GNSS Signal Processing Device Code Phase Tracking
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Solution Overview
Problem
Existing GNSS signal tracking methods struggle with maintaining accurate lock on the code phase of direct wave signals due to interference from multipath signals, leading to degraded tracking accuracy when the code phase enters an insensible range.
Innovation Solution
A GNSS signal processing method that utilizes a correlating process with multiple replica signals and differential value calculations to determine error detection values, allowing for precise code phase control and tracking performance improvement by selecting appropriate error detection methods based on differential value signs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insensible range is set to avoid multipath signal interference, then tracking reliability improves, but the code phase may enter the insensible range during capture-to-tracking transition, causing loss of lock
Solution Approach 1:
The patent dynamically adjusts the error detection threshold based on the capture process results. During capture, a larger code phase interval is used to quickly acquire signal, and then the threshold is adjusted for tracking. This dynamic adaptation allows the system to transition from a permissive capture mode to a precise tracking mode, resolving the contradiction between maintaining lock reliability and achieving precise code phase locking.
Solution Approach 2:
The patent changes the parameter of error detection threshold from a fixed value to a variable that depends on the capture process outcome. By modifying this parameter based on the transition stage, the system can accommodate both the need for robust multipath rejection during tracking and the need for flexible code phase acquisition during capture, thereby resolving the contradiction.
2Productivity
If a large code phase interval is used for replica signals during capture, then capture speed improves, but the code phase difference remains large during transition to tracking, increasing risk of entering insensible range
Solution Approach 1:
The system dynamically adapts the code phase interval based on the operational stage. During capture, a larger interval is used to speed up acquisition. After capture, the system transitions to a smaller interval for tracking, ensuring precise code phase locking and preventing entry into the insensible range. This dynamic adjustment resolves the contradiction between capture speed and tracking stability.
Solution Approach 2:
The capture process serves as a preliminary action that prepares the system for accurate tracking. By using a larger code phase interval during capture to quickly acquire the signal, the system establishes an initial lock that can then be refined. The capture results inform the subsequent tracking parameters, ensuring a smooth transition that maintains reliability while achieving speed.
3Device complexity
If conventional error detection method is used, then device complexity remains low, but tracking accuracy degrades when code phase enters insensible range due to multipath signals
Solution Approach 1:
The patent applies different error detection methods locally based on the operational context. During capture, a simpler method is used, while during tracking, a more sophisticated method with adaptive thresholding is employed. This local differentiation allows the system to maintain low complexity during capture while achieving high accuracy during tracking, resolving the contradiction between complexity and precision.
Solution Approach 2:
The error detection method changes its parameters (threshold values, calculation equations) based on the operational stage and signal conditions. This parameter adaptation allows the system to achieve high tracking accuracy when needed while maintaining acceptable performance with lower complexity during capture, thereby resolving the contradiction between device complexity and measurement precision.
Data Source
AI summary
A demodulation unit for a GNSS signal processing device includes an operator that selects an error detecting method based on signs of early and late differential values and calculates an error detection value. A code phase range where an error detection value is not 0 is wide with a first error detecting method, and is narrow with a second. Immediately after capturing a GNSS signal, a code phase difference between the GNSS signal and a prompt replica signal is large, and signs of the early differential value and the late differential value are different from each other. In this case, the first method is used. As the code phase is driven, the code phase difference between the GNSS signal and the prompt replica signal becomes smaller, and the signs of the early differential value and the late differential value become the same. In this case, the second method is used.