Performance Comparison of Difference Correlator and Co-op Tracking Architectures Under Receiver Clock Instability

Oscillator phase noise can significantly degrade weak signal tracking performance. This paper analyzes and compares two tracking loop architectures to address the oscillator phase noise problem. The first architecture, known as the co-op tracking loop, attempts to estimate the instantaneous clock phase and exclude it from the incoming signals before tracking the LOS dynamics. The second method, known as the difference correlator, eliminates the phase noise by subtracting two channel instantaneous phases at the correlator level. The contributions of this paper include comprehensive analyses supported by simulations to evaluate the combined effect of Additive White Gaussian Noise (AWGN) and oscillator clock phase noise on the tracking performance of these two architectures. In addition, the impact of dissimilar transit times for different satellites on tracking performance is investigated.