Geometry-Enhanced Interference Localization in Bistatic SAR via Virtual Baseline Construction

Bistatic synthetic aperture radar (SAR) provides multidimensional Earth observation capability, but radio frequency interference (RFI) can degrade SAR image quality and bistatic interferometric coherence. Compared with monostatic SAR, bistatic SAR provides additional spatial information that can be exploited to infer the position of RFI sources. This article provides the first demonstration and assessment of geometric degeneracy in bistatic SAR configuration and proposes an RFI localization method via virtual-baseline construction on measured bistatic RFI data. First, the bistatic propagation geometry is explicitly modeled, and a hyperbolic intersection localization model is established. The geometric degeneracy mechanism is explained through the derivation and analysis of the geometric dilution of precision (GDOP). Second, a virtual-baseline construction method is introduced to synthesize new observation geometries by pairing RFI pulses across different time indices. Furthermore, an optimal baseline-pair selection strategy based on GDOP assessment is proposed to further improve localization accuracy while mitigating geometric degeneracy. Finally, the effectiveness of the proposed method is verified using Monte Carlo simulations and measured bistatic SAR data. The results demonstrate the feasibility of RFI localization in bistatic SAR and show that the proposed virtual-baseline strategy improves localization accuracy from 20 km to a tens-of-meter level.