PEDs Emission Determination in a Reverberation Chamber

Portable Electronic Devices (PEDs) are nowadays available on the market and will be potentially used during aircraft °ights. As a consequence a more extensive use of mobile phones, laptop, wireless systems, CD player, etc. is predictable (at least accidentally) in the next few years. Moreover, the bandwidth covered by existing PEDs available on the market is increasing year after year. The main intrinsic features of PEDs which have to be taken into account for the interference problem are the emitted power and the working frequency bandwidth. When PEDs works inside an aircraft, di®erent phenomena occur that give rise to a coupling with antennas and/or electronic equipments through cables and apertures. For this potential coupling risk, the use of PEDs are forbidden during the take o® and landing phases. To make sure that the use of PEDs is under control, it may be useful to install special detectors able to advise for the presence of working devices. A proper design of such detectors cannot leave the PED radiated emission characterization out of consideration. Beside the traditional anechoic chamber test facility, the radiated emission measurement can be carried out inside a reverberation chamber (RC). This situation is completely di®erent from the traditional one, and appears much more meaningful for the type of problem that is being faced: since the orientation of the PED, during its illicit use, is random, also the ¯eld intensity at the detector position will be characterized by this random characteristic. Moreover, inside the aircraft the energy emitted by the PED su®ers several re°ections before reaching the detector. In this sense, the RC is the environment most suitable to reproduce this kind of propagation, because in a ideal chamber the ¯eld can be described as a proper summation of in¯nite plane waves coming from any direction, with any polarization and arbitrary phase. The reverberation chamber quickly provides the radiated power and statistics of the ¯eld without having to rotate the equipment. In this way the measurement procedure is easier. Recently, it has been also demonstrated the possibility to simulate absorption e®ects inside an aircraft using a properly loaded reverberation chamber. For these reasons, an RC has been used to determine the total radiated power of typical PEDs, according to the set-up of Fig. 1. The novelty of the proposed method essentially lies in the power determination, which is independent from the device observation direction. The electric ¯eld determination required the directivity knowledge, which is a deterministic quantity in free space, but assumes a statistic meaning inside an aircraft for the above mentioned considerations. To establish a threshold for a security detection system, the most probable directivity value can be adopted, ¯xing a distance for the detector.