Dual-Polarized GNSS Receiver Multipath Mitigation
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Solution Overview
Problem
GNSS receivers face challenges in accurately distinguishing between direct and reflected signal paths in multipath propagation environments, leading to pseudo range measurement errors and reduced positioning accuracy, especially in urban areas where multipath reflections are prevalent.
Innovation Solution
A dual-polarized GNSS receiver architecture utilizing both right-hand circularly polarized (RHCP) and left-hand circularly polarized (LHCP) antennas, with associated RF chains, to calculate pseudo range measurements and quality indicators, allowing for the selection and exclusion of pseudo ranges likely to come from reflected paths, thereby improving multipath detection and reducing false alarms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RHCP antennas are used to mitigate multipath reflections, then the power level of reflected signals is greatly decreased, but the efficiency highly depends on the quality of the receiving antenna diagram and some propagation environments still remain an issue
Solution Approach 1:
The patent segments the signal reception process by using separate RHCP and LHCP antennas with independent RF chains, allowing parallel processing of both polarizations. This segmentation enables the system to independently analyze and compare signals from different polarizations, improving multipath detection capability without requiring a single complex antenna diagram
Solution Approach 2:
The patent adds the polarization dimension to signal processing by simultaneously receiving and processing both RHCP and LHCP signals. This dimensional expansion allows the system to distinguish direct and reflected paths based on polarization characteristics, providing an additional degree of freedom for multipath mitigation beyond traditional single-antenna approaches
2Measurement precision
If tracking loops lock on reflected paths instead of direct paths, then pseudo range measurement errors occur and positioning accuracy is reduced, but detecting and distinguishing between direct and reflected paths in multipath environments is challenging
Solution Approach 1:
The patent implements feedback mechanisms where pseudo-range measurements and quality indicators from both RHCP and LHCP antennas are continuously compared and analyzed. The system uses this feedback to identify tracking loops that have locked onto reflected paths and adjusts tracking accordingly, improving measurement precision through iterative correction
Solution Approach 2:
The patent changes the polarization parameter of received signals by processing both RHCP and LHCP components separately. This parameter change enables the system to exploit polarization differences between direct and reflected signals, making path discrimination easier and improving pseudo-range measurement accuracy
3Measurement precision
If dual-polarized antenna architecture is implemented to improve multipath detection, then positioning accuracy in multipath environments is improved, but implementation complexity increases
Solution Approach 1:
The patent segments the receiver architecture into independent RHCP and LHCP processing chains, allowing modular implementation and processing. This segmentation enables parallel signal processing without requiring complex interdependencies between polarization channels, managing architectural complexity through structured modularity
Solution Approach 2:
The patent designs the dual-polarized receiver with universal processing components that handle both RHCP and LHCP signals through common RF chains and baseband processing. This multi-functionality approach reduces overall complexity by sharing resources between polarization channels while maintaining the ability to independently process each polarization
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances the accuracy of position calculations by effectively differentiating between direct and reflected signal paths, reducing the risk of false alarms and improving positioning accuracy in multipath environments with low implementation complexity and real-time processing capabilities.
Implementation Method 1
the first signal acquisition element is a right hand circularly polarized antenna... the second signal acquisition element is a left hand circularly polarized antenna
Implementation Method 2
the received signals are correlated in tracking loops with locally generated replica of the PRN code, in order to determine the origin of the signals and acquire a tracking position
Implementation Method 3
the polarization of a circularly polarized electromagnetic wave is inverted when the wave is reflected. Thus, to bring robustness against multipaths to the receivers, right hand circularly polarized (RHCP) signals are commonly used. After being reflected, the signal is left hand circularly polarized (LHCP)
Data Source
Figure 1~2
Figure 3
Figure 4a
AI summary
The invention refers to a GNSS receiver, and associated method, for calculating a position from positioning signals transmitted by a plurality of GNSS transmitters, said receiver comprising a first and a second signal acquisition elements (301) having different polarizations, the receiver being configured to process the signals received on said first signal acquisition element to calculate first pseudo range measurements (203), and the signals received on said second signal acquisition element to calculate second pseudo range measurements (303) and associated quality indicators (304), said receiver comprising a calculation circuit (306) configured to : - select at least one of the second pseudo range measurements depending on the quality indicators, and compare it with the corresponding first pseudo range measurement, and - select at least three first pseudo range measurements based on the comparison results to calculate a position (204).