Harmonic-Assisted TDOA Localization Method for Saturation Interference Sources in SAR Satellite Systems

Accurate localization of spaceborne Synthetic Aperture Radar (SAR) interference sources facilitates the search, identification, and characterization of interferers, while also providing prior information for enhancing interference suppression, making it a current research focus. For locating the most common ground-based co-frequency radar interferers in SAR satellite systems, several methods have been developed by exploiting the spatial variation of periodic pulse arrival times. However, high-power interference signals from ground radars tend to cause receiver saturation, leading to nonlinear distortion. This results in power loss in the fundamental component and generates homologous harmonics that compete with the fundamental, both severely degrading the fundamental jamming-to-noise ratio (JNR) and reducing the accuracy of existing fundamental time difference of arrival (TDOA)-based localization. To address this, this paper proposes a novel approach that turns the otherwise harmful harmonic components into beneficial resources to enhance localization performance. The fundamental and third-harmonic pulses are first extracted and separated from the SAR echoes. Theoretical and observed TDOA sequences are then computed for both components. Finally, accurate localization is achieved through a joint loss function. Simulations using the Geometric Dilution of Precision (GDOP) demonstrate that the proposed method improves localization accuracy under saturation compared to existing TDOA-based approaches. Experiments with GF-3B satellite dual-pass data confirm its effectiveness, reducing the localization error to 2.08 km.