Measurement of antenna parameters under a controlled temperature Mesure des paramètres d'une antenne sous une température controllée

Antenna design for aeronautical application requires the verification strict environmental conditions with important temperature and atmospheric constraints. The verification of performances of an antenna design is usually performed by measuring its electrical performances before and after thermal and hygrometric cycling to simulate the exposure to outdoor conditions. In this process the impact of temperature variation on antenna gain, radiation pattern or phase, is not tested while it may affect the antenna performance and modify the readout of the associated sensors which are dependent on amplitude of the signal and also on phase information. In particular the design of antennas based on innovative substrate or radome materials may require the validation of environmental withstanding of the antennas in the early design phase. Several solutions have been developed to perform the measurement of antennas under a temperature constraint; most of them involve a low dielectric permittivity enclosure containing the antenna itself. The temperature variation is obtained either by putting some part of the antenna (preferably metallic) in contact with a thermostat at high or low temperature; other solutions are based on the circulation of fluid, especially for cold temperature variations. In this work a thermal enclosure has been developed to test antenna performances at a temperature ranging from 0°C to 50°C. The thermal enclosure is manufactured from extruded polystyrene; it integrates a set of PT100 temperature sensors to measure the temperature grade inside the enclosure. The antenna complex gain is measured at ambient temperature without the enclosure shell and compared to the measurement inside the shell. The temperature variation is obtained by applying an air flux extracted from a laboratory oven. The measurement achieves traceability of the temperature applied antenna and of the antenna parameters through Sparameters traceable measurements. The process is used to measure Commercial Off-The-Shelf (COTS) and may be applied to prototypes.