PIM characterization of a deployable reflective surface. Large european antenna application

Abstract

Within the framework of H2020 program, an international Consortium led by German companies HPS and LSS was awarded an EC-grant to develop the first Large European Antenna (LEA). INTA was part of the Consortium with its 15 entities in total and has been in charge of testing activities. Amongst them, INTA carried out the PIM characterization of the mesh structure the LEA is made of. Deployable antennas’ RF-reflective surfaces are commonly formed by complex knitted meshes of gold plated metals. One important issue regarding the RF characterization of this structure is its passive intermodulation (PIM) performance. PIM is a result of nonlinear current versus voltage response. It mostly takes place in weak electrical contact points. Therefore, complex knitted meshes suggest a number of potential PIM mechanisms where environmental variables play an important role: temperature, vibration, relative movement and tension of mesh wires, uncertainty of electrical contact, surface oxidation, etc. As a result of passive intermodulation, part of the energy initially transported by carriers is translated to other frequencies, hence interferences might appear on the transmission-reception system itself, and even on other antennas on board the satellite. A wide testing campaign has been carried out to characterize the LEA mesh. That campaign included the application, on a set of different mesh samples, of extreme thermal cycles, radiated high power levels, under different polarization and incidence angles, vibration, etc., in a zero humidity atmosphere. All tests were performed at INTA’s RF Transparent Low PIM Thermal Chamber, a special facility which grants the feasibility to apply all mentioned conditions. This paper will focus on the techniques applied and on some outcomes that may be useful for the space RF testing community.