GNSS Snapshot Receiver Secondary Code Index Adjustment
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Solution Overview
Problem
Traditional GNSS positioning systems face challenges in achieving centimeter-level accuracy with carrier-phase measurements, especially when receiving extremely short snapshot signals, due to uncertainties in encoded data bits leading to phase errors and ambiguity in secondary code hypotheses.
Innovation Solution
A method for carrier phase ready coherent acquisition of GNSS snapshot signals involves multi-hypothesis acquisition, adjustment of secondary code index hypotheses based on flight time differences, and filtering to select a common index, allowing for accurate acquisition without half-cycle errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional carrier-phase measurements are used with short snapshot signals, then positioning accuracy can be improved, but phase errors occur due to uncertainties in encoded data bits
Solution Approach 1:
The system performs preliminary alignment of secondary code phases from multiple satellites to a common time reference before making the final measurement decision. This preliminary action resolves the ambiguity of which secondary code hypothesis is correct by establishing temporal consistency across satellites, allowing reliable carrier-phase measurements even with short snapshot signals
2Measurement precision
If multiple secondary code hypotheses are evaluated to resolve phase ambiguity, then measurement precision improves, but device complexity increases
Solution Approach 1:
The system uses feedback from the temporal alignment of secondary code phases across multiple satellites to identify and select the correct secondary code hypothesis. By checking which hypothesis produces consistent alignment times across satellites, the system resolves phase ambiguity without requiring exhaustive evaluation of all possible hypotheses, thus reducing computational complexity
Data Source
AI summary
The carrier phase ready coherent acquisition of a global navigation satellite system (GNSS) snapshot signal includes receiving in a snapshot receiver different GNSS signals from correspondingly different GNSS satellites, and performing multi-hypothesis (MH) acquisition upon each of GNSS signal in order to produce a complete set of secondary code index hypotheses, each hypothesis producing a corresponding acquisition result according to an identified peak at a correct code-phase and Doppler frequency. The secondary code index hypotheses are adjusted for each different GNSS signal based upon a flight time difference determined for each GNSS satellite, so as to produce a new set of hypotheses. Finally, one of the hypotheses in the new set may be selected as a correct hypothesis according to a predominate common index amongst the hypotheses in the new set, and the acquisition results for each of the different GNSS signals may be filtered utilizing the correct hypothesis.