Motion Compensation Imaging Algorithm of TeraHertz Synthetic Aperture Radar
ZHANG Qunying① JIANG Zhaofeng①② LI Chao① WU Shiyou① FANG Guangyou①
①(Key Laboratory of Electromagnetic Radiation and Detection Technology, Institute of Electronics,Chinese Academy of Sciences, Beijing 100190, China) ②(University of Chinese Academy of Sciences, Beijing 100049, China)
Theoretical analysis and engineering experience of SAR imaging shows that radar platform’s motion error will affect the quality of the image if its amplitude is greater than sub wavelength. Compared with traditional SAR working in microwave frequency band, TeraHertz SAR (THz-SAR) works in a shorter wavelength as the TeraHertz band, the control and measure accuracy of radar platform’s motion should be micron dimension, but the current technology can not meet the requirements. A novel motion compensation algorithm for THz-SAR imaging based on echo data is proposed in this paper. The attitude information from the inertial measurement unit is used to calibrate the migration error caused by the motion. Firstly, an obvious point like object is found in the coarse focusing image and the optimal position of this point is estimated by combining the antenna pattern and the maximum echo’s amplitude. Then the ideal echo of this point object is generated using the above estimated position and the phase error caused by the motion error of the platform is extracted by comparing the actual echo and the ideal echo. The extracted phase error is used to compensate the motion error of platform. The SAR system with center frequency 0.2 THz is used to carry out the outdoor vehicle experiment. Two dimensional high resolutions of SAR images of the corner reflectors and the metal strips are achieved. The validity of the proposed motion compensation algorithm is proved by experimental results.
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