Satellite Delay Gradient Monitoring Using Parity-Corrected Phase Differences
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Solution Overview
Problem
Current ground station systems face challenges in accurately monitoring horizontal delay gradients in satellite signals due to inconsistent carrier phase measurements from reference receiver pairs, leading to missed detections or incorrect re-admittance, especially when measurements are near ±λ/2, which can result in noise cancellation and incorrect data re-admittance.
Innovation Solution
A processing function that includes a satellite differencing module, a double differencing module, a parity test module, and a gradient estimator module, which receives carrier phase measurements from multiple reference receivers, forms and compensates double-differences, performs modulo operations, and applies a parity test to correct for inconsistencies and estimate horizontal delay gradients, ensuring accurate detection of excessive delay gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carrier phase measurements from reference receiver pairs are used for gradient monitoring, then the monitoring function can operate, but inconsistent measurements near ±λ/2 lead to missed detections or incorrect re-admittance
Solution Approach 1:
The system performs preliminary actions by computing multiple alternative gradient estimates using different reference receiver pair combinations before final detection. By pre-calculating multiple possible measurements and comparing them against expected ranges, the system identifies and corrects inconsistent measurements before they lead to missed detections or false alarms.
Solution Approach 2:
The system implements feedback by comparing the measured gradient against expected ranges and using this comparison to adjust the admission decision. When a measurement falls outside the expected range, the system uses the feedback to reject that measurement and rely on alternative estimates, thereby correcting for the inconsistency in carrier phase measurements near ±λ/2.
2Reliability
If multiple reference receiver pairs are used to improve measurement redundancy, then detection coverage is enhanced, but noise cancellation occurs when measurements are near ±λ/2
Solution Approach 1:
The system applies partial action by selectively using only those reference receiver pair measurements that fall within the expected gradient range. Instead of combining all available measurements (excessive action), the system filters out measurements near ±λ/2 that would cause noise cancellation, using only the subset of measurements that are reliable for gradient estimation.
Solution Approach 2:
The system changes the parameter of measurement selection by imposing constraints on which measurements are admissible. By requiring measurements to fall within a specific range (parameter constraint), the system avoids the harmful effect of noise cancellation while maintaining the benefits of multiple redundant measurements for enhanced detection coverage.
3Productivity
If carrier phase measurements near ±λ/2 are processed, then more data is available for gradient estimation, but incorrect re-admittance of satellite data may occur
Solution Approach 1:
The system performs preliminary validation by checking whether each carrier phase measurement falls within the expected gradient range before admitting it for satellite data re-admittance decisions. This preliminary action prevents incorrect re-admittance by filtering out measurements near ±λ/2 that would lead to erroneous conclusions, while still utilizing the maximum number of valid measurements for productivity.
Data Source
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AI summary
A processing function to monitor a horizontal delay gradient in satellite signals is provided. The processing function includes a satellite differencing module, a double differencing module, a parity test module, and a gradient estimator module. The satellite differencing module receives carrier phase measurements for at least two satellites from at least three reference receivers. The satellite differencing module determines differences in the carrier phase measurements between signals from the monitored satellite and at least one of the at least one other satellite. The double differencing module: forms double-differences between pairs of the reference receivers; compensates the double-differences between the pairs; performs a modulo operation; and averages the double differences. The parity test module inputs the averaged compensated double differences when the average exceeds a parity enable threshold. The gradient estimator module configured is to estimate a magnitude of the horizontal delay gradient.