基于谱压缩的大斜视TOPS BP图像自聚焦算法

doi:10.19665/j.issn1001-2400.20230102

摘要/Abstract

摘要：

在机动平台大斜视TOPS模式SAR成像时,通过使用地平面直角坐标系BP成像算法,能够在短时间内获取地距平面无畸变的宽幅SAR图像,但实际应用中如何对BP图像快速完成运动误差补偿与旁瓣抑制仍是一个难点。针对此问题,提出了一种改进的谱压缩方法,基于此能够快速实现机动平台大斜视TOPS模式地平面BP图像自聚焦等后续操作。首先,考虑到传统BP谱压缩方法仅适用于聚束成像模式,结合大斜视TOPS SAR虚拟旋转中心理论与波数谱分析,推导出了改进的精确谱压缩函数,能够通过全孔径压缩获得无模糊的地平面TOPS模式BP图像频谱。在此基础上,利用相位梯度自聚焦(PGA)能够快速完成全孔径运动误差估计与补偿。此外,基于提出的改进谱压缩方法得到的无模糊对齐BP图像频谱,可以在方位频域统一加窗实现图像旁瓣抑制。最后,通过仿真数据处理验证了所提算法的有效性。

关键词: TOPS模式, 地平面BP成像, 谱压缩, 运动误差补偿, 旁瓣抑制

Abstract:

In the high squint TOPS mode SAR imaging of the maneuvering platform,by using the BP imaging algorithm in the rectangular coordinate system of the ground plane,the wide swath SAR image without distortion in the ground plane can be obtained in a short time.However,how to quickly complete the motion error compensation and side lobe suppression of the BP image is still difficult in practical application.This paper proposes an improved spectral compression method,which can quickly realize the follow-up operations such as autofocus of the BP image of the ground plane in the high squint TOPS mode of the mobile platform.First,by considering that the traditional BP spectral compression method is only applicable to the spotlight imaging mode,combined with the virtual rotation center theory of high-squint TOPS SAR and the wavenumber spectrum analysis,an improved exact spectral compression function is derived,which can give rise to the unambiguous ground plane TOPS mode BP image spectrum through full-aperture compression,on the basis of which the phase gradient autofocus(PGA) can be used to quickly complete the full aperture motion error estimation and compensation.In addition,based on the unambiguous aligned BP image spectrum obtained by the improved spectral compression method proposed in this paper,the image sidelobe suppression can be realized by uniformly windowing in the azimuth frequency domain.Finally,the effectiveness of the proposed algorithm is verified by simulation data processing.

Key words: TOPS mode, ground rectangular coordinate BP imaging, spectrum compression, motion error compensation, sidelobe suppression

中图分类号:

TN958

周生威, 李宁, 邢孟道. 基于谱压缩的大斜视TOPS BP图像自聚焦算法[J]. 西安电子科技大学学报, 2024, 51(1): 1-10.

ZHOU Shengwei, LI Ning, XING Mengdao. Spectrum compression based autofocus algorithm for the TOPS BP image[J]. Journal of Xidian University, 2024, 51(1): 1-10.

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参数	数值	参数	数值
合成孔径时间/s	0.2	带宽/MHz	160
载频/GHz	16.9	速度/(m·s^-1)	(550,-120,0)
PRF/kHz	16	方位中心时刻斜视角/(°)	65
脉宽/μs	10	高度/km	9.8
波束宽度/(°)	4	波束扫描速度/((°)·s^-1)	180

		自聚焦与加窗前	所提算法自聚焦与加窗后
距离向	PSLR	-10.170 3	-27.964 9
	ISLR	-8.202 9	-26.303 0
方位向	PSLR	-1.379 2	-25.738 8
	ISLR	-2.047 6	-22.546 2