Thermal testing of small antennas in multi-probe spherical near-field systems

Temperature changes cause thermal expansion of antenna materials and will have an important impact on antenna performances. In some applications, it is sufficient to calculate the antenna deformation by mechanical analysis and determine the RF impact by EM analysis tools. However, if the environmental conditions of the final antenna are stringent and considered critical as in the case of military and civil applications like space and aeronautics, the thermal performance of the antenna must be determined by experiment [1]-[2]. Based on the preliminary results discussed in [3], this paper present a simple and effective method for thermal testing of antennas in a spherical near field range based on multi probe technology [4]-[9]. The antenna is maintained inside an RF transparent thermally insulated container including the local heating and cooling equipment. The fast testing provided by the multiprobe system allows one to measure the temperature dependence of the antenna at several different temperatures within the investigation range. The method will be illustrated for the cold measurement case with temperatures below -100°C but the extension to the full cold to hot temperature range is trivial.