A Wearable Circularly Polarized Antenna Backed by AMC Reflector for WBAN Communications

Abstract

A new flexible circularly polarized (CP) wearable antenna is proposed for Wireless Body-Area Network systems (WBAN) operating at 5.8 GHz. The circular polarization is enabled by combining a microstrip-line monopole feed and an inverted L-shaped conformal metal strip extended from a coplanar waveguide. The proposed antenna shows satisfactory performance in terms of gain and specific absorption rate (SAR) at a separation of 12 mm from a human body model. To minimize body-antenna separation, a flexible $2 \times 2$ artificial magnetic conductor (AMC) was used as a reflector to achieve good performances in terms of gain and SAR. The total footprint of the proposed antenna is only $34.4\times34.4$ mm2 ( $0.384 \lambda _{0}^{2}$ ) board of semi-flexible Rogers RT-Duroid 5880 substrate. The final design provides a peak gain of 7.6 dBi and an efficiency of 94.7% when worn on the body. Furthermore, evaluation results indicate that the maximum SAR level decreased by up to 20.42% in comparison with the CP antenna without the AMC. Full-wave EM simulation and experimental results are performed, both in free space and proximity to the human body under different bending scenarios. Overall, the proposed antenna performance has been shown to be robust to structural deformation along the x-axis in comparison to previously reported designs. These features demonstrate that the proposed antenna is a strong candidate for off-body wearable applications.

Keywords

• Wireless body area network
• wearable antenna
• off-body communication
• circular polarization
• artificial magnetic conductor (AMC)