GNSS Ionospheric Phase Scintillation Measurement Without Stable References
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Solution Overview
Problem
Existing navigation receivers face challenges in accurately measuring phase ionosphere scintillations, which cause anomalies in satellite signal measurements, affecting positioning precision, and current methods require expensive high-stable frequency references or fail to effectively estimate the Sigma-Phi index.
Innovation Solution
A method for measuring phase ionosphere scintillations using a GNSS receiver that calculates phase predictions, individual and common loop discriminator signals, and test statistics to estimate the Sigma-Phi index without requiring high-stable frequency references, employing a novel approach to reject noisy satellite signals and improve measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-stable frequency reference (OCXO or rubidium reference standard) is used to overcome receiver oscillator phase noise, then measurement precision of Sigma-Phi index is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts and removes the requirement for high-stable frequency references from the measurement system. By formulating a method that calculates Sigma-Phi index using only standard GNSS receiver components, it eliminates the need for OCXO or rubidium references, thereby reducing device complexity and cost while maintaining measurement capability
Solution Approach 2:
The patent replaces expensive, high-stability frequency references with inexpensive, standard TCXO components found in conventional GNSS receivers. This substitution uses readily available, low-cost components to achieve the measurement function without requiring specialized expensive equipment
2Loss of information
If phase scintillation measurements are performed using conventional methods, then ionosphere scintillation data is obtained, but positioning precision deteriorates due to signal anomalies
Solution Approach 1:
The patent segments the measurement process into distinct phases: individual loop tracking for each satellite, common loop processing for atmospheric effects, and separate Sigma-Phi index calculation. This segmentation allows independent optimization of each component and enables rejection of contaminated measurements while preserving clean ones
Solution Approach 2:
The patent implements feedback mechanisms where the common loop uses measurements from all satellites to estimate atmospheric effects, which are then fed back to correct individual satellite measurements. This feedback loop enables continuous refinement and identification of anomalous measurements that deviate from the expected atmospheric pattern
3Device complexity
If receiver oscillator with TCXO is used to reduce cost, then device complexity is reduced, but measurement precision of phase scintillations deteriorates due to hidden phase noise
Solution Approach 1:
The patent introduces an intermediary approach by using the common loop as a mediator that processes measurements from all satellites to estimate common atmospheric effects. This intermediary processing layer separates the receiver oscillator noise from the ionospheric scintillation signals, allowing accurate measurement despite using simple TCXO-based oscillators
Data Source
AI summary
Method of measuring ionosphere scintillation phase index Sigma-Phi, the method including, for each of N satellites being tracked, calculating a phase prediction at an i-th sample; for each of the N satellites, calculating an individual loop discriminator signal based on the phase prediction; rejecting the i-th samples of some of the N satellites, where K non-rejected satellites remain; calculating common loop discriminator signal based on the individual loop discriminator signals of non-rejected K satellites; calculating a phase estimate and a Doppler frequency estimate at the i-th sample for each of the N satellites based on individual loop discriminator signal; calculating test statistic based on the phase estimate at the i-th sample and an observed phase for each of the N satellites; calculating index Sigma-Phi as standard deviation estimation of the test statistic for each of the N satellites; and outputting the index Sigma-Phi for each of the N satellites.