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DENG Kun, TIAN Xinran, YIN Chenxiao, et al. Fifth-order NCS algorithm for high-speed squint-forward-looking SAR imaging with low derivation complexity[J]. Journal of Radars, in press. doi: 10.12000/JR25187
Citation: DENG Kun, TIAN Xinran, YIN Chenxiao, et al. Fifth-order NCS algorithm for high-speed squint-forward-looking SAR imaging with low derivation complexity[J]. Journal of Radars, in press. doi: 10.12000/JR25187
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Fifth-order NCS Algorithm for High-speed Squint-forward-Looking SAR Imaging with Low Derivation Complexity

DOI: 10.12000/JR25187 CSTR: 32380.14.JR25187
  • 1.

    State Key Laboratory of Millimeter Waves, Southeast University, Nanjing 210096, China

  • 2.

    Purple Mountain Laboratory, Nanjing 211100, China

  • 3.

    Institute of Electromagnetic Space, Southeast University, Nanjing 210096, China

Funds:  The National Natural Science Foundation of China (62271142, U2341206), The Outstanding Youth Foundation of Jiangsu Province (BK20250070)
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    Abstract
  • High-speed squint-forward-looking Synthetic Aperture Radar (SAR) imaging (squint angle: >70°) is challenged by severe range-Doppler coupling and Doppler space variance. Traditional Nonlinear Chirp Scaling (NCS) algorithms can effectively mitigate Doppler space variance under high-squint conditions (squint angle: >30°), but they rely on approximate treatments and exhibit rapidly increasing derivation complexity at high scaling orders. This makes high-order generalization difficult and limits their application in high-speed squint-forward-looking SAR systems. To address this issue, this study demonstrates that Fourier Transform (FT) and Inverse FT (IFT) implementations, based on the principle of stationary phase and the method of series reversion for azimuth data domain transformation, exhibit regular structural patterns. Building on this insight, a fifth-order NCS algorithm with low derivation complexity is proposed, along with a dedicated geometric correction method. For a given predefined slant range model and NCS order, the proposed algorithm requires only a single FT/IFT derivation to obtain the analytical expression of the signal after NCS processing, thereby simplifying both the construction of the Doppler parameter linear equation system and the solution of NCS parameters. This significantly reduces the complexity of the algorithm derivation. Furthermore, an instantaneous projection geometric model is established based on the high-speed squint-forward-looking SAR imaging geometry, enabling the development of a tailored geometric correction method. Compared with traditional NCS algorithms, the proposed fifth-order NCS algorithm achieves superior imaging performance while maintaining computational efficiency. Simulated and real data processing validate its effectiveness and advantages in high-speed squint-forward-looking scenarios.

     

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