A modified SPECAN algorithm based on Chirp Scaling principle

When synthetic aperture radar (SAR) works at the squint mode with a large grazing angle, the range walk varies obviously with the slant range. The traditional SPECAN algorithm corrects the range walk only based on the central slant range. Thus there are residual range walks at range edges of the swath, which finally leads to the defocus of the image. In order to solve this problem, a modified SPECAN algorithm based on the Chirp Scaling principle is proposed in this paper. First, the received data is multiplied by Chirp Scaling factor in the two-dimension time domain to eliminate the range variation of the range walk. Then the traditional SPECAN algorithm is applied to accomplish the two-dimension focus of the image. Simulation results confirm the validity of the proposed algorithm.