A Two-Stage Kalman Filter-Based Carrier Tracking Loop for Weak GNSS Signals.

Area of Science:

• Signal Processing
• Navigation Systems
• Aerospace Engineering

Background:

• Kalman filter (KF)-based tracking loops offer superior sensitivity and robustness for Global Navigation Satellite System (GNSS) receivers over conventional methods.
• Improving tracking sensitivity requires longer coherent integration times, which are limited by navigation data bit sign transitions.
• Standard KF receivers initialized with acquired data struggle to converge rapidly under weak signal conditions due to frequency errors.

Purpose of the Study:

• To propose a novel two-stage KF-based tracking architecture for GNSS receivers.
• To enhance tracking sensitivity for weaker signals and accelerate convergence.
• To overcome limitations of coherent integration time and initial frequency errors in KF tracking.

Main Methods:

• A two-stage architecture comprising coarse tracking and fine tracking stages.
• The first stage refines acquired data and achieves bit synchronization.
• The second stage uses coarse tracking results for KF initialization, extending coherent integration without bit sign transition limitations.

Main Results:

• The proposed two-stage KF architecture successfully tracks weaker GNSS signals.
• It demonstrates improved tracking sensitivity compared to conventional techniques.
• The method shows significantly faster convergence than standard KF-based tracking.

Conclusions:

• The two-stage KF architecture effectively enhances GNSS receiver tracking sensitivity and reduces convergence time.
• This approach overcomes key limitations of standard KF tracking, particularly under weak signal conditions.
• The proposed method offers a more robust and efficient solution for GNSS signal tracking.