Secondary Radar Antenna Pattern Measurement Using Fruit Replies
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Solution Overview
Problem
Current methods for measuring antenna patterns in secondary radars require maintenance downtime and external equipment, leading to delayed detection of antenna degradation and potential service interruptions, as measurements are typically done at low elevation angles and infrequently.
Innovation Solution
A method that uses synchronous and asynchronous Mode S replies, specifically Fruit-type replies, to continuously measure antenna patterns in bearing and elevation slices over multiple revolutions, associating azimuth, power, and elevation values to detect and store pattern degradations without additional RF transmission, allowing for continuous monitoring without disrupting radar operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external rig is employed to measure antenna patterns, then measurement capability is provided, but radar coverage is decreased due to maintenance downtime
Solution Approach 1:
The radar system measures its own antenna patterns using existing operational data (synchronous and asynchronous replies) without requiring external measurement rigs or maintenance downtime. The system serves itself by utilizing its own transmitted and received signals to characterize antenna performance.
Solution Approach 2:
The radar system performs multiple functions: it conducts air traffic control operations while simultaneously measuring antenna patterns. The same hardware and operational procedures serve both detection/metrics functions and measurement functions, eliminating the need for separate external equipment.
2Ease of operation
If measurements are performed only at low elevation angles, then measurement simplicity is maintained, but measurement accuracy is degraded for aircraft at typical operating elevations
Solution Approach 1:
The system continuously measures antenna patterns across all elevation angles during normal operational activity. Rather than performing discrete measurements at specific angles, the measurement process occurs continuously as the radar operates, capturing data at all elevation angles simultaneously.
Solution Approach 2:
The system performs preliminary measurements of antenna patterns using existing operational data before any degradation occurs. By continuously monitoring antenna performance during normal operations, the system can detect and report pattern characteristics proactively, enabling preventive maintenance before performance degradation affects air traffic control operations.
3Ease of manufacture
If preventive periodic measurements are performed, then antenna maintenance is scheduled, but detection of degradation is delayed until performance is already compromised
Solution Approach 1:
The system provides continuous feedback on antenna pattern performance by analyzing synchronous and asynchronous replies during normal operations. This feedback mechanism enables real-time monitoring of antenna degradation, allowing maintenance to be scheduled based on actual performance trends rather than fixed schedules or delayed detection.
Data Source
AI summary
An each pattern is provided a reception pathway, the method uses the synchronous replies and the asynchronous replies, unsolicited of Fruit type, transmitted by targets present in the aerial environment of the radar and detected over a given number of antenna revolutions. At each detection of a reply the value of its off-aim in bearing and the value of relative power received on each of the pathways are calculated as is its elevation by extrapolation with the synchronous detections close to the same target and associated with the detection. The values obtained over the given number of revolutions are stored, the measured patterns being sampled on the basis of the stored values.