Joint Doppler Center Estimation for Synthetic Aperture Positioning Using Starlink Signals of Opportunity

To address the degradation of global navigation satellite system (GNSS) positioning performance in challenging environments such as signal blockage and interference, this paper investigates a high-precision positioning method based on Starlink satellite signals of opportunity. A self-developed receiving platform is used to receive and analyze a Starlink downlink narrowband beacon signal at 11.45 GHz. To overcome the challenges of unknown prior signal parameters, unknown prior frequency offset under low-SNR (signal-to-noise ratio) conditions, and the difficulty of robustly estimating the reference time, a boundary-constrained integrated stationary phase method (BISPM) is proposed to achieve joint and accurate estimation of the reception time and carrier frequency. On this basis, a tomographic synthetic aperture positioning model based on virtual steering vectors is constructed. By coherently integrating short-time observations and performing back-projection imaging, the proposed method improves positioning resolution under single-satellite conditions. Experimental results using the actually received signal from STARLINK-32494 show that, with a synthetic aperture time of 3 s and only a single satellite, positioning accuracies of approximately 0.4 m in azimuth and 8 m in range can be achieved. These results verify the feasibility of using Starlink narrowband beacon signals for opportunistic positioning and provide a useful reference for rapid and high-precision positioning with low-Earth-orbit satellite signals of opportunity.