临近空间SAR成像理论与成像方法研究
发布时间：2019-04-01 10:11
【摘要】：临近空间指距地球表面20公里至200公里高度的空域,其20公里至50公里的底部区域气压较低、扰流平稳、无云雨影响,适合浮空慢速平台等飞行器飞行。承载于临近空间慢速平台的合成孔径雷达(SAR)具有滞空时间长、重访周期短、观测地域广等优点,在敏感地区侦察和环境监测等领域具有重要的应用价值。临近空间慢速平台SAR具有许多不同于星载和机载雷达的特殊问题,需要探索研究,也是国际雷达界近年来研究的热点。本文针对临近空间慢速平台SAR的回波模型、成像模式、成像算法、运动补偿、动目标检测等核心问题进行了理论研究和数值仿真,主要内容如下:1、建立了临近空间慢速平台SAR的回波模型,分析了距离徙动、多普勒、距离方位耦合、空变等回波特性,为成像模式、成像算法的研究提供了理论依据。2、提出时分多视角共孔径成像模式,可有效利用慢速运动的冗余时间资源,对不同视角成像区域进行方位错位采样,为实现大场景快速成像提供了一种新的解决方案。3、提出基于非均匀傅里叶变换(NUFFT)的沿航向运动误差补偿方法,通过变标因子将时域非均匀样本在频域实现均匀化,可解决临近空间慢速平台沿航迹速度变化引起的成像主瓣展宽和旁瓣升高的问题。4、提出一种扩展波数域处理的成像算法,通过在波数域处理过程中嵌入对回波二维频谱的二维线性化和去空变处理,能够解决恒定加速度条件下临近空间慢速平台SAR成像区外侧的散焦和几何失真问题。5、研究了一种基于多普勒参数均衡+FrFT的运动目标成像方法,可利用距离徙动校正后静止与运动目标的回波多普勒调频率差异,分离动静目标回波,实现单通道斜视模式下临近空间慢速平台SAR的动目标成像。以上模型和算法的有效性均经过了仿真实验检验。结果表明,上述研究工作可用于实现临近空间慢速平台SAR的高效高精度成像。
[Abstract]:The adjacent space refers to the airspace between 20 km and 200 km from the earth's surface. The air pressure in the bottom region of 20 km to 50 km is relatively low, the disturbance current is stable, and the influence of cloud and rain is free, so it is suitable for flying aircraft such as floating-air slow-speed platform and so on. The synthetic Aperture Radar (SAR), which is carried on the slow platform near the space, has the advantages of long lag time, short revisit period and wide observation area. It has important application value in the fields of reconnaissance and environmental monitoring in sensitive areas. The near-space slow-speed platform SAR has many special problems which are different from spaceborne and airborne radar. It needs to be explored and studied, and it is also a hot research topic in the international radar field in recent years. In this paper, the echo model, imaging mode, imaging algorithm, motion compensation, moving target detection and other core problems of the near-space slow-speed platform SAR are studied theoretically and numerically. The main contents are as follows: 1, The echo model of the near space slow platform SAR is established, and the echo characteristics of range migration, Doppler, range azimuth coupling and space variation are analyzed, which provides the theoretical basis for the study of imaging mode and imaging algorithm. A time division multi-angle common aperture imaging model is proposed, which can effectively utilize the redundant time resources of slow motion to sample the azimuth dislocation of different angle imaging regions, which provides a new solution for fast imaging of large scenes. A compensation method of heading motion error based on non-uniform Fourier transform (NUFFT) is proposed in this paper. The non-uniform samples in time domain are homogenized in frequency domain by scaling factor. It can solve the problem of the widening of the main lobe and the rise of the sidelobe caused by the variation of the velocity along the track of the near-space slow-speed platform. 4. An imaging algorithm based on extended wavenumber domain processing is proposed. By embedding the two-dimensional linearization and devoid processing of the echo two-dimensional spectrum in the wavenumber domain processing, the problem of defocusing and geometric distortion on the outside of the SAR imaging region of the near-space slow-speed platform under the condition of constant acceleration can be solved. A moving target imaging method based on Doppler parameter equalization FrFT is studied in this paper. After range migration correction, the Doppler modulation frequency difference between static and moving targets can be used to separate the echoes of static and moving targets. The moving target imaging of the near space slow platform SAR in single channel squint mode is realized. The validity of the above models and algorithms has been verified by simulation experiments. The results show that the above-mentioned work can be used to realize the high-efficiency and high-precision imaging of the near-space slow-speed platform SAR.
【学位授予单位】：电子科技大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN957.52
，
本文编号：2451473
[Abstract]:The adjacent space refers to the airspace between 20 km and 200 km from the earth's surface. The air pressure in the bottom region of 20 km to 50 km is relatively low, the disturbance current is stable, and the influence of cloud and rain is free, so it is suitable for flying aircraft such as floating-air slow-speed platform and so on. The synthetic Aperture Radar (SAR), which is carried on the slow platform near the space, has the advantages of long lag time, short revisit period and wide observation area. It has important application value in the fields of reconnaissance and environmental monitoring in sensitive areas. The near-space slow-speed platform SAR has many special problems which are different from spaceborne and airborne radar. It needs to be explored and studied, and it is also a hot research topic in the international radar field in recent years. In this paper, the echo model, imaging mode, imaging algorithm, motion compensation, moving target detection and other core problems of the near-space slow-speed platform SAR are studied theoretically and numerically. The main contents are as follows: 1, The echo model of the near space slow platform SAR is established, and the echo characteristics of range migration, Doppler, range azimuth coupling and space variation are analyzed, which provides the theoretical basis for the study of imaging mode and imaging algorithm. A time division multi-angle common aperture imaging model is proposed, which can effectively utilize the redundant time resources of slow motion to sample the azimuth dislocation of different angle imaging regions, which provides a new solution for fast imaging of large scenes. A compensation method of heading motion error based on non-uniform Fourier transform (NUFFT) is proposed in this paper. The non-uniform samples in time domain are homogenized in frequency domain by scaling factor. It can solve the problem of the widening of the main lobe and the rise of the sidelobe caused by the variation of the velocity along the track of the near-space slow-speed platform. 4. An imaging algorithm based on extended wavenumber domain processing is proposed. By embedding the two-dimensional linearization and devoid processing of the echo two-dimensional spectrum in the wavenumber domain processing, the problem of defocusing and geometric distortion on the outside of the SAR imaging region of the near-space slow-speed platform under the condition of constant acceleration can be solved. A moving target imaging method based on Doppler parameter equalization FrFT is studied in this paper. After range migration correction, the Doppler modulation frequency difference between static and moving targets can be used to separate the echoes of static and moving targets. The moving target imaging of the near space slow platform SAR in single channel squint mode is realized. The validity of the above models and algorithms has been verified by simulation experiments. The results show that the above-mentioned work can be used to realize the high-efficiency and high-precision imaging of the near-space slow-speed platform SAR.
【学位授予单位】：电子科技大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN957.52
，
本文编号：2451473
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