A Method for Recovering the Coherence of the Dechirp Received Echo From Space Targets for Space-borne ISAR and Its Rapid Implementation Technology Based on FPGA
Inverse synthetic aperture radar(ISAR)has two-dimensional high-resolution imaging capability and can achieve high-precision detection and monitoring of space targets.Compared with ground-based ISAR,space-borne ISAR can detect and image space targets in a larger range and is more flexible,which provides favorable support for space situational awareness.Dechirp re-ceiving system can greatly reduce the sampling rate and lighten the hardware burden of the system;hence,this system is usually a-dopted by spaceborne ISAR.However,during the observation time,the range of the space target relative to the space-borne ISAR varies greatly,so the radar needs to constantly change the wave gate to ensure stable tracking of high-speed targets in space,which seriously undermines the coherence of radar echoes.At the same time,the decrease in the accuracy of motion compensation is brought about by the complex motion geometry of high-speed targets relative to space-borne ISAR.To solve this problem,a method for dechirp receiving coherence recovery of space-borne ISAR for space targets is proposed in this paper,which can effectively re-cover echo coherence with different range wave gates on a pulse-by-pulse basis,and the estimated parameters are used to accurately compensate for motion.Based on this method,a fast implementation scheme for dechirp receiving coherence recovery based on FP-GA was designed.Simulation experiments verify the effectiveness of the proposed method and its FPGA implementation scheme.