FMCW SAR成像算法及实现

发布时间：2018-08-22 10:51

【摘要】：调频连续波合成孔径雷达(FMCW SAR)是结合了调频连续波技术和合成孔径技术的一种新型成像雷达体制,具有体积小、重量轻、功耗低、分辨率高等优点。又因为雷达成像过程中受外界诸如光线以及天气条件的影响比较小,再加上它的成本比较低廉、具有穿透成像能力,使得FMCW SAR能够广泛应用于民用领域进行环境监测、资源勘探、灾情救助等。高分辨率成像是FMCW SAR要解决的关键问题之一,因此,本课题在脉冲SAR的基础上,研究适用于FMCW SAR的高分辨率成像算法。本论文首先研究了合成孔径原理,获知保证方位向高分辨率的方法,然后研究了去调频原理,通过去调频处理一方面降低系统对采样率的要求,另一方面,经过去调频处理后的信号不再是线性调频信号,而是频率为常数的信号,这将极大地简化距离向的压缩过程;在此基础上,结合FMCW SAR系统几何模型,推导出了FMCW SAR体制下的回波模型。在原有的FMCW SAR距离多普勒(RD)成像算法基础上,加上对RVP项的处理,本论文提出了一种改进的正侧视模式下的RD算法,提高了成像分辨率;本论文还提出了一种适用于斜视模式下的FMCW SAR的距离多普勒算法;通过分析频率变标过程及其影响,对正侧视以及斜视模式下的频率变标(FS)算法分别提出了改进方法;最后本文还通过分析雷达载机偏离理想航迹所带来的影响,提出一种将运动补偿技术与成像算法相结合的算法来解决雷达非匀速直线运动下的高分辨成像问题。以上所提出的改进算法都通过实验仿真验证了其有效性。
[Abstract]:FM CW synthetic Aperture Radar (FMCW SAR) is a new imaging radar system which combines FM CW technology with synthetic aperture technology. It has the advantages of small volume, light weight, low power consumption and high resolution. Because the radar imaging process is less affected by external light and weather conditions, and because of its low cost and penetrating imaging ability, FMCW SAR can be widely used in the field of civil environmental monitoring. Resource exploration, disaster relief, etc. High resolution imaging is one of the key problems to be solved by FMCW SAR. Therefore, on the basis of pulsed SAR, a high resolution imaging algorithm suitable for FMCW SAR is studied in this paper. In this paper, the principle of synthetic aperture is studied firstly, and the method of ensuring azimuth high resolution is obtained. Then, the principle of de-frequency modulation is studied. On the one hand, the requirement of sampling rate is reduced by de-FM processing, on the other hand, the requirement of sampling rate is reduced. The signal processed by de-frequency modulation is no longer a linear frequency modulation signal, but a constant frequency signal, which greatly simplifies the compression process of the distance direction. On this basis, combined with the geometric model of the FMCW SAR system, The echo model under FMCW SAR system is derived. Based on the original FMCW SAR range Doppler (RD) imaging algorithm and the processing of the RVP term, this paper proposes an improved Rd algorithm in the positive side-looking mode, which improves the imaging resolution. This paper also proposes a range Doppler algorithm for FMCW SAR in strabismus mode. By analyzing the process of frequency scaling and its influence, this paper proposes some improved methods for the (FS) algorithm of frequency change in both strabismus mode and forward looking mode. Finally, by analyzing the influence of radar aircraft deviation from ideal track, an algorithm combining motion compensation technology with imaging algorithm is proposed to solve the problem of high resolution imaging under non-uniform linear motion of radar. The proposed improved algorithms are verified by experimental simulation.
【学位授予单位】：华侨大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN957.52

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