Passive HF RFID Repeater for Communicating with Tags in Metal Housings

This work presents, for the first time, a custom-built high frequency (HF) radio frequency identification (RFID) system that enables the communication with an RFID transponder (tag), which is attached to an object located in an enclosed metal housing. Proof of concept measurements of the custom-built HF RFID system show a good system performance and a favorable extension of the read range in the metal environment by 19% in comparison to the read range of the free space system. These results are realized by a novel passive repeater structure, which is included in the system (i.e., reader-repeater-tag). The passive repeater consists of an arrangement of two booster antennas and ferrite material. Next to simulation and measurement results, the work provides an equivalent circuit model of the reader-repeater-tag system for system design.