Design Considerations on the Placement of a Wearable UHF-RFID PIFA on a Compact Ground Plane

The robustness of wearable antennas to the human body proximity can be improved by properly placing the radiating element over a ground plane, or by shaping the ground plane, on the basis of the antenna electric and magnetic energy density distributions, aiming to confine the electric energy density in specific regions far from the antenna border. The effectiveness of the above design criterion has been assessed through both numerical analysis and experimental measurements, by optimizing the position of the radiating element of a wearable grounded ultrahigh frequency radio frequency identification tag operating at the ETSI band (865-868 MHz), with respect to its ground plane. A flexible tag characterization and performance evaluation platform is used to measure the tag sensitivity as a function of the antenna-body distance.