Passive GNSS-based SAR imaging with sub-apertures combination

The passive global navigation satellite system (GNSS)-based synthetic aperture radar (SAR), known as GNSS-SAR, is a newly developing radar sensing tool in recent decade. However, if the system is characterized by a nonlinear trajectory under wide viewing angles, the azimuth resolution will be negatively affected. To address the issue, this paper proposes a new GNSS-SAR imaging method based on sub-apertures combination. In the proposed method, the full-length aperture is partitioned into several sub-apertures according to the trajectory length, the expected azimuth resolution, and the dwell time on each point scatter. Then within each sub-aperture, to enhance signal-to-noise ratio, imaging is performed based on the algorithm in the first author’s work (Zheng et al. in SIViP 13(8):1549–1557, 2019). Finally, the imaging results in the sub-apertures are consecutively combined to obtain the full GNSS-SAR image. The proposed method was examined via simulation and a field experiment using BeiDou B3I as the signal of opportunity. The results revealed that the proposed method can provide a higher azimuth resolution for non-straight trajectory under multi-scene conditions.