GNSS Clock Drift Correction via Doppler Frequency Difference
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current GNSS systems face challenges in quickly correcting clock drift errors, especially when the receiver is turned off and then turned on, which leads to a significant delay in obtaining accurate position fixes due to the lack of temperature compensation and the need for multiple satellite signals.
Innovation Solution
The apparatus and method utilize a Doppler correction unit, tracking unit, satellite-positioning unit, computation unit, and error correction unit to calculate an estimated clock offset by storing differences in frequencies before and after the receiver is turned off, allowing for correction without temperature sensors or additional hardware, enabling quick recalibration with a single satellite.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional GNSS systems wait for multiple satellite signals and perform full position fixes to correct clock drift, then positioning accuracy is improved, but the time required for correction increases significantly
Solution Approach 1:
The system performs preliminary clock offset calculations using frequency differences from a single satellite before full positioning is needed. The computation unit calculates clock offsets based on Doppler frequency differences and stores them for quick retrieval, eliminating the need to wait for multiple satellite signals when the receiver is restarted.
Solution Approach 2:
The patent introduces frequency difference as an intermediary parameter to estimate clock offset. Instead of directly measuring clock drift requiring multiple satellites, the system uses the difference between predicted and tracked frequencies from a single satellite as a mediator to infer and correct clock offset, enabling faster correction.
2Measurement precision
If temperature sensors and temperature compensation methods are used to correct clock drift, then clock accuracy is improved, but device complexity and hardware requirements increase
Solution Approach 1:
The system uses itself to correct its own clock errors by measuring frequency differences from satellite signals. The receiver's own tracking unit provides the tracked frequency, which is compared with the predicted frequency to calculate clock offset, eliminating the need for external temperature sensors or additional compensation hardware.
Solution Approach 2:
The patent replaces the mechanical/physical approach of temperature sensing and thermal compensation with a signal-processing approach. Instead of using temperature sensors to detect clock drift and applying thermal compensation algorithms, the system substitutes this with Doppler frequency difference measurement and computational clock offset estimation.
3Reliability
If the receiver processes multiple satellite signals to achieve accurate position fixes, then positioning reliability is improved, but the search time for weak signals and processing time increase
Solution Approach 1:
The system performs preliminary clock offset estimation using a single satellite signal before full positioning processing. This preliminary action prepares the clock correction data in advance, so when multiple satellite signals are processed for positioning, the clock is already corrected, reducing overall processing time and improving productivity without sacrificing reliability.
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 approach allows for rapid correction of clock drift errors and reduces the time required for new position fixes, even without temperature compensation, ensuring accurate satellite positioning and reducing search time for weak GNSS signals.
Implementation Method 1
A first predicted frequency is obtained by performing Doppler correction to the first GNSS signal based on Doppler information derived from the first GNSS signal
Data Source
AI summary
In an apparatus of correcting a clock drift error, a receiver unit receives a first GNSS signal from a satellite. A Doppler correction unit obtains a first predicted frequency. A tracking unit can obtain a first tracked frequency. The satellite-positioning unit determines a clock offset based on a position fix. A computation unit calculates a first difference between the first predicted and tracked frequencies. When the receiver unit is turned off and then on for receiving a second GNSS signal from the satellite, the Doppler correction unit obtains a second predicted frequency, the tracking unit obtains a second tracked frequency, and the computation unit calculates a second difference between the second predicted and tracked frequencies. An error correction unit computes an estimated clock offset according to the clock offset, the first difference, and the second difference.