RFID-based passive wireless displacement measurement of metal structures in infrastructure health monitoring

In this paper, radio frequency identification (RFID)-based passive wireless displacement measurement for infrastructure health monitoring is studied. An ultra-high frequency (UHF) RFID section consisting of two antennas is used to measure the displacement of metal structures in which the tag antenna is mounted on metal. It is shown that displacement measurement resolutions of 1 mm and 5 mm can be achieved within λ and 6λ starting distances, respectively, between antennas (Australian UHF RFID frequency band) by changes in the received phase. It has also been shown that displacement measurement resolution of 1 mm can be achieved within λ starting distance using the frequency domain phase difference of arrival (FD-PDoA) method with compensation for reader inaccuracy.