GNSS Signal Processing Using Geometry and Ionosphere Filters
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Solution Overview
Problem
Existing GNSS systems face challenges in accurately processing signals from satellites with mixed numbers of carrier frequencies, particularly during transitional periods when some satellites broadcast three frequencies while others only broadcast two, leading to difficulties in ambiguity estimation.
Innovation Solution
The implementation of a method that combines geometry filters, ionosphere filters, and auxiliary ionosphere filters to process GNSS signal data from satellites with two and three or more carriers, using combinations such as two-frequency geometry carrier-phase, single-frequency carrier-phase and code, and auxiliary ionospheric combinations to generate combined ambiguity estimates, thereby improving ambiguity estimation and position determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a unified processing method is used for all satellites, then device complexity is reduced, but measurement precision deteriorates due to inability to handle mixed-frequency signals accurately
Solution Approach 1:
The patent segments the GNSS satellite constellation into three distinct groups based on carrier frequency availability: two-frequency satellites (L1, L2), three-frequency satellites (L1, L2, L5), and single-frequency satellites (L1 only). Each segment is processed using specialized filter combinations tailored to its frequency characteristics, allowing accurate ambiguity estimation for each group while maintaining overall system manageability through this structured segmentation approach.
2Measurement precision
If separate processing methods are used for different satellite types, then measurement precision is improved, but device complexity increases due to multiple filter combinations
Solution Approach 1:
The patent implements a universal multi-frequency processing framework where a single receiver architecture can handle two-frequency, three-frequency, and single-frequency satellites simultaneously. The system uses a unified state-space model that accommodates different frequency combinations through configurable filter banks, allowing one system to perform multiple processing functions without requiring separate dedicated processors for each satellite type.
Solution Approach 2:
The patent applies local quality by assigning specific filter combinations to specific satellite frequency groups: geometry-free filters for two-frequency satellites, ionosphere-free filters for three-frequency satellites, and single-frequency pseudorange filters for L1-only satellites. Each local processing module is optimized for its specific frequency input, improving accuracy while the overall system maintains coordination through a unified estimation framework.
3Measurement precision
If all three-frequency combinations are used, then measurement precision is improved, but adaptability deteriorates due to inability to process satellites with fewer frequencies
Solution Approach 1:
The patent implements dynamic adaptability where the receiver automatically adjusts its processing mode based on the available frequency combinations from each satellite. The system dynamically selects appropriate filter combinations: using three-frequency ionosphere-free processing when L1, L2, and L5 are available, switching to two-frequency geometry-free processing when only L1 and L2 are present, and falling back to single-frequency pseudorange processing when only L1 is available. This dynamic adaptation ensures continuous operation across varying signal conditions.
Data Source
AI summary
Methods and apparatus are provided for processing a set of GNSS signal data derived from signals of a first set of satellites having at least three carriers and signals of a second set of satellites having two carriers. A geometry filter uses a geometry filter combination to obtain an array of geometry-filter ambiguity estimates for the geometry filter combination and associated statistical information. Ionosphere filters use a two-frequency ionospheric combination to obtain an array of ionosphere-filter ambiguity estimates for the two-frequency ionospheric combinations and associated statistical information. Each two-frequency ionospheric combination comprises a geometry-free two-frequency ionospheric residual carrier-phase combination of observations of a first frequency and observations of a second frequency. Auxiliary ionosphere filters use an auxiliary ionospheric combination to obtain an array of auxiliary-ionosphere-filter ambiguity estimates for the auxiliary ionospheric combinations and associated statistical information. Each auxiliary ionospheric combination uses carrier-phase observations of a third frequency and carrier-phase observations of at least one of the first frequency and the second frequency. A combined array of ambiguity estimates is prepared for all carrier phase observations and associated statistical information by combining the arrays of the geometry filter and the ionosphere filters and the auxiliary ionosphere filters.