Study of the Impact of Intermodulation Signals Generated by FM Radio Broadcasting Services (87.5-108 MHz) on the Aeronautical ILS Radio Navigation Receivers of Aircraft.

Abstract

Our research is based on test procedures for measuring the characteristics of aviation receivers used to identify intermodulation distortion generated by broadcast radio transmitters in the frequency range of 87-108 MHz. These distortions create electromagnetic interference that affects aeronautical services operating in the 108-118 MHz radio frequency band. The study analyzes how electromagnetic interference from various sources, including FM broadcast radio services, impacts these systems. This interference generates intermodulation products in the ILS (108–112 MHz) frequency band in the form of third-order intermodulation distortion, which may produce a false deflection signal in navigation receivers within this frequency range. Under such circumstances, the aircraft may receive incorrect guidance signals, leading the pilot to believe that the aircraft is positioned either left or right of the runway centerline. Receiving signals of this category could erroneously indicate a course deviation or result in a complete loss of signal, causing disorientation of the aircraft relative to the runway.