Analysis of wearable ungrounded antennas for UHF RFIDs with respect to the coupling with human-body

A number of wearable antennas suitable for implementation of UHF-RFID tags have been presented in the open scientific literature. All of them are characterized by a high sensitivity with respect to the coupling with the human body, both on the input matching and on the antenna efficiency. This work presents a numerical investigation performed over a couple of wearable, ungrounded, antennas configurations, which shows that their robustness can be related to the distribution of the electric and magnetic energy densities close to the antenna borders