Mode S Secondary Radar BDS Swap Mitigation via Intermediate Noise Window Verification
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Solution Overview
Problem
BDS swapping occurs in Mode S secondary radar systems, leading to incorrect data usage, erroneous changes in aircraft tracking, and potential loss of track due to incorrect positioning, which affects the effectiveness of air traffic surveillance.
Innovation Solution
A method for managing secondary radar systems that includes an intermediate step between seeking and tracking modes, where the presence or absence of the aircraft reply is detected in a noise window, and additional roll-call interrogations are conducted using the first monitoring window if the reply is not located in the noise window, thereby addressing BDS swapping issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the radar uses a large monitoring window in seeking mode to cover prediction uncertainties, then the detection reliability is improved, but the productivity decreases due to extended interrogation time
Solution Approach 1:
The patent applies dynamics by transitioning from a static large monitoring window in seeking mode to a dynamic window adjustment mechanism. After detecting the aircraft reply, the system calculates a new monitoring window based on the actual reply position and reduces the window size for subsequent interrogations in tracking mode, optimizing the balance between detection reliability and interrogation efficiency.
Solution Approach 2:
The patent segments the operational mode into two distinct phases: seeking mode with a large monitoring window for initial detection, and tracking mode with a reduced monitoring window for subsequent interrogations. This segmentation allows the system to optimize parameters for each phase separately, improving overall productivity while maintaining reliability.
2Productivity
If the radar switches to tracking mode with a reduced monitoring window, then the productivity is improved, but the reliability deteriorates when BDS swap occurs causing incorrect positioning
Solution Approach 1:
The patent implements feedback by continuously monitoring the position of received replies and using this information to adjust the monitoring window. When a reply is detected outside the expected window (indicating BDS swap), the system uses this feedback to recalculate and expand the monitoring window, ensuring reliable detection while maintaining high productivity through the reduced window in normal operation.
Solution Approach 2:
The patent applies preliminary action by performing an intermediate step before fully transitioning to tracking mode. The system conducts additional roll-call interrogations using the first monitoring window to verify the aircraft reply position before committing to the reduced second monitoring window, preventing BDS swap errors from affecting positioning accuracy.
3Reliability
If the radar locks out the transponder for eighteen seconds, then the reliability is improved by preventing false replies, but the loss of time increases due to the lockout duration
Solution Approach 1:
The patent applies preliminary action by conducting verification interrogations before the lockout period. The system performs additional roll-call interrogations in the first monitoring window to confirm the aircraft reply and ensure correct positioning before the 18-second lockout begins, reducing the effective lockout time impact while maintaining reliability.
Solution Approach 2:
The patent maintains continuity of useful action by overlapping the verification interrogation process with the lockout period. The system continues to conduct useful interrogations and monitor replies throughout the lockout duration, ensuring that the lockout time is minimized while still preventing false replies and maintaining tracking reliability.
Data Source
AI summary
A a method for managing a secondary radar operating in Mode S, the method includes a) a detection in “seeking mode”, the “seeking mode” being implemented until an aircraft is detected by the secondary radar; b) a detection in “tracking mode”, the “tracking mode” being implemented if a valid response to a roll-call interrogation was detected in “seeking mode”; the method comprising an intermediate step a1), which is executed between the detection in “seeking mode” and the detection in “tracking mode”, the intermediate step comprising: detecting the presence or absence of the reply of the aircraft in a noise window of the secondary radar; carrying out at least one roll-call interrogation, using the first monitoring window, if the reply of the aircraft is not located in the noise window.