A Robust Direct Path Interference Suppression Algorithm Based on Adaptive Component Extraction for GNSS-Based InBSAR System

Global navigation satellite system-based bistatic synthetic aperture radar interferometry (GNSS-based InBSAR) employs on-orbit navigation satellites as transmitters for interferometric processing. However, due to the use of C/A codes of navigation satellites, which do not decay in range direction after pulse compression, significant direct path interference (DPI) is introduced in SAR images. Moreover, the low power of navigation signals further complicates the suppression of DPI. In this letter, a robust DPI suppression algorithm based on adaptive component extraction is proposed for GNSS-based InBSAR. First, a signal model of the DPI is established, and a coarse reconstruction of the DPI is achieved through parameter estimation after azimuth accumulation. Subsequently, based on the reconstructed DPI, an adaptive extraction of the direct path component from the echo signal is performed to suppress the DPI while preserving the target echo. Using raw data from BeiDou satellites, the proposed algorithm improves the signal-to-interference ratio (SIR) from 8.27 to 16.11 dB and enhances the deformation accuracy of the interference area by 58.7%.