基于改进wk算法的弹载SAR斜视成像

doi:10.3969/j.issn.1001-506X.2020.02.11

摘要/Abstract

摘要：

为提高弹载导引头成像精度,研究分析大斜视成像具有重大意义。针对传统wk算法在构造Stolt映射关系时未考虑等效速度变化以及进行方位校正时运算复杂等问题,提出基于改进wk算法的弹载合成孔径雷达斜视成像模型。首先,详细推导基于Stolt插值的wk算法,辨析在成像参数、多普勒中心校正和统一相位补偿等三个环节中易存在的混淆,为算法改进提供严谨模型。然后,针对非参考点目标的等效速度随着距离向不断变化,构造新的Stolt映射关系减小残余相位误差。在此基础上,针对较难精确实现多个点目标的方位位置校正函数,通过引入参考目标点构造近似校正函数,避免进行复杂的二维插值或坐标转换。最后,以大斜视成像为例,对多个点目标进行仿真,验证该算法的有效性。

关键词: 弹载合成孔径雷达, 斜视成像, wk算法

Abstract:

In order to improve the imaging accuracy of the missile-borne synthetic aperture radar based on circular scanning, it is of great significance to study and analyze the large squint imaging. Aiming at the problem that traditional wkalgorithm fails to take into account the change of equivalent velocity and the complexity of operation in carrying out azimuth correction when constructing Stoltmapping relation, an improved wkalgorithm for missile-borne SAR slant imaging model is proposed. First, wkalgorithm based on Stoltinterpolation is deduced in detail to identify the potential confusion in three links, namely, imaging parameters, correction of Doppler center and unified phase compensation, so as to provide a rigorous model for algorithm improvement. Then, a new Stoltmapping relation is constructed to reduce the residual phase error as the equivalent velocity of the non-reference point target changes with the distance. On this basis, in order to avoid complex 2-D interpolation or coordinate transformation, a reference target point is introduced to construct an approximate correction function. Finally, the effectiveness of the algorithm is verified by the simulation of multiple point targets with large squint imaging as an example.

Key words: missile-borne synthetic aperture radar, squint imaging, wk algorithm

中图分类号:

TN95

何耀民, 何华锋, 徐永壮, 苏敬, 王依繁. 基于改进wk算法的弹载SAR斜视成像[J]. 系统工程与电子技术, 2020, 42(2): 331-338.

Yaomin HE, Huafeng HE, Yongzhuang XU, Jing SU, Yifan WANG. Squint imaging of missile-borne SAR based on improved wk algorithm[J]. Systems Engineering and Electronics, 2020, 42(2): 331-338.

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变量	符号	表达式
距离向波数变量	K_R	4π(f₀+f_τ)/c
距离向中心波数	K_Rc	4πf₀/c
距离向基带波数	K_Rr	4πf_τ/c
方位向基带波数	K_A	2f_η/v

参数名称	正侧式成像	大斜视成像
波束中心穿越时刻	0	R₀tan(θ)/V
多普勒中心频率	0	2Vsin(θ)/λ
合成孔径时间	θ_BWR_c/V	θ_BWR_c/Vcos(θ)
方位向调频率	2V²/(λR_c)	2V²cos²(θ)/(λR_c)
多普勒带宽	2Vθ_BW/λ	$\frac{2 V \theta_{B W} \cos (\theta)}{\lambda}+\frac{2 V \sin (\theta) B_{r}}{c}$

距离向	方位向	反射系数	距离向	方位向	反射系数
R₀	X₀	1	R₀+100	X₀	1
R₀	X₀-100	1	R₀-200	X₀	1
R₀	X₀-200	1	R₀+250	X₀	1
R₀	X₀+100	1

成像参数	仿真数值	成像参数	仿真数值
发射信号频率/Hz	15.6×10⁹	斜视角/(°)	45
发射脉冲时宽/s	10×10^-6	水平速度/(m/s)	2 000
距离带宽/Hz	40×10⁶	水平加速度/(m/s²)	50
距离过采样率	1.2	垂直速度/(m/s)	-300
方位过采样率	1.25	垂直加速度/(m/s²)	-9.8
天线孔径/m	1.5	方位向宽度/m	220
距离向宽度/m	270

方向	峰值旁瓣比	积分旁瓣比	冲击响应宽度	像素值	图像分辨率
方位向	-18.62	-10.83	1.62	0.92	1.49
距离向	-13.46	-11.28	1.37	3.12	4.29