GNSS Carrier Phase Estimation from Code-Free Samples Under Deep Fading
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Solution Overview
Problem
GNSS receivers face challenges in accurately tracking Global Navigation Satellite System signals under challenging reception conditions, such as multipath and deep fading, which can lead to inaccurate position calculations and loss of signal lock.
Innovation Solution
A method and apparatus for processing GNSS signals by generating code-free samples that decouple carrier phase estimation from real-time tracking, allowing for analysis of past and future signal samples to improve sensitivity and robustness to deep fading, using a tracking loop independent of estimation for positioning calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If carrier phase tracking uses real-time estimates from tracking loops, then the system operates with low latency, but the estimation accuracy deteriorates under deep fading conditions
Solution Approach 1:
The patent stores code-free samples in advance for a duration longer than the processing interval, enabling post-processing analysis that looks beyond immediate real-time constraints. This preliminary accumulation of data allows the system to perform more accurate carrier phase estimation by analyzing extended sample sequences when signal conditions permit, thereby improving measurement precision without sacrificing real-time operational capability.
2Measurement precision
If the receiver uses conventional tracking loops, then the system structure remains simple, but sensitivity to weak signals deteriorates
Solution Approach 1:
The patent divides the receiver architecture into distinct functional segments: a tracking loop that maintains simple real-time operation, and a separate post-processing engine that performs enhanced carrier phase estimation on stored code-free samples. This segmentation allows the sensitivity improvement to be achieved in the post-processing segment without complicating the core tracking loop architecture, thereby enhancing signal detection sensitivity while maintaining relative structural simplicity.
3Reliability
If carrier phase estimates are decoupled from tracking loops, then estimation robustness improves, but system complexity increases
Solution Approach 1:
The patent merges the benefits of complex post-processing with the simplicity of conventional tracking by having the post-processing engine use the tracking loop's code-free samples as input. The decoupled carrier phase estimation combines information from extended sample sequences while leveraging the tracking loop's existing signal acquisition, thereby improving robustness to deep fading without fully duplicating the tracking functionality and avoiding excessive complexity multiplication.
Data Source
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AI summary
A method and apparatus are provided for processing a GNSS signal received at a receiver. The method includes obtaining samples of the GNSS signal. The samples contain a carrier signal modulated by a spreading code. The method includes generating, based on the obtained samples, code-free samples. These code-free samples contain the carrier signal but the spreading code has been wiped off. The method may include storing a sequence of the code-free samples, the sequence having an associated duration. Additionally, the method comprises analysing the sequence of code-free samples to estimate one or more signal characteristics over the duration of the sequence. The signal characteristics include a carrier phase of the carrier signal.