Secondary Near Field RFID Antennas for Wireless Structural Health Monitoring Systems

In this paper it is shown that a conductive feed used to excite a standing surface wave on a metallic object can be used to reliably power a passive UHF RFID sensor tag mounted to the same. The read rates of this method and that of free space are compared. Findings show that along the metallic bar structure, and for a greater distance, minimum read rates were at least 9 times greater than in free space. The maximum read rates were found to be around 20 times larger than in free space. It is shown that by utilizing the metallic structure itself, as a secondary nearfield antenna, it is possible to read accelerometer sensor data effectively from a passive UHF sensor tag such as the WISP 5.0. Such a technique may provide a low cost alternative to traditional SHM systems.