多天线合成孔径雷达成像研究

发布时间：2018-10-08 09:17

【摘要】：作为一种高分辨成像雷达技术,合成孔径雷达(Synthetic Aperture Radar,SAR)在军事侦察、遥感观测等领域发挥了重要的作用。然而,单个发射和接收天线的常规SAR系统不能满足对空间分辨率和测绘带宽度日益增长的需求。多天线技术(Multiple-Input Multiple-Output,MIMO)与SAR技术相结合,利用波形分集和天线分集,可以获得远多于单个天线的空间自由度,从而实现高分辨率宽测绘带成像,渐渐成为了人们的研究热点。鉴于此,本文以SAR成像处理方法为基础,研究MIMO-SAR雷达的正交发射波形以及MIMO-SAR成像的基本处理方法。本文具体研究内容如下:(1)MIMO-SAR雷达正交发射波形设计。依据雷达发射信号正交性原理,本文研究了采用OFDM(Orthogonal Frequency Division Multiplexing)调制技术的正交波形集。首先,研究了子载波采用线性调频(Linear Frequency Modulation,LFM)信号的正交信号,对其自相关、互相关和模糊函数特性进行了仿真分析。其次,研究了相位编码(Phase Coded,PC)OFDM信号的正交性。采用混沌映射序列来产生新型的相位编码信号,该类信号具有保密性强、低截获的优点。针对混沌PC-OFDM信号的自相关性、互相关性、模糊函数以及多普勒容忍性展开仿真分析,并且讨论了该类信号的优缺点。(2)传统单天线SAR成像方法研究。首先,分析SAR成像原理以及建立SAR信号回波模型。其次,采用距离-多普勒(Range-Doppler,R-D)算法进行成像仿真研究,并利用RADARSAT-1雷达数据验证R-D算法的有效性。最后,针对稀疏场景的SAR成像,采用压缩感知理论对SAR点目标回波信号聚焦成像,实验表明压缩感知在SAR成像旁瓣抑制方面有很大优势。(3)多天线SAR成像处理方法的研究。首先,分析常规SAR最小天线面积限制,建立三发三收基于OFDM-LFM正交信号的MIMO-SAR成像模型。其次,结合距离向高分辨的要求,对回波信号采用子带拼接的方法在距离向合成大带宽信号。最后,针对SAR方位向高分辨与宽测绘带的要求,采用低脉冲重复频率发射雷达信号,在方位向利用多通道重建法,消除频谱混叠。实验仿真验证该方法的有效性,与常规SAR成像算法的聚焦图像进行对比,表明MIMOSAR能够实现高分辨宽测绘带成像。
[Abstract]:As a high resolution imaging radar technology, synthetic Aperture Radar (Synthetic Aperture Radar,SAR) plays an important role in military reconnaissance, remote sensing observation and other fields. However, conventional SAR systems with single transmitting and receiving antennas cannot meet the increasing demand for spatial resolution and the width of mapping bands. Combining multi-antenna technology (Multiple-Input Multiple-Output,MIMO) with SAR technology, using waveform diversity and antenna diversity, the spatial degree of freedom can be obtained much more than a single antenna, thus the high resolution and wide mapping band imaging has gradually become a hot research topic. In view of this, based on the SAR imaging processing method, the orthogonal transmitting waveform of MIMO-SAR radar and the basic processing method of MIMO-SAR imaging are studied in this paper. The main contents of this paper are as follows: (1) MIMO-SAR radar orthogonal waveform design. Based on the principle of orthogonality of radar transmitted signals, the orthogonal waveform set using OFDM (Orthogonal Frequency Division Multiplexing) modulation technique is studied in this paper. Firstly, the orthogonal signals with linear frequency modulated (Linear Frequency Modulation,LFM) subcarriers are studied, and the characteristics of autocorrelation, cross-correlation and ambiguity function are simulated and analyzed. Secondly, the orthogonality of phase coded (Phase Coded,PC) OFDM signal is studied. Chaotic mapping sequences are used to generate new phase coded signals, which have the advantages of high security and low interception. The self-correlation, cross-correlation, ambiguity function and Doppler tolerance of chaotic PC-OFDM signals are simulated, and the advantages and disadvantages of these signals are discussed. (2) the traditional single-antenna SAR imaging method is studied. Firstly, the principle of SAR imaging and the echo model of SAR signal are analyzed. Secondly, the range Doppler (Range-Doppler,R-D) algorithm is used for imaging simulation, and RADARSAT-1 radar data are used to verify the validity of R-D algorithm. Finally, for sparse SAR imaging, compression sensing theory is used to focus SAR point target echo signal. Experiments show that compression sensing has a great advantage in sidelobe suppression of SAR imaging. (3) Multi-antenna SAR imaging processing method is studied. Firstly, the limit of minimum antenna area of conventional SAR is analyzed, and a MIMO-SAR imaging model based on OFDM-LFM orthogonal signal is established. Secondly, according to the requirement of high resolution in range direction, the echo signal is synthesized with large bandwidth signal in range direction by subband splicing. Finally, according to the requirement of SAR azimuth high resolution and wide mapping band, low pulse repetition frequency is used to transmit radar signal, and multi-channel reconstruction method is used in azimuth direction to eliminate spectrum aliasing. The experimental results show that the proposed method is effective and compared with the focus image of conventional SAR imaging algorithm. It shows that MIMOSAR can achieve high resolution and wide mapping band imaging.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN958

【参考文献】