Polar format algorithm for the missile-borne spotlight SAR platform

High resolution SAR images are helpful for the missile seeker to select the key part of the target to enlarge damage effect. Though the motion of the radar platform is very complex in the terminal guidance phase, the geometric scene can be considered as the spotlight model because the antenna always points to the target. Different from the motion of the airborne platform, the velocity of the missile-borne platform in the range and the azimuth directions are non-uniform. Non-uniform linear motion not only leads to the range cell migration (MTRC), but also causes the rotation angle changes non-uniformly, resulting in imaging results defocused in the range and the azimuth directions. Through the analysis of the motion characteristics and the geometric scene of the missile-borne spotlight SAR, a PFA algorithm is derived under the condition of changing velocity. The MTRC caused by the radial motion is studied, and the impact of the motion compensation accuracy on the image quality is analyzed. Then the SINC interpolation is adopted to resolve the problem of the non-uniform azimuth angle caused by the changing-velocity cross motion. The simulation experiments get good focused SAR images, and verify the validity of the method.