An Enhanced Non-Coherent Pre-Filter Design for Tracking Error Estimation in GNSS Receivers

Area of Science:

• Navigation Systems
• Signal Processing
• Estimation Theory

Background:

• Accurate tracking error estimation is crucial for Global Navigation Satellite System (GNSS) receivers, impacting position, velocity, and timing precision.
• Traditional discriminators and Kalman filter-based pre-filters are used, with pre-filters categorized as coherent or non-coherent.
• This research specifically investigates performance enhancements for non-coherent pre-filters.

Purpose of the Study:

• To analyze signal characteristics of coherent and non-coherent integration for tracking error estimation.
• To derive the probability distribution of estimation noise for the four-quadrant arctangent (ATAN2) discriminator.
• To improve the performance and effective working range of non-coherent pre-filters for GNSS tracking error estimation.

Main Methods:

• Detailed analysis of signal characteristics for coherent and non-coherent integration.
• Derivation of the probability distribution of estimation noise for the ATAN2 discriminator based on coherent integration models.
• Monte Carlo simulations to study the statistical properties of observation noise in non-coherent pre-filters.
• Integration of a fault detection and exclusion (FDE) structure into the non-coherent pre-filter design.

Main Results:

• The enhanced non-coherent pre-filter demonstrates superior estimation accuracy compared to traditional discriminators.
• In highly dynamic scenarios, accuracy improvements of 41.6% (carrier phase), 46.4% (carrier frequency), and 50.36% (code phase) were achieved over coherent pre-filters.
• The enhanced non-coherent pre-filter shows advantages over coherent pre-filters in specific carrier-to-noise density ratio ranges for code phase, carrier frequency, and carrier phase error estimation.

Conclusions:

• The enhanced non-coherent pre-filter offers significant improvements in tracking error estimation accuracy for GNSS receivers.
• The integration of FDE extends the effective working range for carrier phase error estimation.
• The proposed pre-filter is particularly effective in dynamic environments and under varying signal conditions.