GNSS Tracking Loop for Multipath LOS Signal Identification
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Solution Overview
Problem
GNSS receivers face challenges in accurately tracking satellite signals due to multipath interference, which occurs when indirect signals are reflected, diffracted, or scattered en route, leading to distorted correlation functions and errors in code and carrier tracking loops, especially in mobile environments.
Innovation Solution
A tracking loop system that utilizes frequency-time-domain correlation to identify the line-of-sight (LOS) signal by correlating received satellite signals with replica codes and carrier signals, employing a Central Parameter Generator (CPG) to determine a-priori LOS parameters, and a discrete Fourier transform (DFT) to distinguish between LOS and multipath signals, enabling long coherent integration for improved signal resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multipath signals are not mitigated, then the signal strength is maintained, but the positioning accuracy deteriorates due to incorrect signal processing
Solution Approach 1:
The patent segments the received signal into direct path components and multipath components by analyzing arrival times and signal characteristics. The signal processing is divided into multiple stages: initial signal reception, multipath detection, parameter estimation, and corrected positioning calculation, allowing selective mitigation of harmful multipath components while preserving direct path signals
Solution Approach 2:
The patent introduces intermediate parameters including signal arrival time, signal strength, and path geometry characteristics as mediators to distinguish between direct and multipath signals. These intermediate measurements enable the system to identify and separate multipath components before final positioning calculation, resolving the contradiction between maintaining signal strength and eliminating interference
2Reliability
If traditional positioning algorithms are used without multipath mitigation, then the device complexity is low, but the reliability of positioning deteriorates in environments with multipath signals
Solution Approach 1:
The patent performs preliminary multipath detection and parameter estimation before final positioning calculation. By identifying multipath components in advance and estimating their characteristics (arrival time, strength, direction), the system prepares corrected signal data that can be fed into standard positioning algorithms, thereby improving reliability without requiring complete redesign of the positioning pipeline
Solution Approach 2:
The patent implements feedback mechanisms where positioning results and signal characteristics are continuously monitored to detect multipath conditions. The system adjusts signal processing parameters based on detected multipath patterns, creating a closed-loop system that adapts to varying environmental conditions and maintains reliable positioning
3Productivity
If multipath signals are processed along with direct signals, then the signal utilization is maximized, but the positioning accuracy deteriorates due to incorrect signal processing
Solution Approach 1:
The patent applies different processing qualities to different signal components. Direct path signals receive standard processing, while multipath signals undergo specialized analysis and correction. The system adjusts processing intensity and methods locally based on signal origin, maximizing useful information extraction from direct signals while applying targeted mitigation to multipath components
Data Source
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AI summary
A tracking loop and associated method for tracking a satellite signal in a GNSS receiver and for determining a line-of-sight (LOS) signal from a plurality of satellite signals received by the GNSS receiver from a satellite. One or more first correlators undertake a correlation between a code signal derived from one of the received satellite signals and a plurality of corresponding replica code signals to determine a plurality of code correlation sums comprising a prompt code correlation sum, one or more early code correlation sums and one or more late code correlation sums. One or more second correlators correlate the plurality of code correlation sums with a plurality of replica carrier signals, each having a different Doppler frequency offset, to determine, for each of the plurality of code correlation sums, a set of correlation magnitudes at frequencies of the plurality of replica carrier signals. An LOS identification module identifies the LOS signal based on a signal propagation delay corresponding to one or more local maxima within the sets of correlation magnitudes.