ILS Overflight Interference Mitigation via Hybrid Positioning
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Solution Overview
Problem
Instrument landing systems (ILS) face interference from multipath effects during aircraft overflight, causing distortion in guidance signals and potentially leading to unwanted lateral movements of aircraft, which existing technologies have not adequately mitigated.
Innovation Solution
The method involves performing multiple measurements of an aircraft's position using a combination of ILS and inertial navigation systems, with inertial measurements integrated over different time periods to select and generate guidance information, thereby mitigating overflight interference by translating lateral deviations into a rectilinear runway reference frame and correcting for bias errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ILS signals are used for navigation guidance, then lateral navigation guidance is provided, but multipath interference from aircraft overflight causes signal distortion and false lateral deviation indications
Solution Approach 1:
The patent combines ILS position measurements with inertial navigation system (INS) measurements to create a hybrid positioning system. The INS provides independent position data that is not susceptible to multipath interference, and by merging both measurement sources, the system can detect and mitigate the harmful effects of multipath interference on ILS signals.
Solution Approach 2:
The inertial navigation system acts as an intermediary between the ILS receiver and the guidance system. By comparing ILS position measurements with INS-derived position measurements, the system can identify multipath interference and select the more reliable measurement, thereby mediating the harmful effect of signal distortion.
2Reliability
If multiple position measurements are performed using different time periods, then overflight interference can be mitigated, but device complexity increases
Solution Approach 1:
The system dynamically adjusts the time period over which inertial measurements are integrated based on flight conditions and interference detection. By making the measurement window adaptive rather than fixed, the system can improve reliability during interference events while maintaining simpler operation during normal conditions, thus balancing reliability and complexity.
Solution Approach 2:
The system automatically selects between different measurement sources (ILS vs. INS-derived positions) based on detected interference conditions without requiring external intervention. The multi-measurement approach enables the system to self-diagnose multipath interference and self-correct by selecting alternative position data, thereby improving reliability while the automation minimizes the operational complexity burden.
Data Source
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AI summary
Systems and methods to mitigate instrument landing system (ILS) overflight interference are disclosed. An example method performing a first measurement of a position of an aircraft relative to a first location based on an instrument landing system, performing a second measurement of the position of the aircraft based on inertial measurements performed over a first time period occurring prior to the first measurement, performing a third measurement of the position of the aircraft based on inertial measurements performed over a second time period greater than the first time period and occurring prior to the first measurement, and generating guidance information based on a selected one of the first, second, or third measurements of the position of the aircraft.