Phase Discriminator Using Doppler Error Compensation
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Solution Overview
Problem
Satellite radio navigation systems face challenges in accurately estimating phase errors due to rapid Doppler frequency variations and low signal-to-noise ratios, limiting their positioning accuracy and resistance to phase dynamics, especially in applications like airborne navigation where phase velocity variations are significant.
Innovation Solution
A phase discriminator device that uses a frequency-extended winding discriminator to estimate phase errors by calculating the phase estimate at each sample using specific mathematical relations, incorporating a frequency discriminator to measure Doppler frequency errors and correct phase errors, thereby expanding the capture zone of the phase loop without increasing the signal-to-noise ratio or calculation load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the passband of the loop is increased to improve resistance to Doppler frequency variations, then the resistance to phase dynamics is improved, but the calculation load increases
Solution Approach 1:
The phase error measurement is segmented into two components: a coarse frequency discriminator output that captures large phase variations, and a fine phase discriminator output that provides precise phase measurement. This segmentation allows the system to handle large Doppler shifts without requiring a wide passband, thereby reducing calculation load while maintaining resistance to phase dynamics
Solution Approach 2:
A frequency discriminator is introduced as an intermediary component that processes the signal before the phase discriminator. This intermediary extracts frequency error information and uses it to pre-compensate or guide the phase discrimination process, enabling the phase-locked loop to track rapid phase variations without increasing the overall loop bandwidth or calculation complexity
2Adaptability or versatility
If a winder discriminator is used to expand the capture zone in phase error, then the capture area becomes infinite, but the limitation in frequency error or phase speed error remains
Solution Approach 1:
The invention merges the advantages of the winder discriminator (infinite capture zone in phase error) with those of a frequency discriminator (tolerance to high phase speed errors). The frequency discriminator component specifically addresses the phase speed error limitation by providing explicit frequency error measurement and compensation, while the phase-winding discriminator maintains the expanded capture zone
3Reliability
If the sampling frequency of the phase loop is increased to handle strong phase velocity variations, then the resistance to phase dynamics is improved, but the calculation load increases
Solution Approach 1:
The system dynamically adapts its processing by using the frequency discriminator to predict and compensate for rapid phase changes. This dynamic compensation allows the phase loop to maintain accuracy under high phase velocity variations without requiring a uniformly high sampling frequency across all operating conditions, thereby reducing overall calculation load
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 significantly enhances the resistance to phase dynamics and maintains accurate positioning without increasing the signal-to-noise ratio or calculation load, effectively handling high phase velocity variations and improving the robustness of the phase-locked loop.
Implementation Method 1
The invention applies in particular to satellite radio navigation systems for which the information contained in the phase of the signal contributes to precisely determining the position of a receiver. The invention relates to a device for discriminating or estimating the phase or phase error during the demodulation of a signal subjected to significant phase variations, for example due to a rapid evolution of the frequency due to the Doppler effect.
Data Source
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AI summary
The device has a calculating unit determining phase estimation at an instant by using relations, where the relations have time interval between samples and frequency error estimation of a complex signal produced by a frequency discriminator (921). The frequency discriminator comprises a calculating unit for calculating error hypothesis of frequency. Another calculating unit of the frequency discriminator calculates the frequency error estimation. An independent claim is also included for a radio navigation signal receiving device comprising a phase discrimination device.