Aircraft Avionics Research
Investigation of Spurious Emissions from Cellular Phones and the Possible Effect on Aircraft Navigation Equipment
The purpose of this study is to provide valuable information on the spurious emission levels of wireless phones and the possible effect of those emissions on aircraft navigation equipment. The work was designed to be an exploratory study with objectives being the examination of a limited number of aircraft systems, development of measurement procedures, and the early identification of any serious problems. It was not designed to be an exhaustive study of all phone-avionics combinations, but rather an initial exploratory study to identify any significant problems that may exist. The phone technologies tested were: CDMA (Cellular), TDMA 11 Hz (Cellular), TDMA 50 Hz Cellular, TDMA 50 Hz PCS, TDMA 217 Hz, GSM 900, TDMA 217 Hz, and DCS 1800. Emissions of wireless phones positioned one meter from a receiving antenna were measured with a spectrum analyzer. If an emission occurs within the frequency range of a particular aircraft system, and the power of the emissions exceeds the sensitivity of the system’s antenna, the phone could potentially interfere with that system. The phone was placed in a semi-anechoic chamber, one meter from a dipole antenna, and was positioned so that its antenna was oriented vertically upward, while the receiving antenna was oriented horizontally. Scans were then run through five separate frequency ranges, each corresponding to the following aircraft systems: Very High Frequency Communication Omni-Range (VOR), Localizer (LOC), Very High Frequency Communication (VHF), Glide Slope (GS), and Global Positioning System (GPS). In addition, scans were performed in the transmission ranges of the wireless phones. The data obtained from the spectrum analyzer consisted of frequency-amplitude pairs, with the power amplitude given in dBm units. Graphs of the data were constructed to show the results and two levels: the sensitivity of the aircraft antenna associated with that frequency range, and an arbitrary level of 10 dBm below that sensitivity. Analyzing the peak amplitudes of these scans revealed that none of the values exceeded the aircraft sensitivity of any system. The results of this study suggest that, at a distance of one meter from the antenna and in the orientation examined, none of the phones tested would have interfered with the antenna of the aircraft system. Phase II of this study will investigate different relative orientations of the phone and receiving antennas to determine the effects of various polarizations.