Performance Investigation on Elevation Cascaded Digital Beamforming for Multidimensional Waveform Encoding SAR Imaging

HE Feng ZHANG Yongsheng SUN Zaoyu JIN Guanghu DONG Zhen

何峰, 张永胜, 孙造宇, 等. 多维波形编码SAR俯仰向级联DBF成像性能分析[J]. 雷达学报, 2020, 9(5): 828–855. DOI: 10.12000/JR20107
引用本文: 何峰, 张永胜, 孙造宇, 等. 多维波形编码SAR俯仰向级联DBF成像性能分析[J]. 雷达学报, 2020, 9(5): 828–855. DOI: 10.12000/JR20107
HE Feng, ZHANG Yongsheng, SUN Zaoyu, et al. Performance investigation on elevation cascaded digital beamforming for multidimensional waveform encoding SAR imaging[J]. Journal of Radars, 2020, 9(5): 828–855. DOI: 10.12000/JR20107
Citation: HE Feng, ZHANG Yongsheng, SUN Zaoyu, et al. Performance investigation on elevation cascaded digital beamforming for multidimensional waveform encoding SAR imaging[J]. Journal of Radars, 2020, 9(5): 828–855. DOI: 10.12000/JR20107

Performance Investigation on Elevation Cascaded Digital Beamforming for Multidimensional Waveform Encoding SAR Imaging

doi: 10.12000/JR20107
Funds: The National Natural Science Foundation of China (61771478)
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    Author Bio:

    HE Feng received the B.S. and Ph.D. degrees in signal processing from National University of Defense Technology, Changsha, in 1998 and 2005, respectively. From March 2015 to September 2015, he joined the scientific staff of the Technical University of Munich to work within a cooperation framework at the Microwaves and Radar Institute, German Aerospace Center (DLR), Wessling, Germany. Here as a visiting scholar, he participated in the distributed spaceborne SAR research work. He is currently a professor with the College of Electronic Science and Technology, National University of Defense Technology. His current major research interests include SAR processing, array processing, and MIMO radar system. E-mail: hefeng@nudt.edu.cn

    ZHANG Yongsheng was born in Inner Mongolia, China, in December 1977. He received the Ph.D. degrees in electronics and information engineering from National University of Defense Technology in 2007. He is currently a professor with the College of Electronic Science and Technology, National University of Defense Technology. His current major research interests include SAR system design and SAR data processing. E-mail: zhangyongsheng@nudt.edu.cn

    SUN Zaoyu was born in Hubei, China, in July 1978. He received the B.S. and Ph.D. degrees in signal processing from National University of Defense Technology, Changsha, in 2000 and 2008, respectively. He is currently a lecturer with the College of Electronic Science and Technology, National University of Defense Technology. His research interests include SAR and InSAR processing. E-mail: sunzaoyu@nudt.edu.cn

    JIN Guanghu was born in Anhui, China, in February 1980. He received the B.E., M.S. and Ph.D. degrees in signal processing from National University of Defense Technology, Changsha, in 2002, 2004 and 2009 respectively. He is currently an associate professor with the College of Electronic Science and Technology, National University of Defense Technology. His research interests include Synthetic Aperture Radar (SAR), inverse SAR, and radar target recognition. E-mail: guanghujin@nudt.edu.cn

    DONG Zhen was born in Anhui, China, in September 1973. He received the Ph.D. degree in electrical engineering from National University of Defense Technology, Changsha in 2001. He is currently a professor with the College of Electronic Science and Technology, National University of Defense Technology. His recent research interests include SAR system design and processing, Ground Moving Target Indication (GMTI), and digital beamforming. E-mail: dongzhen@nudt.edu.cn

    Corresponding author: He Feng, hefeng@nudt.edu.cnDong Zhen, dongzhen@nudt.edu.cn
  • 摘要: 在采用多维波形编码(MWE)技术的新体制合成孔径雷达(SAR)系统中,利用俯仰向的数字波束形成(DBF)来实现多个发射波形重叠回波的可靠分离是一个关键问题。该文详细研究了星上实时波束控制与地面后置零陷控制相结合的混合俯仰向DBF分离方法的成像性能问题。 作为一种包括星地两级DBF网络的级联结构,其中的星上部分通过在划分的多个天线子孔径上实现实时主瓣波束指向控制,确保在整个测绘上足够的信号接收增益; 而后置自适应DBF网络主要完成零陷抑制的任务,以消除其它发射波形带来的距离向干扰,可自适应于地形高度起伏变化带来的视角变化。根据对发射波形时频结构先验信息的利用情况,提出了两种星上实时波束形成器的实现方式。对混合DBF方法下的成像信噪比和模糊度性能进行了理论建模与仿真实验评估。实验结果表明,混合DBF方法可以为优化图像模糊度和信噪比性能提供额外的设计自由度,并降低星上数据通道数目。与纯地面DBF网络相比,采用混合DBF网络可以在显著减少星上输出数据量的同时获得满意的性能,在给出的实例中,实现相近性能的条件下,相应的星上数据通道数从10个减少到6个。

     

  • Figure  1.  Azimuth MWE on transmit

    Figure  2.  Azimuth MWE on receive

    Figure  3.  Cascaded DBF networks in elevation performing the SNR-preserving and interferences-free signal separation

    Figure  4.  Number of real multiplications per second of the proposed two types of onboard DBF processing and the reference beamforming processing given in Ref. [8] (N=5 and P= 8)

    Figure  5.  The array patterns of onboard Type-A beamforming at instantaneous time $t = {\tau _{\rm{c}}}$

    Figure  6.  Amplitude of the distortion functions $\mu _m^{(0)}(t)$ in the extent of each of 4 subpulses

    Figure  7.  Performance comparison on RASR between the cascaded hybrid Type-A DBF networks and ground DBF in Ref. [8]

    Figure  8.  Performance comparison on SNR between the cascaded hybrid Type-A DBF networks and ground DBF in Ref. [8]

    Figure  9.  The array patterns of onboard Type-B beamforming at instantaneous time $t = {\tau _{\rm{c}}}$

    Figure  10.  Performance comparison on RASR between the cascaded hybrid Type-B DBF networks and ground DBF in Ref. [8]

    Figure  11.  Performance comparison on SNR between the cascaded hybrid Type-B DBF networks and ground DBF in Ref. [8]

    Figure  12.  Across comparison of performance on RASR and SNR between the onboard transmit signal-structure-dependent beamformers (Type-B) and the non-signal-dependent ones (Type-A)

    Figure  13.  Performance on RASR and SNR for Type-A and Type-B SNR-preferred beamformers with an increased element spacing

    Figure  14.  Performance on RASR and SNR of the cascaded DBF networks under the DOA mismatch condition in the presence of topographic height error, in comparison with the onboard real-time null-steering DBF in Ref. [7]

    Table  1.   Parameters used in the system simulation[8]

    ParameterValueParameterValue
    Wave length0.031 mNumber of subpulses4
    Swath width100 kmPRF1310 Hz
    Off-nadir angle18o~24oAzimuth subapertures4
    Azimuth resolution1.5 mAntenna length10.8 m
    Band width250 MHzAntenna height2.33 m
    Ground range resolution at center1.5 mProcessed Doppler bandwidth4890 Hz
    Onboard elevation channel number6Azimuth ambiguity to signal ratio–30 dB
    Orbital altitude800 kmSubpulse duration/ interval40 μs
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出版历程
  • 收稿日期:  2020-07-23
  • 修回日期:  2020-09-28
  • 网络出版日期:  2020-10-28

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