Multi-circular SAR Trajectory Design Based on Wavenumber Spectrum Analysis

Multi-circular SAR (MCSAR) maintains the transmitted signal beam still pointing to the same observing scene, and the platform continually watches around the scene many times in a general way, which can achieve the three-dimensional characteristics of the target for all directions and is the hotspot for CSAR imaging research. A reasonable flight path is the prerequisite of MCSAR imaging. In this article, the wavenumber spectrum and support domain of the MCSAR is derived from the echo signal model of the frequency-modulated continuous wave (FMCW) system. The characteristics of the MCSAR wavenumber spectrum support domain with a fixed radius, variable radius, and spiral trajectory are compared and analyzed through simulation. The results show that under the same flight space conditions, the wavenumber spectrum support domain varies from different trajectories. MCSAR with flight radius decreasing to flight height is the optimum trajectory. The wavenumber spectrum support domain of spiral trajectory is coiled, which is not suitable for the CSAR trajectory. They provide a theoretical basis to design the MCSAR trajectory.