Measurement of Interference Path Loss between Wireless Avionics Intra-Communications system and aircraft systems at 4.2-4.4 GHz band

Civil aviation is considering the use of wireless transmission technology for safety-related on-board machine-to-machine communications. The crucial factor is the availability of a globally harmonized radio frequency band with predictable characteristics in terms of signal propagation and interference induced by other users of that frequency band. Currently the International Telecommunication Union and the International Civil Aviation Organization are establishing the regulatory environment allowing the usage of the band 4.2-4.4 GHz for so-called Wireless Avionics Intra-Communications. A Wireless Avionics Intra-Communications system essentially provides highly reliable short-range radio links between two or more points on board an aircraft. Since the frequency band 4.2-4.4 GHz is also used for radio altimetry on board civil and state aircraft, it is important to understand the coupling mechanisms between WAIC systems and the Radio Altimeter system onboard the same aircraft as well as onboard different aircraft. For this reason an extensive measurement campaign as described in this paper was carried out. The purpose of this campaign was to assess the degree of coupling between the antennas of both systems for a variety of antenna constellations involving one or two commercial short-haul aircraft of type Airbus A320-200 and A321-200.