GNSS Receiver Multipath Tracking via Dual Pseudo-Range Discrimination
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Solution Overview
Problem
Existing satellite navigation systems, particularly those using BOC signals, face challenges in accurately tracking signals in multipath propagation environments due to multipath reflections, which can lead to positioning errors and biases, as current techniques are not robust enough to distinguish between main and side peaks in such conditions.
Innovation Solution
A GNSS receiver is designed with a subcarrier and code tracking loop and a code tracking loop that calculates two pseudo ranges, allowing for the selection and modification of a discriminator value based on the difference between these pseudo ranges to improve tracking accuracy and robustness against multipath effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If BOC signals are used for satellite navigation, then positioning precision is improved due to sharper autocorrelation function peak, but tracking reliability deteriorates because side peaks compete with main peak and cause PLL to lock on wrong peaks
Solution Approach 1:
The patent introduces an intermediary detection mechanism that compares correlation values at different time offsets (prompt, very-early, very-late) to identify whether the PLL is tracking the main peak or a side peak. This intermediary detection system acts as a mediator between the ambiguous correlation peaks and the final tracking decision, allowing the system to recognize and correct side peak locking without sacrificing the precision benefits of BOC signals.
2Reliability
If Bump-Jumping technique is used to detect side peak tracking, then tracking accuracy is improved by detecting correlation amplitude, but measurement precision deteriorates because the technique is particularly sensitive to multipath reflections
Solution Approach 1:
The patent extracts only the essential information needed for side peak detection by comparing correlation amplitudes at specific time offsets (prompt, very-early, very-late), while discarding the problematic direct amplitude estimation that is sensitive to multipath. By taking out only the comparative relationship between these specific correlation values, the system maintains side peak detection capability while reducing sensitivity to multipath reflections.
3Measurement precision
If Double Estimation technique is used with C-DLL and S-DLL loops, then positioning accuracy is improved by comparing pseudo ranges, but reliability deteriorates because multipath reflections affect the loops differently causing false readjustments
Solution Approach 1:
The patent implements a feedback mechanism where the comparison result between prompt, very-early, and very-late correlation values feeds back to adjust the PLL tracking position. This feedback loop continuously monitors the correlation landscape and automatically corrects tracking errors by jumping the phase when side peak locking is detected, ensuring stable and reliable tracking without the false readjustments caused by differential multipath effects in dual-loop systems.
Data Source
AI summary
A GNSS receiver comprising a circuit configured to receive a positioning signal comprising a carrier modulated by a subcarrier and a PRN code; a subcarrier and code tracking loop, comprising a first discrimination circuit, configured to calculate a first pseudo range from said received positioning signal and a first reference signal; a code tracking loop, comprising a second discrimination circuit, configured to calculate a second pseudo range from said received positioning signal and a second reference signal; and a calculation circuit configured to evaluate a difference between said first pseudo range and said second pseudo range, and to modify the output of the first discrimination circuit accordingly.The invention further addresses a method for calculating a pseudo-range in such a GNSS receiver.