Measurements of Aircraft Radio Altimeter Electromagnetic Interference Characteristics Due to 5G Mobile Communication Systems

This paper examines the interference susceptibility of aircraft radio altimeters (RAs) due to Sub-6 5G mobile communication systems under various interference signal conditions. The RAs operate within the 4.2–4.4 GHz frequency range. With the introduction of Sub-6 5G mobile systems in adjacent bands, potential interference issues arise. This study evaluates both in-band and out-band electromagnetic interference susceptibility of 20 RAs. Notably, our measured out-band interference threshold values are over 20 dB which are lower than those reported in the ITU-R M.2059 document.

I. Introduction

Aircraft radio altimeters (RAs) are essential avionics that measure the altitude of an aircraft. This altitude reading is crucial, serving both as a visual confirmation for pilots and an input for various aircraft control systems [1]. These RAs operates within a frequency range of 4.2 to 4.4 GHz. Nevertheless, there is an interference concern because the global frequency assignment for the Sub-6 5G mobile communication system is in adjacent bands to the RA’s frequency. Hence, understanding and ensuring the coexistence of these frequencies is critical for the safety and reliability of RAs.