GNSS Phase Multi-path Mitigation via Periodic Reversals
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Solution Overview
Problem
Global navigation satellite systems (GNSS) face significant errors due to multi-path signals, which are composite of direct and reflected signals, causing phase distortion and phase errors in signal processing.
Innovation Solution
A system and method that measures composite signals during periodic phase reversals, determines phase errors using filter characteristics, and corrects for these errors in navigation computations, employing a receiver with a processor and memory to analyze the time delay and phase reversal differences between direct and multi-path signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multi-path signals are present in the composite signal, then the receiver can acquire signals from satellites, but phase errors and time errors occur due to signal reflection and delay
Solution Approach 1:
The patent segments the composite signal analysis by identifying and separating the direct-path signal components from multi-path signal components using filter characteristics. By measuring the composite signal during periodic phase reversals and comparing it with the expected direct-path signal behavior, the system isolates the multi-path induced phase errors for correction
Solution Approach 2:
The patent implements a feedback mechanism where the measured composite signal during phase reversals is used to determine phase errors, which then feed back into correcting the navigation computation. This closed-loop approach continuously mitigates multi-path errors by using the observed signal characteristics to adjust and correct measurements
2Reliability
If multi-path signals are present in the composite signal, then the receiver can detect satellite signals, but time errors occur due to different path lengths
Solution Approach 1:
The patent performs preliminary measurement of the composite signal during periodic phase reversals before final navigation computation. By capturing and analyzing the signal characteristics at these specific moments, the system预先 determines phase errors that can then be corrected in the navigation solution, preventing time errors from propagating
3Ease of manufacture
If filter band limiting is applied to direct-path and multi-path signals, then signal processing is enabled, but phase error determination requires complex filter characteristic analysis
Solution Approach 1:
The patent changes the approach from directly analyzing complex filter characteristics to measuring the composite signal during periodic phase reversals. By utilizing the known phase reversal timing and measuring signal behavior at these specific moments, the system determines phase errors through parameter comparison rather than complex filter analysis, reducing computational complexity
Data Source
AI summary
A system and method for mitigating a multi-path-induced error in a global navigation satellite system (GNSS) is described. In one embodiment of the method, a composite signal is received. The composite signal includes a band-limited direct-path signal and at least one band-limited multi-path signal that are each modulated with periodic phase reversals. The composite signal is measured as a function of time during a time interval having at least one of the periodic phase reversals. A phase error φε between the composite signal and the direct-path signal due to the multi-path signal is determined using the measured composite signal as a function of time and a pre-determined filter characteristic corresponding to a filter used to band limit the direct-path signal and the multi-path signal. The phase error φε in a navigation computation is corrected.