GPS Receiver Peak Frequency Correction for Low Signal Synchronization
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Solution Overview
Problem
Existing GPS positioning systems face challenges in accurately determining the phase of the C/A code when the signal strength of satellite radio waves is extremely low, leading to difficulties in synchronizing codes and estimating the true phase due to deformation of the correlation value graph and equal correlation values at multiple positions.
Innovation Solution
A positioning device comprising a peak frequency determination section, reference frequency calculation section, reference correlation value calculation section, and corrected peak frequency calculation section to accurately determine the peak frequency and receive radio waves using the corrected peak frequency, even at low signal strengths, thereby ensuring precise positioning without relying on accurate IF carrier frequency estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If code synchronization is performed using traditional correlation methods, then positioning accuracy is maintained under normal signal conditions, but code synchronization becomes impossible when satellite radio wave strength is extremely low
Solution Approach 1:
The patent changes the correlation method from traditional single-point correlation to a method that calculates correlation values at multiple frequency points (peak frequency and both sides). This parameter change in the correlation approach enables reliable code synchronization even when signal strength is extremely low, as it allows identification of the true peak frequency despite graph deformation
Solution Approach 2:
The patent introduces an intermediary process of calculating correlation values at multiple frequency points (peak frequency ± offset frequencies) to mediate between the degraded correlation graph and accurate code phase determination. This intermediary calculation method enables reliable frequency identification even when the direct correlation graph is deformed by low signal strength
2Measurement precision
If PLL frequency synchronization is used, then frequency synchronization accuracy is high under strong signal conditions, but frequency synchronization cannot be achieved when satellite radio wave strength is low
Solution Approach 1:
The patent performs preliminary correlation calculations at multiple frequency points before final frequency determination. By pre-calculating correlation values at the peak frequency and both side frequencies, the system prepares sufficient data to identify the true peak frequency even when signal strength is low, enabling subsequent accurate code synchronization without relying on PLL
Solution Approach 2:
The patent implements a feedback mechanism where correlation values from multiple frequency points are used to determine the true peak frequency. The calculated correlation values provide feedback about signal characteristics at different frequencies, enabling the system to identify the correct peak frequency and achieve accurate code synchronization even under low signal conditions
3Measurement precision
If IF carrier frequency estimation is performed, then code phase estimation can be improved, but accurate positioning cannot be achieved when signal strength is extremely low due to graph deformation
Solution Approach 1:
The patent performs excessive correlation calculations by computing correlation values not only at the peak frequency but also at both side frequencies (peak frequency ± offset). This partial redundancy in calculations provides sufficient information to identify the true peak frequency even when the correlation graph is deformed, ensuring reliable code phase estimation and positioning accuracy under low signal conditions
4Productivity
If correlation process is performed at single peak frequency, then calculation speed is fast, but positioning accuracy deteriorates when signal strength transitions from high to low
Solution Approach 1:
The patent segments the frequency spectrum into multiple points (peak frequency and both side frequencies) for correlation calculation. Instead of performing a single correlation at one frequency, the system divides the frequency analysis into multiple discrete points, enabling accurate identification of the true peak frequency while maintaining efficient calculation through targeted frequency sampling
Data Source
AI summary
A positioning device comprising: a peak frequency determination section which determines a peak frequency which is a reception frequency corresponding to a maximum correlation value of a specific positioning base code replica and a positioning base code carried on a radio wave from a specific transmission source; a reference frequency calculation section which calculates a low frequency which is a frequency lower than the peak frequency and a high frequency which is a frequency higher than the peak frequency; a reference correlation value calculation section which calculates the correlation value corresponding to the low frequency and the correlation value corresponding to the high frequency; a corrected peak frequency calculation section which calculates a corrected peak frequency based on the correlation value corresponding to the peak frequency, the peak frequency, the correlation value corresponding to the low frequency, the low frequency, the correlation value corresponding to the high frequency, and the high frequency; and a radio wave reception section which receives the radio wave using the corrected peak frequency.