Frequency-Extended Phase Discriminator for Doppler Error Tracking
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Solution Overview
Problem
Existing satellite radionavigation systems face limitations in accurately estimating phase errors due to rapid Doppler frequency variations and low signal-to-noise ratios, leading to reduced resilience and increased computational load.
Innovation Solution
A frequency-extended winder discriminator is used to estimate phase errors by incorporating a frequency discriminator that calculates the Doppler frequency error, allowing for increased resilience to phase dynamics without increasing the signal-to-noise ratio or computational load, through equations such as θn+1=θn+Δθn+1+Δθ′n+1, where Δθ′n+1=DiscriFrequency(n+1)·2π·T1 and Δθn+1=arctan(I′n+1,Q′n+1), with I′n+1+jQ′n+1=Zn+1·Z′*n+1, and T1 being the time interval between signal samples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the passband of the phase-locked loop is increased to improve resilience to Doppler frequency variations, then the resilience to dynamics is improved, but the computational load increases
Solution Approach 1:
The phase error estimation is segmented into two independent components: a frequency-based component (Δθ′n+1) and a phase-based component (Δθn+1). This segmentation allows each component to be optimized separately, with the frequency component handling rapid variations and the phase component providing precise measurement, thereby improving resilience without proportionally increasing computational load.
Solution Approach 2:
The frequency error is estimated in advance using a frequency discriminator before the phase error calculation. This preliminary action of predicting the frequency trend allows the phase-locked loop to compensate for rapid Doppler variations proactively, improving resilience while distributing computational effort across time rather than concentrating it in the main loop.
2Adaptability or versatility
If a winder discriminator is used to extend the capture zone, then the phase error tolerance is improved, but the frequency error limitation remains
Solution Approach 1:
The invention merges the winder discriminator (which excels at handling large phase errors) with a frequency discriminator (which excels at handling frequency variations). This combination creates a hybrid discriminator that inherits the strengths of both: infinite phase capture zone from the winder and extended frequency tolerance from the frequency discriminator, resolving the limitation of using either alone.
Solution Approach 2:
The frequency discriminator acts as an intermediary that preprocesses the signal by estimating and compensating for frequency errors before the phase discriminator processes the phase information. This intermediary step enables the phase discriminator to focus on phase measurements without being overwhelmed by frequency variations, extending the overall frequency error tolerance.
3Measurement precision
If the phase-locked loop slackness is reduced to improve accuracy, then the positioning accuracy is improved, but the loop becomes more sensitive to noise
Solution Approach 1:
The measurement process is segmented into frequency estimation and phase estimation, allowing the system to optimize for accuracy in phase measurement while using frequency prediction to compensate for rapid variations. This segmentation enables reduced loop slackness without proportionally increasing noise sensitivity, as the frequency component provides a predictive framework that stabilizes the phase measurements.
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
This solution enhances the system's resilience to phase dynamics while maintaining the signal-to-noise ratio and reducing computational load, allowing for more accurate phase error estimation and improved positioning accuracy.
Implementation Method 1
a frequency discriminator that delivers as output an estimate of the frequency error and in which the said frequency discriminator comprises at least first means for computing at least two frequency error hypotheses at frequencies −F0 and +F0 with F0=Fe/2
Data Source
AI summary
In a phase discriminator device for receiving, as input, a complex signal whose argument represents a phase error, and for producing, as output, an estimate of the phase error for each signal sample Zn+1 received, the device includes a frequency discriminator and a computation part for determining the phase estimate obtained at an instant (N+1)T1. The computation part determines the phase estimate according to predetermined relations, and T1 is the time interval between two samples Zn and Zn+1, received consecutively.