A Novel 2-D Autofocusing Algorithm for Real Airborne Stripmap Terahertz Synthetic Aperture Radar Imaging

In practical applications, airborne terahertz synthetic aperture radar (THz-SAR) echo signal is not only affected by range amplitude and phase errors introduced by nonideal THz device but also affected by motion error in azimuth induced by the nonideal trajectory of platform, resulting in the 2-D defocus of image. To address the above errors, a novel 2-D autofocusing algorithm for real airborne stripmap THz-SAR imaging is proposed. In range autofocusing, the amplitude and phase errors are estimated simultaneously in range frequency domain based on the dominant point target selected in the preliminary focused images. To avoid dividing more subapertures in azimuth error estimate, the autofocusing method based on the maximization of image contrast is adopted. Then, range-Doppler algorithm (RDA) integrated with the proposed 2-D autofocusing is performed to obtain the focused images. The real measured data, acquired by a 0.22-THz airborne SAR system, are used to demonstrate the validity of the proposed algorithm. By comparing the imaging results, the proposed method can effectively and efficiently focus airborne stripmap THz-SAR images.