Adaptive Code Phase Tracking for GNSS Multipath Rejection
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Solution Overview
Problem
Existing GNSS signal processing methods struggle to maintain accurate tracking of direct wave signals when multipath signals are present, leading to increased pseudorange and positioning errors, especially when the code phase of the direct wave signal enters an insensible range or when reception sensitivity is low.
Innovation Solution
A GNSS signal processing method that correlates the received signal with multiple replica signals to calculate differential values, allowing for adaptive code phase control based on error detection values, which includes setting thresholds for differential values to select between wide and narrow code phase ranges to prevent signal loss and maintain accurate tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an insensible range is set to avoid multipath signal influence, then multipath signal rejection is improved, but tracking of direct wave signal may be lost when code phase enters the insensible range
Solution Approach 1:
The patent dynamically adjusts the code phase search range based on signal conditions. When multipath signals are detected, the insensible range is temporarily expanded to reject them, while when direct wave signals are weak, the search range is expanded beyond the normal insensible range to prevent loss of tracking. This dynamic adjustment resolves the contradiction between multipath rejection and tracking continuity.
Solution Approach 2:
The patent changes the code phase range parameter adaptively. The code phase search range is adjusted based on the correlation values and signal conditions. When the direct wave signal is weak or multipath interference is detected, the range is expanded to ensure the direct wave code phase remains within the searchable range, preventing tracking loss while maintaining multipath rejection capability.
2Device complexity
If a fixed code phase range is used for tracking, then processing simplicity is improved, but tracking accuracy degrades when reception conditions change
Solution Approach 1:
The patent implements dynamic code phase range adjustment based on reception conditions. The code phase search range is not fixed but is adapted according to signal strength, multipath conditions, and tracking state. This dynamic approach maintains processing simplicity while improving tracking accuracy under varying reception conditions.
Solution Approach 2:
The patent uses feedback from correlation values and tracking error to adjust the code phase search range. The system continuously monitors the reception state and adjusts the code phase range accordingly, ensuring optimal tracking accuracy without excessive processing complexity. The feedback mechanism allows the system to adapt to changing conditions automatically.
3Object-affected harmful factors
If the code phase of prompt replica signal deviates from the aimed GNSS signal, then multipath signal tracking may occur, but intentional deviation causes loss of direct wave signal tracking
Solution Approach 1:
The patent extracts and identifies the direct wave signal component from the combined signal using correlation analysis. By calculating correlation values at different code phases and identifying peaks, the system separates the direct wave signal from multipath signals. This extraction allows the system to track the direct wave signal even when multipath signals are present and to distinguish between intentional deviation and actual signal phase.
Solution Approach 2:
The patent uses feedback from correlation value analysis to detect when the prompt replica signal code phase has deviated from the direct wave signal. By monitoring the correlation values and their changes, the system can identify when multipath tracking is occurring and adjust the code phase to return to the direct wave signal, preventing loss of direct wave tracking while maintaining multipath rejection.
Data Source
AI summary
A demodulation unit for a GNSS signal processing device includes an operator that uses a first error detecting method when one of a first selection criterion in which an early late differential value is higher than a first threshold (positive value) and an early differential value is lower than a third threshold (negative value), and a second selection criterion in which the early late differential value is lower than a second threshold (negative value) and a late differential value is lower than a fourth threshold (negative value) is satisfied, and the operator uses a second error detecting method when neither criterion is satisfied. A code phase range where an error detection value is not 0 is wide with the first error detecting method, and the code phase range where the error detection value is not 0 is narrow with the second error detecting method.