# Ground Moving Target Imaging for Highly Squint SAR by Modified Minimum Entropy Algorithm and Spectrum Rotation

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## Abstract

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## 1. Introduction

## 2. Signal Model

## 3. Proposed Method for Highly Squint SAR GMTIm

#### 3.1. MMEA for Parameter Estimation

#### 3.2. Spectrum Rotation for Geometry Correction

#### 3.3. Sparsity Enhancement for Sidelobe Suppression

## 4. Results

#### 4.1. GMTIm Based on Simulated Data

#### 4.2. GMTIm Based on GF-3 Data

## 5. Conclusions

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## Appendix A

## References

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**Figure 4.**(

**a**) Spectrum support region selection before the spectrum rotation; (

**b**) Spectrum support region selection after the spectrum rotation.

**Figure 10.**Moving target focused image and sparse enhancement image with or without spectrum rotation: (

**a**) Focused image without spectrum rotation; (

**b**) Focused image with SASR; (

**c**) Focused image with ESASR; (

**d**–

**f**) Sparse enhancement image of (

**a**–

**c**), respectively.

**Figure 11.**Point target response in azimuth and range profile of ESASR, ESASR-SE: (

**a**) Point target response in azimuth profile; (

**b**) Point target response in range profile.

**Figure 12.**Moving target focused image and sparse enhancement image with or without spectrum rotation: (

**a**) Focused image without spectrum rotation; (

**b**) Focused image with SASR; (

**c**) Focused image with ESASR; (

**d**–

**f**) Sparse enhancement image of (

**a**–

**c**), respectively.

**Figure 13.**(

**a**) Conventional RMA imaging results of ship target; (

**b**) The GMT parameter iteration graph of MMEA and IMEA.

**Figure 14.**Ship target refocusing process in Squint-looking SAR: (

**a**) Defocused ROI image; (

**b**) Focused image without spectrum rotation; (

**c**) Focused image with ESASR; (

**d**) Image of sparse enhancement.

PSNR(dB) | ISLR(dB) | ${\mathit{\theta}}_{\mathit{D}\mathit{A}}\left(\mathbf{rad}\right)$ | |
---|---|---|---|

Ideal value | −13.25 | −9.80 | 1.5708 |

MMEA | −13.01 | −9.56 | 0.9303 |

MMEA + SASR | −13.09 | −9.64 | 1.4366 |

MMEA + ESASR | −13.12 | −9.71 | 1.5307 |

60 Degrees | 75 Degrees | |
---|---|---|

Ideal value | 1.5708 | 1.5708 |

MMEA | 0.9132 | 0.8714 |

MMEA + SASR | 1.3652 | 1.3827 |

MMEA + ESASR | 1.5263 | 1.5174 |

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**MDPI and ACS Style**

Xiong, S.; Ni, J.; Zhang, Q.; Luo, Y.; Yu, L.
Ground Moving Target Imaging for Highly Squint SAR by Modified Minimum Entropy Algorithm and Spectrum Rotation. *Remote Sens.* **2021**, *13*, 4373.
https://doi.org/10.3390/rs13214373

**AMA Style**

Xiong S, Ni J, Zhang Q, Luo Y, Yu L.
Ground Moving Target Imaging for Highly Squint SAR by Modified Minimum Entropy Algorithm and Spectrum Rotation. *Remote Sensing*. 2021; 13(21):4373.
https://doi.org/10.3390/rs13214373

**Chicago/Turabian Style**

Xiong, Shichao, Jiacheng Ni, Qun Zhang, Ying Luo, and Longqiang Yu.
2021. "Ground Moving Target Imaging for Highly Squint SAR by Modified Minimum Entropy Algorithm and Spectrum Rotation" *Remote Sensing* 13, no. 21: 4373.
https://doi.org/10.3390/rs13214373