Range-Velocity Imaging of Migrating Targets With Velocity Ambiguity via Modified Iterative Adaptive Filtering

During the imaging time, range migration (RM), velocity ambiguity, and range-velocity sidelobes may occur for multiple closely-spaced moving targets, which may result in image smeared. To mitigate the impact of these factors on image focusing, this paper proposes a modified iterative adaptive filtering method based on coherent integration outputs. It first employs Keystone transform with each possible velocity ambiguity number to correct RM and applies fast Fourier transform-based integration to focus target energy within the mainlobe. Subsequently, the coherent integration outputs are divided into distinct processing windows. The data within each processing window are sequentially employed as inputs for the modified iterative adaptive filtering to effectively suppress sidelobes including blind speed sidelobes and retrieve targets with low computational complexity. The adoption of a threshold criterion and the exploitation of covariance matrix structure facilitate a further reduction in computational complexity. Both simulation and experiment results validate the performance of the proposed method.