A new on-ground-measurement technique for farfield evaluation and possible phased array effects of an aircraft fuselage

With the introduction of GSM-systems on board an aircraft the possibility of phased array effects due to the equidistant arrangement of the windows is discussed in the standardization process. Since a high antenna gain of the aircraft fuselage could cause systems on board to interfere with existing terrestrial GSM networks it is mandatory to exclude the possibility of phased array effects. This paper presents a new measurement technique for such an evaluation measuring the excitation at each window on ground with a later superposition to the farfield. Measurements are presented with a 1:10 scaled, fully metal model of an A320 fuselage with 23 windows. Small antennas inside the fuselage represent mobile phones at different locations. The superposition of the windows' excitation to the farfield is compared with farfield measurements at an open area test site validating the approach of this measurement technique as a substitute for expensive and demanding in-flight measurements. Finally, it is shown that distinctive phased array effects are very unlikely, i.e. can be excluded for practical situations.