With the increasing demand for high-sensitivity signal tracking in complex environments, GNSS receiver technologies have continuously evolved in both architecture and algorithmic design. This paper presents a systematic review of the development of high-sensitivity tracking techniques, with a focus on the transition from closed-loop to open-loop, hybrid, and deeply integrated architectures. Key strategies—such as coherent integration time extension, discriminator and loop filter optimization, vector tracking (VT), and Direct Position Estimation (DPE) are evaluated in the context of weak signal scenarios. To address the limitations of existing methods, including strong dependence on filter models, oscillator instability, and computational complexity, this study also outlines future research directions, including (1) integrating deep learning techniques into filter structures to enhance adaptability and robustness; (2) developing multi-channel collaborative estimation schemes to mitigate oscillator noise in weak signal environments; and (3) designing low-complexity open-loop tracking approximations to align with hardware resource constraints. Thus, enhancing the necessity of navigation continuity and robustness under low-signal-to-noise-ratio (SNR) conditions.

The rise of miniaturized wearable devices has imposed more stringent requirements on the sensitivity of satellite signal reception. However, the low-cost oscillators commonly used in wearable devices exhibit considerable frequency instability, which degrades both receiver sensitivity and tracking accuracy. To address this issue, this paper establishes a tracking jitter model that jointly accounts for thermal noise and oscillator noise, and derives an explicit expression for tracking jitter as a function of the coherent integration time. Based on the U-shaped characteristic of the resulting tracking jitter curve, an optimal coherent integration time model is further derived. In addition, the time-varying behaviors of tracking jitter contributed by different oscillator noise components are investigated, thereby characterizing the dominant role of flicker frequency noise. Both simulation and experimental results show that, for most integration intervals, flicker frequency noise is the primary source of oscillator-induced tracking jitter. Compared with several conventional coherent integration time settings, the proposed optimal coherent integration time model improves tracking accuracy by 3% to 49% and enhances sensitivity by 0.5 to 1 dB. In comparison with the Kalman filter-based optimal coherent integration method, the proposed approach achieves comparable sensitivity while preserving the low-complexity advantage of the conventional PLL, and further improves steady-state tracking accuracy by approximately 2% to 4%. These results provide a theoretical basis for oscillator selection and parameter configuration in satellite signal receiving terminals.