Study of Phase Error Reconstruction and Motion Compensation for Terahertz SAR with Sparsity-Promoting Parameter Estimation

In this article, a full aperture phase error reconstruction method upon the single range bin data is proposed based on the sparsity-promoting parameter estimation, for the effective motion compensation of synthetic aperture radar (SAR) in terahertz (THz) band. To improve the potential of the method for different forms of motion errors, the motion errors of the SAR platform are generally modeled as variant phase errors in each azimuth sampling points within the full aperture. A sensing matrix including the contribution of the phase errors is successfully derived to sparsely represent the SAR echo. After range compression, an iterative algorithm based on the single range bin data is developed to efficiently estimate the phase errors by updating the reflectivities of the dominant scatterers and the elements of the sensing matrix. Based on the reconstructed phase errors, the motion compensation can be successfully performed for the THz SAR to obtain the highly focused images. For the proof-of-principle experiments, a vehicle-borne SAR at 0.3-THz band with frequency modulation continuous wave transmitter and dechirp heterodyne receiver is developed. The simulation and the experimental results verify the effectiveness of the proposed method.