Open-Loop Correlators for GNSS Multipath Alignment Error
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Solution Overview
Problem
Global navigation satellite system (GNSS) receivers face alignment errors due to multipath signals, which distort the correlation function and affect pseudo-range calculations, leading to position determination errors of several meters.
Innovation Solution
The introduction of additional correlators operating in open-loop mode allows for the estimation and correction of alignment errors between the local sequence and the PRN sequence received along the line-of-sight path, without affecting the delay-locked loop or phase-locked loop operations, by using threshold delays and signal processing to mitigate multipath effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional correlators are introduced to estimate alignment errors, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system segments the correlation function measurement into multiple independent components by introducing additional correlators that measure specific points (maximum point and at least one other point) separately. This segmentation allows independent estimation of alignment errors without requiring complete system redesign.
Solution Approach 2:
The additional correlators act as intermediary measurement devices that indirectly estimate alignment errors by measuring correlation function values at specific points. These intermediaries provide alignment error information without directly interfering with the primary delay-locked loop operation.
2Reliability
If open-loop correlators are used for alignment error estimation, then reliability is improved by not affecting DLL or PLL operations, but device complexity increases
Solution Approach 1:
The measurement system is segmented into independent open-loop correlators that operate separately from the closed-loop DLL and PLL systems. This segmentation ensures that alignment error estimation does not interfere with the stability and reliability of the primary tracking operations.
Solution Approach 2:
The open-loop correlators provide feedback information about alignment errors without forming a closed feedback loop that would affect DLL or PLL operations. This allows the system to maintain reliability by preventing feedback interference while still utilizing measurement information.
Data Source
AI summary
Described herein is a receiver for a navigation system, which receives a navigation signal modulated with a pseudorandom sequence along a line-of-sight path and reflected paths. The receiver includes a delay-locked loop, which generates a local sequence, and a first correlator and a second correlator, which operate in open-loop mode and generate a first correlation signal.