Detecting Maneuvering Weak Target with Doppler Spread Using Space-Air Bistatic FDA Radar

Compared with conventional monostatic radar systems, space-air bistatic frequency diverse array (FDA) radar exhibits superior anti-jamming capability and enhanced early-warning performance for weak and maneuvering targets. However, the complex bistatic configuration and the high velocity of spaceborne platforms introduce several challenges, including range migration (RM), Doppler spread (DS), and Doppler frequency migration (DFM). In particular, frequency offsets among FDA array elements exacerbate inter-channel Doppler mismatches, significantly reducing the coherent integration gain and consequently degrading detection performance. To address these issues, this article establishes a target echo model within a three-dimensional coordinate framework and provides an analysis of the different order terms. Subsequently, the SOKT is implemented to eliminate first- and second-order range migrations as well as the coupling induced by velocity ambiguity. Thereafter, the MDF is employed in the slow-time domain to compress Doppler spread and restore coherent gain. Simulation results verify that the SOKT-MDF approach effectively mitigates the effects of target velocity and acceleration, alleviates the Doppler spread (DS) problem, and significantly improves detection performance while maintaining low computational complexity.