Publication:

Comparision of Doppler tracking techniques for Starlink satellite signals

This project focuses on the study of the use of Starlink constellation signals for Position, Navigation and Timing (PNT) as an alternative to GNSS. A summary about the structure of this type of signals giving a detail explanation about the synchronization symbols from the signals is exposed. The Doppler parameter that affects these signals when they are captured by Earth receivers is analyzed. The objective is to compare different Doppler tracking techniques to determine the quality of the architectures for Doppler compensation. Two architectures are based on well-known Phased-Locked Loop (PLL), but because they track the Doppler from the signals (frequency) they are Frequency-Locked Loop (FLL) having a second and third order close loop. Both architectures can perform the tracking successfully but not filtering the noise as perfectly for low SNR (dB). Also, the third architecture is based on a standard Kalman Filter (KF), recent architectures for signal synchronization that seem to replace the well-established PLL-architectures. Nevertheless, the algorithm developed doesn’t present better results than the FLL’s architectures. To test the tracking performance of the diverse architectures, synthetic signals have been generated. Moreover, two scenarios have been tested: the first one considers AWGN (Additive White Gaussian Noise) in addition to the Doppler effect to generate the synthetic received signals, while the second one also adds PN (Phase Noise). The results show that for the simpler architecture (first order FLL), the Doppler tracking is performing better for both noise scenarios comparing to the other developed techniques.