Antenna Phase-Difference Estimation for TCAS Bearing Accuracy
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Solution Overview
Problem
The existing aircraft antenna systems face challenges in accurately determining the bearing of a signal source due to unreliable phase difference measurements, particularly when signal quality is poor, affecting the accuracy of traffic collision-avoidance systems.
Innovation Solution
A processor estimates the missing phase-difference value for one two-element antenna based on the expected maximum antenna element phase-difference value, predicted bearing, and elevation information, and calculates the bearing using the received phase-difference value from the other antenna, ensuring accurate bearing determination even with incomplete data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase difference measurement is used for bearing determination, then bearing accuracy can be achieved, but bearing availability deteriorates when signal quality is poor
Solution Approach 1:
The system uses feedback from the tracking filter that predicts bearing values based on previous measurements. When phase difference data is missing from one antenna, the system feeds back the predicted bearing and elevation information to estimate the missing phase difference value, thereby maintaining bearing availability while preserving accuracy.
Solution Approach 2:
The patent introduces an intermediary estimation process that uses the tracking filter's predicted bearing and elevation information to interpolate missing phase difference values. This intermediary mechanism bridges the gap between incomplete measurements and complete bearing determination, resolving the contradiction between accuracy and availability.
2Measurement precision
If phase difference values from both antennas are required for accurate bearing determination, then bearing accuracy is improved, but system complexity increases
Solution Approach 1:
The system creates a copy of the expected phase difference relationship through the tracking filter model. By using the predicted bearing and elevation to estimate what the missing phase difference value should be, the system effectively copies the expected measurement pattern, avoiding the need for complex additional hardware while maintaining accuracy.
Data Source
AI summary
Systems and methods for improving bearing availability and accuracy in a traffic collision-avoidance system (TCAS). In an exemplary method, if only a single phase-difference value is received for one of two two-element antennas, a processor determines an expected maximum antenna element phase-difference value for the elements of the two-element antenna that did not receive a phase-difference value for a target signal source; estimates a phase-difference value for the two-element antenna that did not include a phase-difference value, based on the expected maximum antenna element phase-difference value and a previously determined predicted bearing value; and calculates bearing based on the estimated phase-difference value and a phase-difference value received from the other two-element antenna. The determination is based on previously received signals associated with the target signal source and based on elevation information of the target signal source and a predefined maximum antenna element phase-difference value for the respective antenna element pair. An output device outputs information associated with the calculated bearing.