Off-Grid RFI Suppression Method in Synthetic Aperture Radar Based on Mismatch Reconstruction and Dictionary Rotation

In the process of radio frequency interference (RFI) suppression for synthetic aperture radar (SAR), when frequencies of RFIs are not located on discrete grids of the frequency spectrum, i.e., RFIs are off-grid, energies of RFIs will spread out, degrading suppression performances of lots of existing methods. To this end, aiming at the off-grid RFI suppression problem, in this article, a mismatch reconstruction and dictionary rotation-based RFI suppression method is proposed. First, using the defined support set, an optimization model is constructed to reconstruct mismatches of off-grid RFIs. Then, these mismatch variables are utilized to rotate the original Fourier transform-based dictionary so that frequencies of RFIs can be well matched. The energies of RFIs can be refocused under the representation of rotated dictionaries. At this time, we construct and solve another optimization problem to subtract RFIs and obtain the cleaned SAR signals. The real-world SAR data and simulated RFI data-based experiments demonstrate the effectiveness of the proposed method.