GPS Satellite Tracking Function Implementation

This document presents a method for implementing GPS satellite tracking functionality. Specifically, we employ a dual-loop approach where the carrier tracking loop integrates a phase-locked loop (PLL) with frequency-locked loop (FLL) assistance, while the code tracking loop implements a delay-locked loop (DLL) structure. The carrier tracking implementation utilizes FLL for rapid initial frequency acquisition and coarse tracking, followed by PLL for precise phase alignment and steady-state tracking. This hybrid approach typically involves cross-product frequency discriminators and phase discriminators operating on in-phase (I) and quadrature (Q) components from baseband processing. For code tracking, the DLL architecture employs early, prompt, and late correlators to maintain code phase alignment through non-coherent discrimination algorithms. The implementation commonly features adjustable loop bandwidths and integration periods optimized for different signal conditions. These techniques significantly enhance GPS satellite tracking accuracy and stability by maintaining robust synchronization under dynamic conditions and low signal-to-noise ratio environments. We believe this methodology contributes valuable insights for advancing GPS technology development, particularly in software-defined receiver implementations where these algorithms can be efficiently realized through digital signal processing techniques.