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Session 4: Flight Inspection Technology (including ADS-B and RFI)

Experiences with GNSS Interference in Flight Inspection
Sigurd A. Bjelkarøy, Norwegian Special Mission, Norway
Location: Regency Ballroom
Date/Time: Tuesday, Apr. 17, 9:00 a.m.

The radio frequency spectrum is getting more and more congested with new types of communication signals. These new communication standards are often installed on airports and can with their relative high signal strength cause interference into the GNSS band especially for the flight inspection system multi frequency GNSS receivers.
The paper will explain scenarios where new communication signals have caused interference for GNSS receiver. Even though strict standards are followed to ensure that there are no interference between systems the GNSS system is especially sensitive to interference as the received GNSS itself is very weak. There is a clear difference between standard aviation GPS receivers which are be tuned to a single frequency range and the multi frequency GNSS receivers used for flight inspection.
In some cases the use of multi frequency GNSS systems will improve the position solution in a RF environment with interference but in other cases the wider range of receivable systems makes a multi frequency GNSS more vulnerable for interference.
Now when multi frequency GNSS receivers are becoming more common in aviation use the experiences made in the flight inspection community should be highlighted so it can be known for a broader audience.
The paper will present the issues seen and how they affected the results. Further on it will describe the typical build-up of GNSS systems and where improvements can be implemented to minimize problems. Description on why multi frequency GNSS systems can both be more affected by interference in some cases and less affected by interference in other cases will be presented.
The regulatory requirements for GNSS systems provided in TSO standards, ICAO Annex 10 and radio frequency regulations will be presented and it will be shown why there still are issues with interference even though these requirements are followed.
Since different receivers will act differently to various types of interference the paper will emphasize the importance to record the behavior of standard aviation GPS receivers with standard TSO’d antennas for validation of instrument flight procedures in addition to recording the multi-frequency GNSS signals from flight inspection receivers.
Finally the paper will present possible solutions to how GNSS antennas and receivers can improve it’s robustness to the ever evolving RF spectrum.



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