基于子带信号处理的太赫兹SAR运动误差补偿方法

Motion error compensation method for terahertz SARbased on subband signal processing

摘要:

太赫兹合成孔径雷达（terahertz synthetic aperture radar，THz-SAR）波长短，可以工作在灰尘、雾霾等复杂战场环境。由于工作波长短，平台微小振动误差会使图像散焦严重。受高频振动误差的影响，目标除了自身响应外，沿方位向还会出现成对回波，给传统相位梯度自聚焦（phase gradient autofocus，PGA）算法强点提取和加窗操作增加了难度，影响运动误差提取精度。为了提高PGA算法精度，提出一种基于子带分解共轭消除相位误差的THz-SAR运动补偿方法，利用该概念可以重建出等效频率更低的SAR图像。由于相同运动误差对等效低频SAR图像影响大大降低，孤立强散射体散焦减弱，有利于强点提取和加窗。利用该图像结合PGA算法可实现运动误差信息的有效提取，并最终用于对原始THz-SAR图像的运动误差补偿。利用仿真数据和0.3 THz雷达实测数据进行了原理验证实验，结果验证了所提算法的有效性。

Abstract:

Terahertz synthetic aperture radar (THz-SAR) has a short wavelength. It can work in complex battlefield environments such as dust and haze. As the wavelength is much shorter, the tiny vibration of SAR platform will blur SAR images seriously. The high-frequency vibration error will result in paired echoes along the azimuth direction, which increases the difficulty of strong point extraction and windowing for the traditional phase gradient autofocus (PGA) algorithm. Correspondingly, the accuracy of motion error extraction will decrease. To improve the accuracy of PGA algorithm, in this paper, a motion compensation method for THz-SAR based on the conjugate cancellation of the phase errors with sub-band decomposition is proposed. With the proposed concept, an equivalent SAR image in a much lower frequency can be interestingly reconstructed. As the sensitivity upon the platform motion errors can be obviously reduced, the defocusing of the strong isolated scatterers can be greatly alleviated, which enables the effective extraction of their information for the motion compensation of the original THz-SAR image with PGA. The simulation data and the 0.3 THz radar measured data verify the effectiveness of the proposed algorithm.