An Enhanced Extraction and Mitigation Scheme of Mutual RFI Between Spaceborne SARs Based on Pulse Compression

During the mission of spaceborne synthetic aperture radar (SAR), high resolution in range is obtained by transmitting signals with large bandwidth. As more and more SAR satellites are launched, spaceborne SARs sharing the same frequency band may generate mutual radio frequency interference (RFI) at orbital intersections. Due to its long duration, large bandwidth, and time-varying energy, mutual RFI (MRFI) will seriously deteriorate the quality of SAR images and pose severe challenges to interference mitigation. Based on the characteristics of MRFI, a high-precision enhanced interference extraction and mitigation scheme is proposed in this article. First, by combining the orbital prior information of SAR satellites with the time-frequency relationship of the interference signals, the MRFI pulses are compressed in range. Second, according to the characteristic that MRFI has time-varying energy in azimuth, the MRFI pulses are divided into two parts, namely, strong interference and weak interference. Based on the sparsity of SAR signal, sparse constraints are imposed on strong interference, and the strong MRFI is accurately separated by the robust principal component analysis (RPCA) method. For weak MRFI, the improved subspace projection method with better effect is used for reconstruction. Finally, MRFI is removed from the SAR signal to complete the mitigation. The experimental results based on simulated SAR data and measured spaceborne SAR data confirm the effectiveness and superiority of the proposed approach.