提出了脉冲阵列天线系统的收发模型,用于分离阵元的辐射波形,实现互耦分析和阵列设计。一维TEM喇叭阵列的分析设计算例充分表明了该模型的正确性和有效性。然后,将时间反演技术与抛物方程法相结合实现了大气波导中辐射源的定位。波达方向估计是自适应波束形成的先决条件,然而在大气波导环境中,往往因多径效应造成接收信号畸变,导致常规的估计算法精度受到影响甚至无法工作。本文在仔细研究了抛物方程法和时间反演法的基本原理和实现算法的基础上,提出了在初始场上加载时间反演电磁波的方法,采用时间反演抛物方程法定位大气波导中的辐射源,仿真结果表明该方法和逆抛物方程法具有相同的定位精度。为了进一步提高该方法的实用性,又提出了将时间反演信息加载于反演阵列方向图的方法,在保证了相同定位精度的同时,将原天线阵元数量减少为十分之一。最后,将时间反演技术应用于波束形成算法当中,分别研究了近场的聚焦波束形成和远场的波束形成算法。在近场采用时间反演波补偿球面波的幅度和相位,实现了聚焦波束,并利用去自谱的聚焦算法得到了主波瓣更窄、旁瓣电平更低的波束。在远场利用时间反演对信号的自适应配对和聚焦能力,把接收信号的时反信息提取出来直接用作初始激励场的幅相参数,与迭代傅里叶变换法结合,优化了阵列激励的幅度,设计了超低旁瓣的多波束天线阵列。
[Abstract]:Time inversion is an adaptive space-time focusing technique. The acoustic wave or the electromagnetic wave after time inversion can be adaptively matched to the transmission channel, and the multi-path interference is effectively suppressed, and the reliability and the detection precision of the information transmission are improved. In recent years, the technology has been successfully applied to the aspects of target detection, underwater acoustic communication, non-destructive testing, earthquake prediction and so on, and has become a hot spot in the field of electromagnetic wave. In this paper, the time-inversion-based self-adaptive focusing antenna array is developed, and the time-to-time focusing characteristics of the electromagnetic wave and the interaction mechanism with the propagation environment are studied, and it is organically combined with the array antenna theory. The target detection and beam forming algorithm based on time inversion and the radiation analysis and design method of the pulse array antenna are formed. The purpose of this paper is to provide a theoretical basis and a new thought for the research and development of array antenna based on time inversion. Firstly, the focus principle of time-inversion electromagnetic wave is introduced in detail, and the realization model and algorithm of time-inversion electromagnetic wave are set up, and the factors that influence the focusing effect are discussed in combination with the field-opening optimization algorithm. Based on the time inversion symmetry of the wave equation and the reciprocity of the radio wave propagation, the focusing principle of the time inversion electromagnetic wave under the time inversion cavity and the time inversion mirror operation is analyzed by using the Green's function and the multi-path channel model, respectively. In this paper, the time inversion operation operator is introduced into the time domain finite difference method, and the influence of time inversion lens unit position, recording time, recording waveform, array configuration and other factors on the time inversion focusing pulse peak is analyzed by combining the field port optimization algorithm. These work lay a foundation for the time inversion of the adaptive focus antenna array. Secondly, the analysis and design method of the pulse array antenna is studied, and the mutual coupling between the elements can be conveniently analyzed based on the time inversion characteristics of the pulse antenna transmit/ receive waveform. The pulse-array antenna allows the proper reduction of the requirement of the antenna unit, and the high-speed switch can effectively improve the radiation performance of the system, and has the capability of beam forming and beam scanning, and is an effective way to realize the self-adaptive focusing antenna system. Because the theory of pulse array is still in the development stage, there are many difficulties in the analysis and design, so some methods have been put forward to solve some problems. By combining the point source analysis method and the simulation calculation, a rapid method for calculating the direction map of the pulse array is proposed, which greatly improves the calculation speed and reduces the memory occupation; and the condition that the multi-channel signal is used for maximizing the power synthesis in the space is also derived in the time domain, In addition, on the basis of the transfer function of the ultra-wideband system, the transmitting/ receiving waveform of the pulse antenna under the same excitation is studied, and the time inversion characteristics between them are found. The transmitting and receiving model of the pulse array antenna system is proposed, and the radiation waveform of the array element is separated, and the mutual coupling analysis and the array design are realized. The analysis and design of one-dimensional TEM horn array show the correctness and validity of the model. then, the time inversion technique and the parabolic equation method are combined to realize the positioning of the radiation source in the atmospheric waveguide. The DOA estimation is a prerequisite for adaptive beamforming, however, in the atmosphere waveguide environment, the distortion of the received signal is often caused by the multi-path effect, resulting in the accuracy of the conventional estimation algorithm being affected or even impossible to work. Based on a careful study of the basic principle and the implementation of the parabolic equation method and the time inversion method, a method for inverting the electromagnetic wave at the initial field loading time is proposed, and the radiation source in the atmospheric waveguide is positioned by the time inversion parabolic equation method, The simulation results show that the method and the inverse parabolic equation method have the same positioning accuracy. In order to further improve the practicability of the method, a method for loading the time inversion information in the inversion array direction map is proposed, and the number of the original antenna array elements is reduced to one-tenth while the same positioning accuracy is ensured. Finally, the time inversion technique is applied to the beam forming algorithm, and the beam forming and the beam forming algorithm of the near field are studied. In the near field, the time inversion wave is used to compensate the amplitude and phase of the spherical wave, the focus beam is realized, and the beam with lower main lobe and lower side lobe level is obtained by using the self-spectrum focusing algorithm. the self-adaptive pairing and focusing capability of the signal is inverted at the far field by using time, the time-inverse information of the received signal is extracted to be directly used as the amplitude phase parameter of the initial excitation field, combined with the iterative Fourier transformation method, the amplitude of the array excitation is optimized, An ultra-low sidelobe multi-beam antenna array is designed.
【学位授予单位】：西南交通大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN820.15

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