Wearable Dual-Band High-Gain Low-SAR Antenna for Off-Body Communication

A wearable dual-band folded-ring antenna, that has directional radiation pattern and offers high-gain, high-efficiency, and low-specific absorption rate (SAR) performance, is presented for 2.45/3.45 GHz off-body communication. The proposed antenna is comprised of two substrates; a folded-ring antenna as a main radiator is printed on a low-loss rigid substrate and a conductive textile is attached to a felt substrate. The conductive textile is used as the ground plane and as a protective shield to prevent incidental electromagnetic waves from propagating toward the human body. The felt substrate provides a comfortable surface for wearers. The antenna performance is verified and shows very good agreement both in free space and on phantom body environment. The measured bandwidths of S
₁₁
on human body are 5.76% and 4.7% at each frequency band. The maximum broadside gains within the operating bandwidth are 5.1 and 8.6 dB, respectively. The measured radiation efficiencies on human phantom are 91% and 94%, respectively. The SAR values at lower mode based on US and EUR standards under 1 g average and 10 g average are 0.2 and 0.1 W/kg, respectively. At higher mode, the SAR values are 0.1 and 0.04 W/kg, respectively.