Diminishing SAR for Wearable UHF Antennas

This letter presents a study on the specific absorption rate (SAR) evaluation of UHF wearable antennas. A planar inverted-F antenna (PIFA) intended to operate in wireless body area networks (WBANs) is taken as an example for the investigation. The presence of the ground plane introduces isolation between the body and the wearable antenna and decouples the antenna from the body, thus resulting in lower SAR values. The performed analysis of the proposed PIFA indicates increased near-field regions close to the shorting wall, which directly leads to increased SAR values. This can be avoided if alternative current paths are provided, e.g., extending the ground plane slightly. The dielectric materials used as substrates partially reduce the SAR by confining part of the fields inside the dielectric. All the suggested solutions are easily applicable for a practical implementation.