Metamaterial-Based Circularly Polarized Wearable Antenna for ISM and 5G Communications

A multiband, small, high gain, low specific absorption rate (SAR), and circularly polarized (CP) textile wearable antenna is designed on a layer of denim (ε
r
= 1.3, h= 0.787 mm) substrate. The antenna is comprised of a rectangular patch that feeds through an inset transmission line and four tilted periodic slots to enhance the bandwidth (BW) and achieve circular polarization. A layer of fleece fabric (ε
r
= 1.04, h= 3 mm) attached to a layer of full ShieldIt to create maximum directivity and minimize SAR value. Then, the antenna is loaded with six arrays of Split Ring Resonator (SRR) on the same antenna layer to enhance the BW that had been reduced after adding the second layer. The antenna works for both ISM and 5G communication systems as it operates at 2.35-2.45 GHz and 3.3-3.9 GHz, respectively. It has the maximum directive gain of 8.52 dBi, acceptable SAR values for both standards with total dimensions of 54 × 56 mm
²
. In addition, the antenna's CP is examined, showing AR values of < 3 dB at the working BW with a decent agreement between the simulation and measurement outcomes.