星载高分辨频率步进SAR成像技术

龙腾; 丁泽刚; 肖枫; 王岩; 李喆

doi:10.12000/JR19076

星载高分辨频率步进SAR成像技术

DOI: 10.12000/JR19076

北京理工大学信息与电子学院雷达技术研究所北京 100081
北京理工大学嵌入式实时信息处理技术北京市重点实验室北京 100081

基金项目: 国家杰出青年科学基金(61625103)，国家自然科学基金(11833001)

详细信息

作者简介:
龙　腾(1968–)，男，湖北黄陂人。北京理工大学教授、博士生导师。现任北京理工大学副校长、雷达技术研究所所长。研究方向为新体制雷达与实时信息处理。E-mail: longteng@bit.edu.cn

丁泽刚(1980–)，男，河南信阳人，博士。现担任北京理工大学研究员、博士生导师，主要研究方向为新体制雷达成像机理、成像处理和图像信息提取。E-mail: z.ding@bit.edu.cn

肖　枫(1993–)，男，内蒙古包头人。北京理工大学雷达技术研究所在读博士研究生，主要研究领域为多模式星载SAR成像技术、SAR运动补偿技术。E-mail: 1120646612@qq.com

王　岩(1989–)，男，河北沧州人。博士后，现担任北京理工大学副研究员、硕士生导师，主要研究方向为新体制雷达系统、成像、干涉和极化应用。E-mail: yan_wang@bit.edu.cn

李　喆(1996–)，男，河北任丘人。北京理工大学信息与电子学院硕士研究生，主要研究方向星载合成孔径雷达系统设计与成像。E-mail: 3120180770@bit.edu.cn

通讯作者:
龙腾 longteng@bit.edu.cn

丁泽刚 z.ding@bit.edu.cn

中图分类号: TN958
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出版历程
- 收稿日期: 2019-08-30
- 修回日期: 2019-12-01
- 网络出版日期: 2019-12-01

Spaceborne High-resolution Stepped-frequency SAR Imaging Technology

Radar Research Lab, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
Beijing Key Laboratory of Embedded Real-Time Processing Technology, Beijing 100081, China

Funds: The National Science Foundation for Distinguished Young Scholars (61625103), The National Natural Science Foundation of China (11833001)

More Information

Corresponding author: LONG Teng, longteng@bit.edu.cn; DING Zegang, z.ding@bit.edu.cn

摘要

摘要: 星载合成孔径雷达(SAR)是一种2维高分辨率微波成像雷达。它通过发射大带宽信号实现距离向高分辨，通过合成孔径技术实现方位向高分辨。随着人们对分辨率需求的不断提升，星载SAR正朝着分米级分辨率发展。一方面，受限于现有器件水平，可以通过频率步进技术实现大带宽信号发射，需要研究高精度子带拼接技术、子带间幅相误差对成像的影响与补偿技术；另一方面，受限于有限的波束宽度，可以使系统工作在聚束模式或滑聚模式实现长合成孔径，此时需研究轨道弯曲、“Stop-go”假设误差、电离层与对流层传输误差等非理想因素对成像的影响与补偿技术。因此，该文详细介绍了频率步进信号时序设计与子带拼接，研究星载高分辨率频率步进SAR成像算法与非理想因素补偿方法，最后给出成像算法的仿真验证和性能分析。
- 频率步进 /
- 高分辨成像 /
- 滑动聚束
Abstract: Spaceborne Synthetic Aperture Radar (SAR) is a type of microwave imaging radar with 2D high resolution. This technological device achieves range high resolution by transmitting wideband signals and azimuth high resolution through the synthetic aperture approach. With the increasing demand for high-resolution imaging, the resolution of spaceborne SAR has moved toward the decimeter level. On the one hand, limited by the present hardware technology, achieving wideband signal transmission through stepped-frequency technology is necessary. In this case, we need to study high-precision bandwidth synthesis technology. The influence of slant range error and amplitude and phase error between sub-bands should be considered. On the other hand, due to limited beamwidth, the system needs to work in sliding spot mode to achieve a long synthetic aperture. In this case, we need to study the problem of imaging parameter variance caused by curved orbit, “Stop–go” error, and the influence of ionospheric and tropospheric transmission errors on imaging. To solve these problems, this paper introduces the principle of stepped-frequency signal design and bandwidth synthesis technology in detail. A time-domain algorithm and non-ideal factor compensation method are proposed for spaceborne high-resolution stepped-frequency SAR imaging. Finally, simulation verification and performance analysis of the imaging algorithm are conducted.
- Stepped frequency /
- High-resolution imaging /
- Sliding-spotlight

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图 1 子带并发

Figure 1. Simultaneously transmitted subpulses

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图 2 脉内子带串发

Figure 2. Sequential subpulses transmitted in PRT

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图 3 脉间子带串发

Figure 3. Sequential subpulses transmitted interpulse

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图 4 高分辨率星载SAR子带交替串发设计结果

Figure 4. Design result of subpulses transmitted alternatively for high resolution spaceborne SAR

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图 5 轨道弯曲引起的等效速度空变

Figure 5. Equivalent speed variance caused by curved orbit

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图 6 “Stop-go”误差引起的方位向偏移

Figure 6. Azimuth migration caused by stop-go error

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图 7 星载高分辨率SAR 100 s工作期间典型折射率下斜距误差的变化图

Figure 7. Range error variance of spaceborne high resolution SAR in typical refractive index during 100 s operation

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图 8 电离层导致的二次相位误差

Figure 8. Quadratic phase error caused by ionosphere error

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图 9 高分辨率滑动聚束星载SAR成像算法总流程

Figure 9. Flow chart of high resolution sliding spotlight spaceborne SAR imaging algorithm

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图 10 信号子带拼接前后对比

Figure 10. Stepped frequency subband signal and simulation result of synthetic bandwidth

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图 11 加入幅相误差的子带拼接结果

Figure 11. Compressed synthetic signal with amplitude errors and phase errors

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图 12 加入对流层误差的成像结果

Figure 12. Imaging result with troposphere error

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图 13 加入不同电离层误差的成像结果

Figure 13. Imaging results with different ionosphere errors

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图 14 加入不同大小DEM误差的成像结果

Figure 14. Imaging results with different DEM errors

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图 15 高分辨率滑动聚束星载SAR点阵目标成像结果图

Figure 15. Imaging result of dot targets with high resolution sliding spotlight spaceborne SAR

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表 1 高分辨率宽测绘带滑动聚束典型参数

Table 1. Typical parameters for sliding spotlight SAR with high resolution and wide swath

参数	数值
距离向发射带宽	2.4 G，单个脉冲400 M
PRF	3000～4000 Hz，分段变重频
采样延迟	分段变采样延迟
聚束因子	1/40

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表 2 典型大气参数

Table 2. Typical atmosphere parameters

参数	数值
场景大气压	1.014 MPa
相对湿度	20%
场景气温	10°C
场景海拔	100 m

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表 3 高分辨滑动聚束成像评估结果

Table 3. Evaluation results of high resolution sliding spotlight imaging

点目标	距离向		方位向		距离向分辨率 (m)	方位向分辨率 (m)
点目标	PSLR (dB)	ISLR (dB)	PSLR (dB)	ISLR (dB)	距离向分辨率 (m)	方位向分辨率 (m)
a	–25.72	–19.46	–23.13	–18.22	0.15	0.16
b	–25.42	–19.46	–22.97	–19.01	0.15	0.16
c	–25.70	–19.45	–24.76	–19.59	0.15	0.16
d	–25.66	–19.49	–21.77	–18.69	0.15	0.16
e	–25.37	–19.23	–21.27	–18.43	0.15	0.16

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