Improved Moving Target Imaging Method for a Multichannel HRWS SAR System

The azimuth multichannel synthetic aperture radar (AMC-SAR) system makes possible simultaneous high-resolution and wide-swath (HRWS) Earth observation. The motion of moving targets illuminated by the AMC-SAR system will not only lead to the failure of signal reconstruction, resulting in false targets in the image, but also to the defocusing of the moving targets. These problems can be effectively addressed by the estimation of the moving target parameters and their compensation in the signal. The existing imaging methods focus on eliminating the impact of radial velocity on signal reconstruction and disregard the influence of other motion parameters. However, the radial acceleration, azimuth acceleration, and azimuth velocity of moving targets affect the accuracy of the signal reconstruction and focusing of the images. To eliminate the influence of target motion, this letter proposes a moving target imaging method. First, the proposed method transforms the problem of parameter estimation into the problem of phase error estimation. Second, the quadratic phase error (QPE) is accurately estimated via autofocus theory and compensated in the signal, improving the focusing of a moving target. Then, the linear phase error (LPE) is accurately estimated via subspace theory and compensated in the signal, improving the accuracy of signal reconstruction. The effectiveness of our proposed method is demonstrated through processing of simulated SAR data.