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.
