An Adaptive INS-Aided PLL Tracking Method for GNSS Receivers in Harsh Environments

Area of Science:

• Navigation Systems Engineering
• Signal Processing
• Control Systems

Background:

• Phase-locked loops (PLLs) are critical for Global Navigation Satellite System (GNSS) signal processing but are vulnerable to cycle slips and loss of lock in dynamic environments.
• Inertial Navigation System (INS) aid improves PLL tracking, but fixed parameters limit adaptability in harsh conditions with high dynamics and signal attenuation.

Purpose of the Study:

• To propose an adaptive INS-aided PLL that dynamically adjusts noise bandwidth and coherent integration time for improved tracking performance.
• To establish theoretical relationships between PLL tracking error and key parameters like carrier-to-noise density ratio (C/N₀), vehicle dynamics, and loop parameters.
• To optimize loop parameters for minimum tracking error in specific applications.

Main Methods:

• Developed an adaptive INS-aided PLL with adjustable noise bandwidth and coherent integration time.
• Conducted theoretical analysis to derive formulae relating PLL phase tracking error to C/N₀, vehicle dynamics, aiding update time, noise bandwidth, and integration time.
• Validated the adaptive method through software and hardware simulations.

Main Results:

• The adaptive tracking method significantly improves PLL tracking ability and integrated GNSS/INS navigation performance.
• In harsh environments, tracking sensitivity increased by 3-5 dB.
• Velocity errors decreased by 36%-50%, and position errors decreased by 6%-24% compared to traditional INS-aided PLLs.

Conclusions:

• The proposed adaptive INS-aided PLL effectively enhances GNSS/INS navigation in challenging environments.
• Dynamic adjustment of noise bandwidth and coherent integration time is crucial for optimal tracking performance.
• The adaptive approach offers substantial improvements in navigation accuracy and tracking robustness over conventional methods.