Mitigation of Metal Body Proximity Effect in Magnetically Coupled HF RFID Systems

The deleterious effect of eddy current due to the presence of a metal in magnetically coupled resonant high-frequency radio frequency identification (HF RFID) systems is addressed, and remediation using a resonant loop is discussed. The proposed solution is much more economic than conventional ferrite-based shielding. The resonant loop, which is referred to as auxiliary coil in this paper, does not increase the profile of the existing HF RFID tag. Analysis is carried out using full-wave numerical simulation resulting in an equivalent circuit model, and validated with measurements. The technique is illustrated through applications like HF RFID tags in close proximity to a metal seal required for induction sealing, as well for extending read range of readers compelled to operate near metallic environment.