Azimuth Spectrum Reconstruction Algorithm Based on Updating Factors Regionally for Onboard Real-Time Multichannel SAR Imaging

Multichannel spaceborne synthetic aperture radar (SAR) is a useful approach to overcome minimum antenna area constraint and achieve high-resolution and wide-swath imaging. For multichannel SAR imaging, the azimuth ambiguity is the principal problem, which should be suppressed by azimuth spectrum reconstruction. However, the traditional azimuth spectrum reconstruction algorithm requires too large onboard resources to realize real-time imaging. To solve the problem, this article proposes a simplified azimuth spectrum reconstruction algorithm. By updating the factors regionally in azimuth, they only need to be calculated and stored once in each region. Hence, the onboard storage and computational resources can be effectively reduced. However, it will bring in the azimuth ambiguity to some extent, and further cause the spurious targets in the image. Fortunately, the deterioration of image quality is slight enough to be neglected if the region width (called focusing depth in this article) is properly chosen. Thus, this article also quantitatively analyzes the relationship between focusing depth and azimuth ambiguity, and further gives the focusing depth selection criterion to ensure that the spurious targets can be submerged in the clutter and noise. The results of computer simulations and real data experiment demonstrate the effectiveness of proposed algorithm.