Millimetre-Wave Interrogation of Passive Sensors Embedded Inside Closed Reverberant Environments from Dual-Polarized Passive Repeaters

For testing satellites before launching, multiple wired sensors are commonly used for covering the metallic walls of the inner satellite structure. In order to reduce the maintenance cost of such Structure Health Monitoring platform, wireless sensors could be advantageously used. In this paper, we demonstrate the reading feasibility of passive and wireless millimetre-wave sensors embedded inside an over-sized metallic box. The box simulates here a part of the electromagnetic reverberant environment within satellite structure. In the proposed cross-polarized configuration, a dual-polarized passive repeater is used for transmitting inside the box the co-polarized electric field radiated by a Frequency-Modulated Continuous-Wave 24GHz radar. This repeater is also used for transmitting outside the box the cross-polarized electric field radiated by a depolarizing sensor. The proof-of-concept is established here from a passive and chipless pressure sensor, but other types of wireless sensors may be used as well.